As regards the other matter referred to, Mr. Tittmann does not mention the publication in which "Mr. Chaney states that the standard air to which his result is reduced weighs 0.3077 grains per cubic inch." The only publication known to me is Mr. Chaney's paper in the Proceedings of the Royal Society, and it does not contain any such statement. I have always been taught to regard a standard weight as a standard of mass, and therefore independent of such conditions as temperature, pressure, and the material in the other scale pan; whereas, it appears that Mr. Chaney, by direction of the Board of Trade, has made a determination which is only true for a particular density of the surrounding air, and a particular density of the weights in the other pan. For scientific purposes a standard of reference should be free from variable elements, and should be of the utmost attainable simplicity. For commercial purposes determinations to six figures are frivolous. Mr. Tittmann's reductions appear to contain two errors. Instead of adding the weight of a cubic inch of air, he ought to have added the difference between this and the weight of the air displaced by the weights in the opposite pan. Again, he takes the metre as 39 3700 inches, whereas Clarke's value is 39'370432, and Kater's 39'37079. I have had some correspondence with Mr. Chaney since the publication of my new edition, and have had an erratum slip printed, which I trust you will allow me to subjoin, as it may be useful to several of your readers J. D. EVERETT. 5 Princess Gardens, Belfast, March 28. Addenda and Corrigenda. Page 63. In reducing Cailletet's experiments, should have been added instead of '000 0039. '0000026 Page 77. Add-Violle's determination of velocity of sound is 331 10 o'I. Ann. de Chim. XIX. March, 1890. Page 176, line 10. For Wuilleumeier, 1890, read Wuilleumier, 1890, Lippmann method. At end of page 164, add-Expressing C in amperes, R in ohms, and 7 in seconds, the heating effect in gramme-degrees is C2RT/4 2 24C RT. Page 35. Mr. Chaney's determination here quoted was not intended as a determination of the density of water, but of the apparent weight of water when weighed in air of density 001 21684 against brass weights of density 8'143. The correcting factor for deducing the weight in vacuo or true density is 1001 0687, which will change the value 998 752 obtained in the text into 999 82, to compare with Tralles' '999 88. Mr. Chaney's result is for distilled water deprived of air, and Tralles' appears to be for ordinary distilled water. According to results recently obtained by the Vienna Standards Commission (Wied. Ann., 1891, Part 9, p. 171), water deprived of air has the greater density, the difference being 000 0032 at 0° C., and 000 0017 at 62° F. These differences are too small to affect the above comparison. Influenza in America. In my copy of "Johnson's Dictionary of the English Language in Miniature, to which are added an alphabetical account of the heathen deities and a copious chronological table of remarkable events, discoveries, and inventions, by the Rev. Joseph Hamilton, M.A., second American edition, Boston, 1806" (12mo, pp. 276), I find on p. 275, "Influenza in North America, 1647, 1655, 1697-98, 1732, 1737, 1747, 1756-57, 1761, 1772, 1781, 1789-90, 1802." It is quite possible that these dates are well known, but they are new to me, and may be of interest in connection with the recent epidemic. EDWARD S. HOLDEN. Mount Hamilton, March 29. DUST COUNTING ON BEN NEVIS. meteorological problems which deal with clouds and precipitation, solar and terrestrial radiation, and in a general way with the diurnal and annual variations in the temperature and pressure of the atmosphere. Mr. Aitken's work in originating this branch of science, and in making and discussing numerous observations of the number of dust particles in the air of various places in this country, as well as on the Continent, at various altitudes, is pretty well known already (see NATURE, vol. xli. p. 394). Mr. Aitken's results and conclusions were looked upon as being of such importance as to warrant some of our leading meteorologists to apply to the Research Fund of the Royal Society for a grant to enable them to equip the Ben Nevis Observatory with Aitken's dust-counting apparatus. The application was successful, and instruments were at once ordered, and in due time erected at the Observatory. The The apparatus consists of two dust counters, one a portable form for use in the open air, and the other a laboratory form for use inside the Observatory. latter is fixed in the middle room of the tower, and has pipes leading out to the free air, so that it is possible to observe with it in almost all sorts of weather and at any hour day or night. The principle on which these instruments are constructed, so as to make the tiny invisible particles of dust visible and easily countable, is pretty well known already. Briefly it is this. To make the particles visible, the air containing them is