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science, and it is sure to be no less popular among older (Carapa guianensis, a native of tropical America and people who appreciate a sound and easy guide to the west tropical Africa, does not appear to inhabit the tidal mysteries of practical electricity.

forests); Myrsineæ-Ægiceras; Rubiacea-Scyphiphora; In taking leave of this work, we have only to say, what Verbenaceæ–Avicennia (both in the Old World and in has already been indicated above, that an extension of America) ; Acanthacex-Acanthus ilicifolius; Palmæthe editorial remarks, and their absorption into the general Nipa fruticans. current of the text, with consequent re-writing of some The foregoing are the principal and widely-spread of the chapters, would render it more homogeneous, and trees and shrubs of the mangrove girdle of muddy throughout more in accordance with the electrical spirit tropical shores; but this list might be largely augmented of the age. Still, the clearness of its arrangement and if we included those forming the tidal forests of the Bay style more than compensate for the disadvantages of Bengal, and similar situations. Thus, in the Sundernecessarily attending an edited English edition of a bun, as Mr. C. B. Clarke informs me, the Sundra tree foreign scientific treatise, however popular. As a whole, (Heritiera Fomes) abounds to such an extent that a railit reflects credit on all concerned-translators, editor, way is almost entirely devoted to carrying the wood to and publishers alike. Its publication may even do some- Calcutta, of which city it is the fire-wood. Among other thing towards arousing an interest in electricity in circles, common trees and shrubs are Hibiscus tiliaceus, Sapineven in this proverbially practical country, where the dus Danura, Dalbergia monosperma, Derris uliginosa, light of science can hardly be said to have yet penetrated.Oxystelma esculentum, Dolichandrone Rheedei, Premna

A. GRAY. integrifolia, Clerodendron inerine, Pandani, Phænix

paludosa, and Cocos nucifera. Mr. Clarke further inforins

me that the milk of the coco-nut in the Sunderbun is BIOLOGY OF SEASIDE PLANTS.

so salt as to be undrinkable. This is a very remarkable Die indo-malayische Strandflora. Von A. F. W.

fact, and scarcely in harmony with the observations of Schimper. Mit 7 Textfiguren, einer Karte, und 7 Schimper, Karsten, and others, so far as mangrove plants Tafeln. (Jena : Gustav Fischer, 1891.)

are concerned generally. Ueber die Mangrove- Vegetation im malayischen Archi- In this connection it may be mentioned that mangrove pel. Von G. Karsten. Bibliotheca Botanica, Heft 22. plants have mostly very thick leaves, with few, very (Cassel : Theodor Fischer, 1891.)

deeply seated stomata, so that transpiration is reduced CHESE two essays are exceedingly interesting con

to as low a minimum as in true xerophytes. As it is TH

tributions to our knowledge of plant-life on tropical obvious that transpiration is not checked in halophytes sea-shores. They partly cover the same ground, partiy because of a lack of water, it must be accounted for in supplement each other, and to some extent review and

some other way; and, as it has been found that the summarize the work of previous observers. Schimper

accumulation of salt in the tissues of the leaves beyond a treats of the salt-loving plants of the sea-shore generally, certain quantity, varying in different plants, prevents the whilst Karsten's investigations are limited to the purely formation of starch and glucose, it is assumed that it is mangrove vegetation. Karsten also enters more fully of a protective character ; that, in short, smallness of into the formation of seed;—that is to say, into the de

transpiration means smallness of absorption, and thus velopment of the embryo-sac, the endosperm, and the

no more salt is taken into the tissues of the plant than it embryo ; and he follows up their germination and is capable of assimilating. The correctness of this view subsequent growth.

is strongly supported by the fact that mangroves, grown But the object of this notice is to give some general in soil free, or practically free, from chloride of sodium, idea of the subject rather than a critical exposition of the develop foliage of less substance, furnished with a writings of the authors named, for they are the first at larger number of stomata. tempts at a connected description of the vegetation of

Turning to another phase in the life-history of mantropical sea-shores.

groves-namely, reproduction-we find special provisions, The mangrovel vegetation--that is, the vegetation of the

suitable to the exceptional conditions, to insure the protidal forests-exhibits comparatively little variety, though pagation of the species. Most of the members of the the components belong to several different natural orders. Rhizophoreæ, for instance, are, in a sense, viviparous-First come the Rhizophoreæ-genera Rhizophora (both

that is to say, the seed germinates on the parent plant. in the Old World and in America), Bruguiera, Ceriops, and when the seed is ripe, the radicle, or primary root,

Only one ovule is developed, the rest being aborted ; and Kandelia ; Combretaceæ–Lumnitzera (Laguncularia in America); Lythracea-Sonneratia ; Meliacez-Carapa grows through the apex of the fruit, assuming a slender

club-shaped form, with the centre of gravity nearest the * The word mangrove looks quite English, but it appears to be a corruption organic base, so that, when it eventually separates from or modification of mangro or mungro, the name commonly applied, accord. ing to Rumpf (1750), and Blume Museum Botanicum, i. p. 132), in Dutch the parent, it falls in such a manner that the radice Guiana to Rhizophora Mangle. However, it was employed in its present form by Dampier, Sloane, and other writers of the seventeenth century, and

penetrates the mud, and usually sufficiently to withstand it is now applied to a number of different trees and shrubs that constitute the ebb and flow of the water. The size and length of the outermost fringe of vegetation on tropical coasts. designate these shrubs and trees collectively: Mangi-mangi is the generic the viviparous radicle varies considerably in different term in the Malay Islands for these trees and shrubs, and the different kinds are distinguished by affixes. In Brazil, Rhizophora Mangle is called mangle

genera, and even in different species, of the same genus, aud mangue; and in Pinama, on the authority of Suem unn ("Die Volks- attaining its greatest development in Rhizophora mucron men der amerikanischen Pflanzen"), the former name is current, with various qualifying affixes. In Grisebach's list of colonial names of plants

nata, the forepost of the Asiatic mangroves, and perhaps ("* Fiora of the British West Indian Islands," p. 785). we find maagrov: (Rhizophora mingle); black mingrove (Avicennia nitida): white mangrove

the only one that sometimes grows where the soil is (Laguncularia ricemosa); and Zaragoza mangr ve (Conocarpus erectus). always submerged. In this the viviparous radicle is

It is also used to

usually from twenty to twenty-four inches long, and by judicial moderation and impartiality; and many amoccasionally as much as forty; and it is capable of biguities and obscurities, due to the defects of Ricardo's growing even should it fall where it is wholly under style, are cleared away. Naturally, the abstract theory water in the early stage of its further development. of value is treated first; and here the editor acknowWhen the young plantlet is ready to separate from the ledges that Ricardo did not attach sufficient importance parent, the aperture made by the growing radicle is to the influence of demand in determining value. But, sufficiently large to allow the inclosed or apical end on the serious question of the relation of capital to labour, to slip out, leaving the empty fruit still attached to the he hardly seems to make Ricardo's position clear. He branch. And when this happens, there is a fully-formed says (p. xxxix.) :leaf-bud at the top, from which the stem is developed.

“Of course, the mere fact that capital is subject to The primary root does not grow much after falling, but such replacements enables us to assert that, in the long stout secondary roots are thrown out from this axis, run, there is a tendency to some equality of reward besuccessively, one above the other; and as they assume tween indirect labour (i.e. labour embodied in capital) an arched form, and are produced in all directions, the

and direct labour. Thus in a somewhat abstract and plant becomes very firmly fixed. The American Rhizo general way we may renew our previous statement that

commodities exchange in the ratio of their cost of phora Mangle is very closely allied to the Asiatic and

production." African R. mucronata; but whereas there is only one genus and one species of the order in the New World,