saturated with water vapour, and by a stroke of an air-pump it is thereafter cooled so much as to cause a condensation of the vapour on the particles, whereby these are thus made visible. Ordinary air is so dusty that if the receiver were full of such air it would be impossible to count the particles, and to make them easily countable the following process is resorted to. First, the chamber or receiver, whose capacity is accurately known, is filled with pure dustless air by means of an air-pump and filter. Then a fifth, a tenth, or any other fractional part of the amount of pure air inside is taken out, and the same amount of dusty air allowed in. In this way the density of the shower caused by condensation is completely under the observer's control. A small graduated stage is placed one centimetre from the top of the receiver, so that all the dust above this falls on to it, and by means of a magnifying glass all the particles on one or more of the small squares of the stage are easily counted. Then, by multiplying by the reciprocals of the various fractions used we arrive at the number of dust particles in a unit of the free dusty air. In making an observation, the mean of ten such tests is taken as the number of particles present for that time. Observations were begun at the Ben Nevis Observatory with the portable instrument in February 1890, and with the other instrument in the following summer. During the whole of that year the work done was mainly preliminary, as great difficulty was experienced in getting the dust work to fit into the general routine of Observatory work. The dust inquiry is not like some other special inquiries, that can be prosecuted for a certain time, and then discontinued after definite positive or negative conclusions thereanent have been arrived at, but must, on the other hand, be carried on side by side with the other observations of meteorological phenomena, as pressure, temperature, humidity, &c., with any of which it is of equal importance, and having once been admitted into the general routine of meteorological observations it WITHIN the last few years quite a new factor has must be kept on. This fact was soon seen on Ben Nevis been introduced into the study of meteorologynamely, that which treats of the dust particles in the atmosphere, of the number of dust particles present in the air at any time, and the effect of dust in the air on climate and weather changes. It is now beginning to be recognized that the study of dust and its behaviour in the air forms the stepping stone to the study of almost all from the extraordinary variations that were observed in the dustiness of the air with changes of weather; and it was attempted to make continuous hourly observations of the dust as of the other elements. It was found, however, that this could not be done without crippling the general routine, this being as much as the two observers at the Observatory could well cope with. In February 1891 a system of three hourly observations of the dust particles was started, and this has been kept up with but few interruptions since. The dust observation is made immediately after the usual hourly set is completed, and it can thus be studied along with all the other hourly records in their relation to the prevailing weather. A great many observations have in this way been accumulated during the past two years, but we have not had time for studying them in detail yet. A mere inspection, however, brings out some interesting points. One of these is the enormous variation that is observed in the number of dust particles, not only in the course of the year, but often in the course of a few hours. At sea-level the number of dust particles in the air at any time depends very much on the locality and on the wind, whether blowing from a polluted district or not. The mean of a number of observations made by Mr. Aitken at Kingairloch, in the west of Scotland, is 1600 particles per cubic centimetre. In London, on the other hand, he found 100,000 per cubic centimetre, and in Paris rather more. On Ben Nevis the mean is 696 per cubic centimetre, the maximum being 14,400 per cubic centimetre, and on several occasions the minimum fell to o. A general mean does not convey a fair idea of the dustiness of the air at the mountain-top, although it may do so for places at sea-level, because there is at the former place a great daily range in the number of dust particles, depending on the rise and fall of the air past the place of observation. If there is any marked variation at sea-level it is entirely of a different character. Below are the means, as well as the maxima and mimima, of all the months that have a fairly representative number of observations. Number of Dust Particles per cubic centimetre on Ben Nevis. The above table shows that the Ben Nevis air contains most dust in spring, and it is probable that sea-level air is in this respect similar; the cause of this greater amount of dust in spring than at any other time of the year