This passage, in which the editor concludes his general there are several in the Old.

criticism of Ricardo's theory of cost of production, appears Singular to say, the only herbaceous plant of the to involve the very fallacy that some Socialists have Asiatic mangroves, Acanthus ilicifolius, is surser:cd by committed in their reasonings based on Ricardo. For it similar stilt-roots. Most of the other trees and shrubs of suggests their doctrine that capital is nothing but labour the mangrove vegetation have horizontal roots, often of applied indirectly to production. Now Ricardo most enormous length and strength, and some of them produce explicitly avoided this fallacy. He wrote (p. 27) :the so-called knee-roots in great abundance. These “On account of the time which must elapse before one roots grow out of the ground, at an angle of about 45°, set of commodities can be brought to market, they will to a height of a foot or two, or perhaps more, and be valuable, not exactly in proportion to the quantity of return to the ground at about the same angle, forming an

labour bestowed on them, . but something more to anchor-like attachment. But their function is not merely elapse before the most valuable can be brought to

compensate for the greater length of time which must to hold the plant. Thcy are abundantly furnished with market.” lenticels, through which the interchange of gases takes place—at least, such is the opinion of several eminent

In short, Ricardo distinctly points out that an additional physiologists. Indeed, Karsten designates them breath value arises when the same quantum of labour is extended ing roots. Schimper figures negative geotropic roots of

over a larger period of time. Avicennia tomentosa, which grow quite erect, from a

On the question of the distribution of reward between thicker horizontal root, to a height of about a foot, and are

capital and labour, the editor remarks (p. xxxviii.) :either undivided or forked, and taper to a point. They “The two great agents in production-labour and are thickly studded with lenticels, as are the stilt-roots of capital—so divide total value between 'them that an Rhizophora. Another modification of root-production is increase in the value obtained by the one implies a exhibited by some of the mangrove-trees. Like Rhiso

diminution in the share of value falling to the other." phora, they produce aërial roots ; but, instead of their This apparently harmless truisin is elaborated with remaining free, they eventually grow to the stem and painful prolixity. But the form in which Ricardo apoutwards, forming plate-like buttresses.

plied it was always “ Profits depend on wages ”- never Many other interesting facts might be extracted from “Wages depend on profits.” With Ricardo, profits were the papers cited ; but enough has been said to give an the residue of production remaining over and above the idea of the nature and value of their contents.

value of the standard of confort; and he did not enter W. BOTTING HEMSLEY. too closely into the question of the forces determining

variations in this standard. This crucial error shows.

itself throughout all Ricardo's reasonings--notably in RICARDO'S POLITICAL ECONOMY."

his theory of taxation. Principles of Political Economy and Taxation. By David

In Appendix B, the treatment of the effects upon rent Ricardo. Edited, with Introductory Essay, Notes, and of improvements in the fertility of land is very unsatisAppendices, by E. C. K. Gonner, M.A., Lecturer on

factory. The editor says that Ricardo made two assumpEconomic Science, University College, Liverpool. tions-one implicitly and the other explicitly. But if he (London: George Bell and Sons, 1891.)

had properly interpreted the assu

terpreted the assumption explicitly made, HIS edition of Ricardo's “ Principles" will be found he would have seen that the other was unnecessary.

to a large number of footnotes, the editor contributes an improvement is assumed not to disturb “the difference introductory essay of forty pages, and two short ap- between the productive powers of the successive portions pendices—(1) on Ricardo and his critics, (2) on the effect of capital.” The editor most gratuitously interprets difupon rent of improvements in the fertility of land. The ference to mean ratio, in the face of the fact that all introductory essay gives a general account and brief Ricardo's illustrations assume constancy of difference, critical estimate of Ricardo's work. It is characterized not constancy of ratio. Now Prof. Marshall has shown that, with Ricardo's premiss, his conclusion is absolutely vitality. In all his books he is especially interesting in correct without any further assumption. If, on the other passages dealing with the habits of animals, and there hand, we adopt constancy of ratio (instead of constancy