being the great annual westward motion of the whole atmosphere, or at least of a considerable depth of it, at that time of the year. In a recent paper on The Winds of Ben Nevis" (Trans. R.S.E., vol. xxxvi. p. 537), it has been shown that this is one of the very few points in which the high- and low-level winds agree, viz. in the excess of easterly winds in spring. The above means for summer are probably too low, as that summer was exceptionally cold, and the general circulation was very abnormal, and that in the direction which would tend to give low dust values. The maximum, 14,400, was observed at I p.m. on April 11, 1891; and, as an instance of how very much the values change in a short time, at 8 a.m. that morning the number was only 350 per cubic centimetre, and by midnight it had again fallen to 600 per cubic centimetre. The daily variation is fairly well indicated from the three-hourly observations. For the months of March, April, and May, 1891, the following are the means for the eight hours of observation : Here there is a minimum indicated (526) at 4 a.m., and a maximum (1438) at 4 p.m. All the forenoon values are below the mean, and the evening values above it. It would appear that during the forenoon the summit of Ben Nevis is above the first or lowest cloud or dust stratum. About noon this stratum rises to the level of the summit, and during the afternoon hovers above it, and falls again late at night. From this it might be inferred that the summit is oftener clear of cloud in the early morning, and oftener enveloped in the afternoon. A table showing the number of times the top was clear during the last seven years shows that only about 30 per cent. is clear weather in which the summit is free from fog; but it does not show a daily variation as indicated by the dust values, what little it does show being quite the reverse-namely, a maximum of clear weather in the middle of the day and a minimum at night. This clearly indicates that when the dust layer falls below the summit at night, radiation at once forms an independent cap on the hill-top; and again in the afternoon, although the dust stratum envelopes the summit, the opposite radiation warms it up and prevents condensation, or rather evaporates the watery particles of the cloud. So that, contrary to public opinion, the best time to visit the summit for the sake of the "view" is the middle of the day, and not the early morning. During fine settled weather the rise and fall of this cloud stratum can be followed, but in average weather the effect of radiation completely masks it. The effect of solar radiation and nocturnal radiation on dust, as particles and as strata, is a problem that has to be studied and worked out. Very little is definitely known about it at present. In the study of the nature and motions of clouds the dust observations will be of great value. When a fog envelopes the summit, the number of dust particles observed may vary greatly without any apparent change in the thickness of the fog, but as a rule dry thick fog contains a great amount of dust, while thin wet mist contains very little. It is when a thin drizzling mist envelopes the summit that the lowest values are always obtained, and then there is a distinct difference between the conditions at sea-level and those at the summit, the winds at the latter place differing in direction by 90° or more from the winds below, and sometimes the upper winds are blowing straight out from the centre of a shallow low-pressure area, and the dust that rises with the slight ascending currents of the lower strata is almost entirely filtered out before reaching a height of 4400 feet. One of Mr. Aitken's conclusions may briefly be put as follows: Much wind, little dust; much dust, little wind. That dust seems to accumulate in the quietest places is fully borne out by the Ben Nevis observations. This is true not only horizontally, but also vertically, and it seems probable that this is what chiefly determines the position of cloud strata at all heights. And from this we may infer that the motion of clouds is much slower than that of the general aërial currents; and again, since clouds tend to form between currents, and may have as direction of motion the resultant of the directions of these currents, it follows that as indices to the motions of the upper air the velocity and motion of clouds are very unsatisfactory. Observations of the apparent haziness of the atmosphere are made whenever it is possible, and the relations between the haziness of the air, the humidity, and the number of dust particles, have been found to be the same as what Mr. Aitken pointed out. Briefly, he found that with a constant humidity the haziness increased or diminished with the number of dust particles, and with a constant number of dust particles the haziness depended on the humidity (at least when the air was within 10 or 15 per cent. of saturation); for with increase of humidity the air became thicker, because apparently condensation begins on the dust particles before the air reaches its point of saturation. The dust observations promise to be of special value in the study of weather types. In some weather types, not only are the dust values very abnormal, but the daily variation is in some instances quite abnormal also, indicating that the cloud or dust strata are differently situated from what they are in average weather, and also that their daily rise and fall occur at different times. In March 1890, the dust values show this very well below are the three-hourly means for each of three different periods : Hour Number per cubic centimetre.. First Period (12 days). Prof. Judd, who has kindly sent me a copy, I extract the following: Pantelleria, an island (135 by 8 kilometres), situated between Sicily and Tunis, is entirely of volcanic origin.' The volcanic activity would at present appear to be a shade less marked than in the "Phlegræan Fields," west of Naples. In Pantelleria we have exhalations of CO; hot springs (of which those at the lake called "Bagno del Acqua," among other things are, we are told, so rich in alkalies as to lather, and be used for washing clothes !), and fumaroles, some of which exhale steam harmless to vegetation, and with little if any specific effect on the rocks, while others give out sulphurous vapours at 88° C. or more, 102 decomposing the rocks about them. 22 Second Period (3 days). 65 25 37 19 20 28 93 76 During the third period of five days the weather was very remarkable. A large depression was slowly progressing eastwards to the north of Scotland, and the winds on Ben Nevis were blowing almost straight out from the centre, while the winds at sea-level were circulating in the normal direction. This is the usual type when low dust values are obtained; but it is difficult to quite account for the daily variation in the dust values being reversed, the higher values occurring at night, and the lower in the middle of the day. This and many other points have not been studied yet. Dr. Buchan, in his recently published work on "Atmospheric Circulation," hinges his explanations of various atmospheric phenomena on the effect of solar and nocturnal radiation on the dust in the atmosphere, and accounts it one of the most important factors in the study There is but doubtful record of seismic disturbances in earthquakes occurred, with elevation of part of the north the island prior to the summer of 1890. Then, however, coast, the cracking of cisterns, and an increase in the number and activity of the fumaroles, so that vineyards formed in some of the old craters were damaged. After more than a year's interval, earthquakes again commenced October 14, 1891 (three days before the eruption). These were accompanied by drying up of certain springs, and apparently a further rise on the north coast, with surface cracks in that district. As the shocks were most violent and vertical at the little town of Pantelleria itself (at the end of the island nearest the scene of eruption), they caused considerable consternation; and if one went by the account of the overstrung inhabitants, who felt shocks not recognized by the seismoscopes, one might exaggerate their violence. On the other hand, the walls of the houses, which outside the town have frequently no upper story, are, on the whole, substantially built, so that the insignificant damage (Fig. 1) appears to have been raised, in the two years, done is perhaps hardly a gauge. Part of the north coast ABSTRACT OF MR. A. RICCO'S ACCOUNT OF OF what happens in submarine eruptions we naturally Mr. A. Ricco has recently published a detailed and illustrated account of the facts he was able to gather, concerning last October's submarine eruption north-west of Pantelleria, either in person or from local and other observers, he having reached the island during the latter part of the eruption. From this, at the suggestion of 1 Annali dell' Ufficio centrale Meteorologico e Geodinamico, ser. ii., Parte 3, vol. xi. 2(a) Lyell's "Principles of Geology"; and (b), for Bibliography, Johnston-Lavis's "South Italian Volcanoes," pp. 105-107., 3(a) South Italian Volcanoes," pp. 64 and 65; and (b) Giov. Platania, "I Fenomeni Sottomarini durante l'Eruzione di Vulcano (Eolie) nel 18881889," Att. Rend. Acc. Sc. Let. Art. Acireale, n. ser., vol. i., 1889, pp. 16, tables 3. FIG. 1.