are many such passages in the present volume. No of difference) —which was Mill's (not Ricardo's) supposi- only of things which he himself has had opportunities of

secondhand information is offered; the author tells us tion—then some further assumption must be made in noting. Most of the chapters have already appeared in order to demonstrate that improvement in fertility pro- | Blackwood's Magazine, but many who read them there duces diminution of rent. in proving this point, the will be glad to possess them in their present form. The editor uses an unnecessarily complicated piece of mathe- manuscripts of the “Son of the Marshes" have, as usual, matical reasoning.

been edited by Mr. J. A. Owen, who does not say precisely

how much his editorial work includes. Without further dwelling on these defects, it is only necessary to say that the explanatory footnotes are every- | Heroes of the Telegraph By J. Munro. (London: where extremely helpful, and that the frequent references Religious Tract Society, 1891.) to Ricardo's “ Letters to Malthus ” will be found espe. The author of this book desires that it shall be regarded cially useful in further elucidating the great economist's as in some respects a sequel to his volume on “Pioneers doctrines.

W. E. J.

of Electricity." He begins with a short account of the origin of the telegraph, and then sketches the lives and principal achievements of those discoverers and inventors

to whom we owe the electric telegraph and the telephone OUR BOOK SHELF.

Charles Wheatstone, Samuel Morse, Sir William Photographic Pastimes : a Hand-book for Amateurs. Thomson, Sir William Siemens, Fleeming Jenkin, J. P. By Hermann Schnauss. Translated from the Second

Reis, Graham Bell, Thomas Alva Edison, and D. E. German Edition. (London : Iliffe and Son, 1891.)

Hughes. In an appendix, Mr. Munro gives brief accounts MANY and varied are the effects that can be produced connected with his subject. He has a plain, straight

of various other investigators whose names are intimately with the aid of the camera, and the present work gives a forward style, and the book will give much pleasure to plain and popular account of the methods that have been young readers who take interest in the practical applicaadopted in producing them. The five chapters are tions of science. headed, respectively — specialities, curiosities, photography by peculiar arrangements, photographic optical entertainments, and entertainments with photographic prints.

LETTERS TO THE EDITOR. In carrying out the experiments contained under the [The Editor does not hold himself responsible for opinions exfirst two headings, amateurs will find their time fully oc- pressed by his correspondents. Neither can he undertake cupied, while the novel effects that can be obtained will to return, or to correspond with the writers of, rejected afford both instruction and amusement. With reference manuscripts intended for this or any other part of NATURE. to taking pictures by moonlight, we can quite agree with No notice is taken of anonymous communications. ] the author when he says that “if the moon is included

The Koh-i-Nur. in the picture, its track will make a straight band of light nearly half-way across the photograph, which, besides DR. BALL, in his reply (NATURE, vol. xliv. P: 592) to my the peculiar illumination of the landscape, gives a most

criticisms on his “true history”of the Koh-i-Nur, feels aggrieved characteristic effect.” The characteristic effect, we should

that I "smite him in season and out of season," and considers think, would be very decided.

me in the light of a partisan for doing so. I can assure him An excellent and easy method of producing ghosts, that my criticisms were absolutely impersonal, as I have never, which may prove useful to amateurs, and which is not natured feeling towards him ; indeed, I said whatever I was wholly described in this book, is as follows :-The ghost able honestly to do in favour of his work. But of course, where consists of a person completely covered over with a sheet, I considered his arguments to be groundless or illogical, I met the latter being so adjusted as to give a dim outline of them. If he has read into my remarks an asperity I did not the head ; when in position, a short exposure of about desire to impart to them, surely he should blame himself somehalf an inch of magnesium is given : then, as soon after what for the style of his attacks on those who went before him, wards as possible, without moving anything with the and of whom I have shown that they knew not less, but more, exception of the ghost (which now is no longer required), of the subject than he did himself. another exposure is made, by means of a magnesium flash