-Map of Pantelleria, showing the position, according to Ricco, of (a) the submarine eruption of October 1891, and (, ) of the raised coast. some 80 cm., the old sea-level being marked by a line of white incrustations; and we are told that, according to a recent estimate,2 the tide in this part of the Mediterranean has an amplitude of but some 8 cm. ; besides, there was the evidence of inhabitants who had bathed, boated, and fished along the coast. The submarine eruption (4 kilometres north-west of the island, Fig. 1) began on October 17, 1891, when the earthquakes abated, and water returned to some of the wells. The appearance of the sea, as viewed from the land, at first suggested the presence of some "great fish," and columns of "smoke" were seen. Those who visited the spot later (Fig. 2) found black Europe, and an exorbitant price is naturally asked for it. In South Africa the Giraffe is practically extinct, being only still met with in a few isolated localities nearly a thousand miles from Cape Town. In East Africa there are still Giraffes, and in places nearer the sea-board; but here, apparently, there are no means of catching them alive, as the natives do not understand how to do it. Here, however, it is that there appears to be most like lihood of obtaining a fresh supply. This will be an expensive business, but unless some steps are soon taken in the matter it seems that the younger generation of England will grow up without knowing what a living Giraffe is like. Their parents have been more fortunate. From the list given below, it will be seen that there have been 30 individuals of the Giraffe exhibited in the Zoological Society's Gardens since 1836, of which 17 have been born there, and 13 acquired by purchase. Of these 30, one was presented to the Royal Zoological Society of Ireland in 1844, five have been sold at prices varying from £450 to £150, and the remainder have died in the Gardens. No. | Sex. List of Giraffes that have lived in the Society's Gardens. How obtained. FIG. 2.-Part of a sketch of the submarine eruption near Pantelleria, 4 8 Do. 58 Born in the Menagerie, June 19, scoriaceous bombs rising to the surface, along a line I should add, in conclusion, that I have ascertained from Dr. Errera, who has charge of the seismological apparatus on the island, that the telegrams published in an English daily paper, as to renewed eruptions in the neighbourhood at a later date, were quite without foundaG. W. BUTLER. tion. March 22. 28 3:61 Do. 29, 1846. Do. Jan. 14, 1849. do. Jan. 6, 1837. June 28, 1839. 1839. 7.8 Do. do. 88 Do. do. Feb. 25, 1844. Presented to the Dublin THE NOTES. THE ordinary general meeting of the Institution of Mechanical Engineers will be held on Thursday evening, May 5, and Friday evening, May 6, at 25 Great George Street, Westminster The chair will be taken at half-past seven p. m. on each evening, by the President, Dr. William Anderson, F. R. S. The President will deliver his inaugural address on Thursday evening, after which the following papers will be read and discussed, as far as time permits :-Research Committee on Marine-Engine Trials : Report upon trial of the steamer Ville de Douvres, by Prof. Alexander E. W. Kennedy, F.R. S., Chairman (Thursday, and discussion continued on Friday). On condensation in steam engine cylinders during admission, by Lieut. -Colonel Thomas English, of Jarrow (Friday). The anniversary dinner will take place on Wednesday evening, May 4. THE Royal Academy of Sciences of Lisbon has elected Sir Joseph Fayrer, F. R.S., as a foreign corresponding member in the class of mathematical, physical, and natural sciences. DR. R. THORNE THORNE, F.R.S., as was expected, has been appointed principal Medical Officer of the Local Government Board, in succession to Sir George Buchanan, F.R.S. WE regret to have to record the death of Miss Amelia B. Edwards. She died on Friday last at Weston-super-Mare. Miss Edwards had done much both in England and in America to awaken public interest in the results of archæological research in Egypt. She also did excellent service by her work in connection with the organization and control of the Egypt Exploration Fund. MR. J. CARRUTHERS, son of Mr. W. Carruthers, head of the Botanical Department of the British Museum, has been appointed Lecturer in Botany at the College of Agriculture, Downton, for the coming summer. Mr. J. Carruthers has for some time been Demonstrator in Botany at the Royal Veterinary College, London. AN International Economic Congress will be held at Antwerp in August next. MR. W. CLAYTON PICKERSGILL, H. B. M. Vice-Consul at Antananarivo, who has just returned to England on leave, has brought with him a nearly perfect egg of the extinct gigantic Bird of Madagascar, pyornis maximus. This was obtained, like all other previous specimens, from the southern coast of the island, near Cape Ste. Marie. Mr. Sclater will exhibit the egg at the next meeting of the Zoological Society, on May 3. ALL collections of plants received at the Royal Gardens, Kew, are examined, and reports upon them are sent to the donors. When of sufficient magnitude and importance, they are made, as in the case of the late Colonel Grant's collections in Central Africa, the subject of a detailed memoir. Anything of sufficient interest in smaller collections is illustrated with a plate in 'Hooker's Icones Plantarum." Novelties which are not important enough to justify a plate have hitherto been relegated to their proper places in the Herbarium, where they have awaited description by some monographer. Collectors, however, are best encouraged when they see that the result of their labours supplies some tangible