I have pleasure in withdrawing my expression of an accusation light, of the other figures that are required for the picture.

that Prof. H. H. Wilson was one of those against whom Dr. In this manner excellent results have been obtained, the

Ball threw out a sneer in relation to the earlier history and pattern on the wall appearing through the ghost, giving it

traditions attaching to the Koh-i-Nur. I supposed that, as quite a realistic appearance.

he has laboured to make his knowledge of the authorities

on the subject complete, he would certainly have known what In these and the remaining chapters, descriptions of

was of common knowledge at the time as to the authormany novelties too numerous to mention are given, of ship of by far the most interesting notice ever penned on which the following may serve as types --caricature, the Koh-i-Nur. But that was long ago. It was that notice, composite, and pin-hole photographs, statuary portraits, however, that brought me into such contact as I have had with kaleidoscopic and stroboscopic pictures, &c.

the subject. As a young Professor at Oxford, I had the honour Altogether, amateurs will find in this hand-book much of knowing the great master of Sanskrit and of Indian lore : that will occupy them during the winter months, when and as I had been interested in Indian history I ventured to out-door photography is more or less at a standstill.

approach him now some thirty-five or thirty-six years ago on

the subject of the values assigned by him to certain weights On Surrey Hills. By a“ Son of the Marshes.” (Edin- referred to in his article. I drew his attention to Babar's valuaburgh and London : W. Blackwood and Sons, 1891.)

tion of the mishkal in ratis, and I further pointed out the prob

ability of the retention by Shah Jahan of the Mogul diamondin THE Surrey hills are so well known that an ordinary | his captivity. He received my suggestions in the kindest spirit. writer would find it hard to say anything fresh about them. and offered me every help in further inquiry ; and at the East The “Son of the Marshes,” however, has an exception- India Company's Library he placed all the documents before me. ally good power of observation, and even familiar facts he I shall not weary your readers with thrashing out and again is able to present in a way that seems to give them new winnowing the various statements involved in this controversy.

ornament.

I could say more about the Garcias-De Boot matter, but I am was more probably its original form rudely facetted (and I think, satisfied with having shown that it was not Dr. Ball, but Mr. perhaps, I may not be without a mineralogist's experience when King, who, twenty-five years ago, explained the misprints in I say ihis); I further say that the Darya-i-Nur is undoubtedly De Boot, and declared the very great inprobability of the 140 the" Golconda table" diamond. mangelin diamond of Garcias, estimated by De Boot at a weight Finally, I assert the probability that the Great Mogul, unof 1875 carats, not being the Koh-i-Nur. Dr. Ball alludes to whittled down and entire, is in the jewel chamber of the Shah of inaccurate figures in Mr. King's treatise. That Mr. King was Persia to this day. inaccurate, was hasty, no one knows better than I. Nor did of the great diamond which I would identify with this stone any of his many warm friends lament more than I did the unhappy I append a tracing, in which it is seen in its carcanet of ruby infiction of advancing blindness which explains so much of the enamel. In the original drawing it is accompanied to right and former demeril, as no one admired more than I the boy-like left by two large diamonds, similarly girdled; while, above and enthusiasm which often gilded in his imagination what seemed below, is a row of three enormous rubies encircled by emeraldto others metal of a less precious order than gold. He had a enamel. Ten pearls above and ten below, some of them of an splendid memory, and he trusted too much to it in drawing out inch in diameter, form a fringe to this gorgeous ornament.

It from it, rather than throwing on his impaired eyesight, the verifying the records of his enormous reading and varied knowledge. I had controversies with him over a thousand subjects, but while he kept singularly isolated, and let no one come between him and his printer, he never resented a friend's criticism or difference from him.