addition to scientific knowledge; so it has been decided that all plants received at Kew of which the novelty can be ascertained with some certainty shall be described for the information of botanists, and distinguished by formal names. Successive decades of plant-descriptions are to be published in the Kew Bulletin. The first decade appears in the April number, and suffices to indicate that the series will be one of great interest and value. BESIDES the first of the "Decades Kewenses," the April number of the Kew Bulletin contains sections on Fiji ginger, the agricultural resources of Zanzibar, and the botanical station, St. Vincent. WE learn from the Kew Bulletin that among the botanical treasures which have lately reached the Royal Gardens, is a second small collection of dried plants, sent by the Rev. R. B. Comins from the Solomon Islands. It includes several highly interesting things. Specially interesting among these are flowering specimens, though not perfect, of the tree that bears the so-called turtle-seeds of the islanders. This tree belongs to the Sapotacea, and will shortly be published as a new genus of that order by Mr. W. B. Hemsley. The seeds are one of the most singular productions in the vegetable kingdom, and the name given to them by the natives of the Solomon Islands is quite appropriate, as the resemblance is most striking. Mr. Comins collected seeds of what appears to be a second species of the genus, and Kew previously possessed a seed and foliage of a third species, collected in the Fiji Islands in 1878 by Mr. Horne, the Director of the Botanic Garden of Mauritius. There are also seeds of one or two other species in the Museum, where they have been for some years, but their origin is unknown. The Bulletin also calls attention to another very curious plant collected by Mr. Comins-Lasianthera papuana-in which the originally three-celled ovary develops into a fruit with one fertile, dry, woody cell, the two empty cells forming a fleshy body on one side of it. IT is expected that the Borough Road Polytechnic Institute will be opened in October next. When the ceremony has taken place, two of the three Polytechnics for South London, for which Mr. Evan Spicer and his committee first appealed in 1888, will be at work. The Goldsmiths' Company's Institute at New Cross, which by the munificence of that Company was opened in October last, has considerably over 4000 members on its books. The third Polytechnic, that at Battersea, is in a fair way towards completion, and will, it is hoped, be opened in October 1893. PROF. T. G. BONNEY, F. R.S., will on Tuesday next, April 26, begin a course of two lectures at the Royal Institution, on "The Sculpturing of Britain: its later stages"; and on Thursday, April 28, Prof. Dewar, F.R.S., will begin a course of four lectures on "The Chemistry of Gases." The Friday evening meetings will be resumed on April 29, when Dr. Benjamin W. Richardson will deliver a discourse on "The Physiology of Dreams." Mr. Alfred W. BENNETT will deliver a course of lectures on systematic botany at the Medical School, St. Thomas's Hospital, on Tuesday and Wednesday mornings at 10 a.m., beginning Tuesday, May 3. DR. SYMES THOMPSON will deliver at Gresham College, on April 26, 27, 28, and 29, a course of lectures on "The Eye in Health and Disease." The lectures are to be illustrated by diagrams, and will begin each evening at six o'clock. ACCORDING to a Reuter's telegram, despatched from New York on Monday, two severe shocks of earthquake were felt at Portland, Oregon, at two o'clock on Sunday afternoon, and at various places in the vicinity. Numbers of buildings trembled, and so great was the alarm that people rushed panic-striken into the streets. The vibrations were from west to east, lasting ten seconds in each case. No damage was done, and as the seismic disturbances were confined to two sharp shocks within a brief interval of each other, a feeling of confidence gradually returned. SNOWSTORMS of exceptional severity have passed over the country during the last week, and in many parts of the kingdom the fall was heavier than at any time during the past winter. In Scotland, and over the northern parts of England, snow had been falling heavily on several days, and on Good Friday a shallow cyclonic storm area was approaching our south-west coasts from off the Atlantic, which occasioned heavy snowstorms in the Channel Islands and south-west of England. The central area of this disturbance passed up the English Channel and over the north of France, accompanied by an unusually heavy fall of snow over the south and south-east of England. The ground was covered in places to the depth of several inches, and the storm caused considerable damage to the telegraph wires in the southern parts of the kingdom. The night frosts were also very severe, the shade thermometer registering as low as 20° in places. THE Report of the Kew Committee of the Royal Society for fourteen months ending December 31 last gives an account of |