As regards the scene before the throne of Aurungzebe, it can never, perhaps, be determined whether the view first put forward by Prof. H. II. Wilson, that Tavernier weighed the diamond, but with weights and scales supplied by Akil Khan its custodian, is the correct one; or the view I have heldnamely, that Tavernier's account of the transaction given in his tenth chapter was barely compatible with his having weighed the stone, as he asserts he did in the twenty-second chapter of his book, which was avowedly a retrospective one written long afterwards, and near the end of his life. That I have reason for adhering by preference to the latter view is confirmed by what Dr. Ball himself says of another passage referring to the Great Mogul diamond. Dr. Ball condemns the passage as "in part spurious if not altogether so, . . . as the statements are in coniradiction with others made elsewhere in the 'Travels'; and there is the

Fig. 1.-Great Mogul. strongest reason for attributing them to an erroneous editorial interpretation, aud not to Tavernier himsell.” The delinquent he supposes to have been a M. Samuel Chappuzeau, the reputed is, however, only one half of a cylindrical cap the correspondeditor of Tavernier's works.

ing half of which is its counterpart in splendour and wealth of As a fact, the travelled Frenchman seems to have been a

stones, only the Darya-i-Nur is in, that other half, the central person somewhat illiterate, as he had to call in extraneous aid in putting his memoirs into shape. He must be supposed to

I leave the great stone to speak for itself in the tracing, and have picked up some colloquial Persian, but otherwise seems |

I furthermore for comparison give a tracing from a drawing of to have been dependent on interpreters throughout his travels.

the Koh-i-Nur, taken from a somewhat similar point of view The treatment Chappuzeau received during a year of editorial

—that is to say, looking down on it. service at the hands of Tavernier and his wife is recounted

That the Koh-i-Nur was valued beyond these greater stones by Dr. Ball as a sort of “mortification, if not martyrdom.”

I believe to have been in consequence of its being the reputed Chappuzeau appears to have described the notes of the traveller,

talisman of Indian empire. It was probably that last relic on which he had to depend, as a chaos, and to have attributed of his treasure surrendered by the miserable Muhammad Shah the only written part of them to the permanship of one Father

when he exchanged caps with Nadir, and the conqueror saluted Gabriel. I think I am justified, then, in asking whether the

this most historic of his spoils by the name it has since borneaccount of the weighing in the later chapter may not have been an editorial afterthought; but whether it were so or was historical, in the sense assigned to it by Prof. Wilson, really very little affects the question.

The logical issue of this discussion is involved in tbe acceptance of one of two alternatives, the one a series of astounding coincidences and improbabilities, the other one of simple probabilities. Garcias saw a diamond weighing 140 mangelins; Le Cluze estimated its weight at 700 apothecary grains ( = 573:8 grains troy, or 180 carats). De Boot assigned to it a weight of 187) carats. The Koh-i-Nur weighed 589. grains, or 186 carats. Misinterpreting a note of Le Cluze, Dr. Ball throws scorn on this having anything to do with the Koh-i-Nur. Tavernier sees a diamond to which a weight is assigned of Babar's diamond (the Koh-i-Nur) weighed 8

Fig. 2.--Koh-i-Nur. mishkals, or 320 ratis, equivalent to about 186 carats. Dr. Ball says this diamond was that known as the Great Mogul, that it the Koh-i-Nur. It was certainly the diamond that Shah Rukh, is ihe Queen's Koh-i-Nur, but that it was whittled down by alter yielding up all his wealth of jewellery, held to through every necessitous princes--to find them, in fact, in pocket-money- torture till he gave it to Ahmad Shah. Shah Zaman carried it from 280 carats to 589) grains, or 186 carats, the identical to his prison, and secreted it in a crevice ; whence Shah Shuja weight of Babar's diamond and of the Koh-i-Nur. Dr. Ball recovered it on information from his blinded brother. finally declares the Darya-i. Nur to have this same weight of Shah Shuja again clung to the old talisman not less fiercely 186 carats.

than those who had preceded him, till he surrendered it to In opposition to this impossible recurrence of coincidences I Runjit Singh under pressure which amounted to compulsion ; have endeavoured to show that the stone Garcias saw may have and memorable was the answer of Shah Shuja to Fakeer Nurbeen the Koh-i-Nur, that the one Tavernier handled was in all | ud-dín, who had been sent by Runjit to ask in what its value probability-I believe was certainly—the Koh-i-Nur. I say there consisted. It is “good luck,” said Shah Shuja, " for he who is no evidence whatever of the Koh-i-Nur having been whittled has possessed it has done so by overpowering his enemies." down by cleavage, accidental or intentional ; that its form in 1851 I have put, I hope clearly, to my readers, the alternative and

319-5 rati,

case.

cwflicting interpretations of the portion of the accounts of the what indistinct, but at all events the luminous band extended Koh-i-nur from Babar's time onward. There are still some east and west almost through the zenith, and was preceded by interesting questions of a difficult kind regarding its history an auroral display. It occurred in August or September of antecedent to the days of the Mogul Empire. But I believe I 1883 or 1884. have said now my last word regarding the later history, and My attention was again directed to a similar appearance on leave to my readers the decision as to the side in this little the evening of September 9 of the present year, while near controversy on which the truth is more likely to lie.

Toronto. The narrow band of light, as before, extended from

N. STORY MASKELYNE. the eastern almost to the western horizon, passing through the Basset Down House, October 26.

zenith, and was accompanied by an aurora.

It is worthy of note ihat I saw the phenomenon at Toronto on

the evening of September 9, not September 11. A Rare Phenomenon.

R. N. HUDSPETH. AURORAS were visible at Lyons, New York, on September

Bishop's College, Lennoxville, P.Q. 9, 10, and 11. That on September 9 was very fine, fickering streamers and arches forming at intervals from 8 o'clock to 10 o'clock. p.m. A peculiar feature of this aurora was an arch

Apparent Size of Objects near the Horizon. similar to that described in NATURE of September 17 (vol. xliv. Some years ago there appeared an account of an investigation p. 475), as having been seen by Mr. Tuckwell at Loughrigg, into the cause of the sun and moon looking larger when low Ambleside, on September 11. The arch seen at Lyons on down than when high up in the sky. The theory advanced as September 9 was visible shortly after sunset, and remained in the result of the investigation attributed the effect to a physio. the same position throughout the evening. It consisted of a logical cause. One could not expect an explanation of this kind narrow band of light, which arose vertically from a point on the to be applicable to all individuals, but rather that with different horizon nearly due west, and passed through the constellations persons there would be different results ; so I have made obserof the Northern Crown and the Lyre, and just south of the vations—81 in number-to find out what law applies to my own zenith down to the eastern horizon. When it was brightest, at These observations were made by taking notice of two about 10 p.m., a few small streamers formed in connection with stars near the horizon, and then looking up near the zenith to see it nearly in the zenith ; otherwise it consisted simply of a narrow what stars in that situation appeared to be the same distance band of white light separated by a wide interval from the apart as those near the horizon. I took a great variety of auroral coruscations and streamers in the northern heavens. different cases, the length of the compared arcs varying from This seems to have been very similar to the band seen by Mr. 1°4 to 100°. I observed them also in various angles of position, Tuckwell. Other instances have been noted by the writer in from horizontal to vertical ; and sometimes had the two arcs at wbich some peculiarity of form or colour characteristic of an the same angle of position upon the retina, and at other times at outbreak of the aurora has attended its appearance in localities different angles. remote from each other.

M. A. VEEDER. The result of this investigation is an unexpected one, showing Lyons, N.Y., October 17.

that the length of the observed arc greatly affects the result of

the estimation-sbort arcs appearing longer when near the Two instances of the occurrence of the rare phenomenon horizon than when high up, and long ones appearing shorter. referred to in your issue of September 24 (vol. xliv. p. 494),

The comparisons were made in either of two ways; according by Prof. R. Copeland and Mr. W. E. Wilson, will be found

to one method, aíter I had carefully taken note of the aprecorded in the Transactions of the Nova Scotian Institute of parent length of the arc near the horizon, and had fixed an Natural Science, vol. vi. p. 100. The dates of these occur

idea of it in my mind, I then took a single glance at the stars rences were July 31 and September 5, 1883. The general

near the zenith and fixed in a moment upon an arc that appeared appearance and position of the luminous arch were the same in to be of the same length ; whereas in the other plan I made as both cases as in those described by Prof. Copeland and Mr. Wilson.

deliberate and careful an estimation of the arc near the zenith as Two additional points were noted, however, which are worthy of that near the horizon with which it was compared, looking to of mention, viz. (1) that the arch of September 5 had a slightly and fro from one to the other till I was satisfied as to their marked rayed structure, which, when first observed, was in the apparent equality. direction of its length, but which gradually changed to a direc

One would naturally expect that the instantaneous estimations tion inclined about 45° to the longitudinal, and (2) that the would be less accurate than the careful ones, and this is found to spectrum of this arch, as determined by one of Hilger's pocket deviation from the truth of a single estimation is 7'7 per cent. in

be the case. Taking all the observations, I find the average spectroscopes, consisted of two lines in the green, one quite the case of careful comparisons, and 10-3 per cent in the case of bright and the other saint.

The following formula is based upon On Tuesday, September 1 of this year, I again observed the the instantaneous ones. same phenomenon at Halifax, v.s. I was unable to make the careful comparisons, accurate observations, but noted the following facts :—The

A® -a luminous arch was quite bright when first observed, at 11.30

L = 1{1+

74 p.m., and extended from horizon to horizon. Fisteen minutes later it had completely faded away. It was about 4 or 5' in where l and L are the lengths (in degrees) of apparently equal width throughout its whole length. It met the horizon at arcs at a°, the lower altitude, and at A°, the higher altitude, repoints about 10° or 15o to the north of the east and west points, spectively; According to this formula, an arc 26" 48 long appears and passed through a point a few degrees south of the zenith the same length at whatever altitude it is situated, but an arc When first observed, it was approximately uniformly bright shorter than 26°°48 appears longer at the horizon than at throughout, except at the edges, where its brightness diminished the zenith, and an arc in excess of 26°:48 would actually appear rapidly outwards. To the eye its light seemed to be white, and longer near the zenith than near the horizon : an arc í 4 long stars were visible through it. In fading away, the east and west (the shortest in my observations), when at the horizon, would ends disappeared first, and the main body of the arch became appear equal to an arc in the zenith 109.85 per cent, of its gradually fainter, wider, and more variable in width. The night length; while an arc 100" (about the longest in my observations) was bright and clear, and the temperature lower than it usually at the horizon would appear equal to an arc of 71' 30 only in the is in the beginning of September, and there was no appearance zenith i.e. with its middle point in the zenith). When the of aurora in other parts of the sky.

above formula is applied to all the observations, the average Except on this occasion I have neither observed this pheno deviation of the observed lengths from the computed, is reduced medon nor heard of its occurrence since 1883. But as it might, to 4*2 per cent. in the case of the careful comparisons, and 7'0 readily occur without my either seeing it or hearing of it, I cannot per cent in the case of the instantaneous ones. If this formula say that I know it to be rare.

J. G. MACGREGOR. can rightly be applied to objects of such small dimensions as the Dalhousie College, Halifax, N.S., October 14.

sun and moon, it as will be seen, allows only a small increase for their apparent size near the horizon upon that when they are

seen at a considerable altitude, It has twice been my good fortune to observe phenomena It would be easy to find a more complex formula which would similar to that describe in NATURE of September 24 vol. satisfy the observations still better, bat these are not sufficiently xlit. p. 494). My recollections of the first occasion are some. numerous to warrant the doing so.

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