surface is more nearly black than white, which seems to render the existence of snow fields upon it less probable, unless they are covered with volcanic dust, as the end of a glacier usually is with rock débris. But even if we take Mr. Reade's view, it is still conceivable that steam may have been the explosive agent in the moon's volcanoes, while her internal temperature was very high, and that the resulting water may have been subsequently absorbed after the body became cool, because the water would occupy less space within the interstices, which this theory of imbibition postulates, than the equivalent vapour did, when the temperature was high. The case of the earth would not be a parallel one, because it has not yet cooled. Although not myself a selenologist, I have a suspicion that very little is known about the constitution of the moon; and that it is not even certain that its enormous craters are all of them really volcanic. It has been admitted by Prof. Darwin, in discussing the subject with Mr. Nolan, that on his view of the genesis of the moon it must have originally existed as a "flock of meteorites." These falling in during the later stages of the building up of its mass would have produced pits on a viscous surface, much like some of the craters. At any rate it seems unsafe to rely upon arguments respecting the condition of the earth's interior, of which we know little, drawn from that of the moon's body, of which we know less. Harlton, Cambridge. O. FISHER. Exact Thermometry. THE interesting experiments of Dr. Sydney Young, recorded in NATURE of December 19 (p. 152), seem to leave no doubt that the main part of the permanent ascent of the zero-point of a mecurial thermometer, after prolonged heating to a high temperature, is not due to compression of the bulb--rendered more plastic by the high temperature-by the external atmospheric pressure. Researches on the effects of stress on the physical properties of matter have convinced me that the molecules, not only of glass, but of all solids which have been heated to a temperature at all near their melting-point, are, immediately after cooling, in a state of constraint, and that this state can be more or less abolished by repeatedly heating the solid to a temperature not exceeding a certain limit, and then allowing it to cool again (it is not only the heating but the cooling also that is efficacious). It appears that the shifting backwards and forwards of the molecules, produced by this treatment, enables them to settle more readily into positions in which the elasticity is greatest and the potential energy is least. This "accommodation" of the molecules, as Prof. G. Wiedemann and others have called it, is, as one might suppose, attended with alterations of the dimensions and other physical properties of solids, and is not confined to the release of molecular strain set up by thermal stress, but is extended to the strain set up by any stress whatever. As years roll on, the time of vibration of a metal pendulum gradually alters (and so, no doubt, do the lengths of our standard measures), the bulb of a thermometer diminishes in volume, a steel magnet parts with more or less of its magnetism, a coil of German-silver wire gains in electrical conductivity, &c. The changes in all these cases would probably be far less than they actually are if the temperature throughout the whole time could be maintained constant ; but this last is not the case-heating and cooling goes on more or less every day. We may assist the effect of time by artificially increasing the range of temperature, but it would appear that we must not exceed a certain limit of temperature, which limit depends partly upon the nature of the substance and partly upon the stresses that are acting upon it at the time. Thus, the internal friction of a torsionally oscillating iron wire which has been previously well annealed may be enormously diminished by repeatedly raising the temperature to 100 C., keeping it there for several hours, and then allowing it to fall again. The amount of diminution of internal friction depends upon the nature of the wire, and on the load which there is at the end of it (if the load exceeds a certain amount, the friction is increased instead of diminished). In attempting to "accommodate "the molecules in this manner the heating must, at any rate in some cases, be prolonged for several hours, and the substance should then be allowed to remain cold for a still longer period. I have not had much experience with glass, but I think it prob able that the settling down of the zero-point of an ordinary thermometer into its ultimate position could be very materially facilitated by the heating and cooling process mentioned above. HERBERT TOMLINSON. 36 Burghley Road, Highgate Road, December 23, 1889. Self-luminous Clouds. WITHOUT venturing to call in question the occasional occurrence of self-luminous clouds, I may be permitted to relate an observation which seems to reveal a possible source of error in the records of such phenomena. On June 14, 1887, about 10.45 p.m., I witnessed an appearance over the north-north-west horizon which struck me as very remarkable. Amidst the strong glow of twilight a few fragments of cirrus cloud shone with a pure white light having so much the character of phosphorescence that it was difficult to believe the objects were not self-luminous. Looking out again an hour later, I found no trace of bright clouds, but in their place were small bands of cirrus showing dark and grey against the feeble twilight that remained. I could not but conclude that the clouds in both instances were the same or similar, lit up by the direct rays of the sun at the time of the first observation, and having lost his rays at the time of the second observation. Had they been self-luminous they should have become brighter instead of darker as the twilight faded. It has been suggested to me that the bright clouds seen at 10.45 p.m. may have owed their brightness, not to the sun's rays falling on them at the time, but to a temporary phosphorescence, the result of exposure to the sun's rays in the day-time, and that this temporary quality had died out in the interval between the two observations. I think this explanation is unnecessary for the following reasons. In the first place, it is certain that if a cirrus cloud were present in the atmosphere at a sufficient height to catch the sun's rays at 10.45 p.m. of a midsummer day, it would appear as a bright object amidst the surrounding gloom. And, secondly, there can be nothing incredible in the presence of a cirrus cloud at that height, when the persistence of twilight proves the presence of atmospheric particles of some kind at a greater elevation Clifton, December 19, 1889. still. GEORGE F. BURDER. Duchayla's Proof. I HAVE read with much interest the new proof given by Mr. W. E. Johnson of "the parallelogram of forces," in NATURE of December 19 (p. 153), and regard it as deserving a place among the best proofs that have been given. I think, however, that, in his criticism of Duchayla's proof, Mr. Johnson runs to excess, when he says, "To base the fundamental principle of the equilibrium of a particie upon the transmissibility of force, and thus to introduce the conception of a rigid body, is certainly the reverse of logical procedure." Duchayla's proof only requires us to suppose the transmission of force by strings. A particle is unthinkable. In presenting to a learner the conception of three equilibrating forces acting on a particle, we cannot do better than represent the forces by pulls in strings, and the particle itself by the knot where the three strings are tied together. All the steps of Duchayla's demonstration that the resultant force is directed along the diagonal of the parallelogram can be presented in tangible form with the aid of strings. I do not think this is an illogical or unnatural procedure. J. D. EVERETT. Belfast, December 23, 1889. The Satellite of Algol. THE results of Vogel's photographs as to the satellite of Algol are of great interest to your astronomical readers. The ob servations made at Greenwich tended to the same result, but were unfortunately intermitted before anything approaching certainty was arrived at. Regarding it as certain that the variations of Algol are due to the interposition of a satellite, the question of the slight change in its period and the much larger change observed in the period of another variable of the same class in Cygnus becomes important. Besides the possibility of a third disturbing body it may be remarked that the existence of the solar corona and perhaps other appendages of the sun suggests that a resisting medium may exist in the entire space traversed by Algol and its satellite at each revolution. Also if the influence of gravitation is propagated in time (with whatever degree of velocity) the very rapid angular motion of a satellite which performs a complete revolution in less than three days (and in another variable of this class in twenty hours) could hardly fail to exhibit traces of this time-propagation. The attractive force, in fact, would never act in the line joining the centres of the principal star and satellite, and the deviation would probably be perceptible. I hope some mathematical astronomer will take up the problem, and show what the effects of each of these supposed causes would be. W. H. S. MONCK. 16 Earlsfort Terrace, Dublin, December 21, 1889. Maltese Butterflies. IN reading Mr. Wallace's "Darwinism" I am reminded by his observations on Island fauna (p. 106) of the impressions made upon me by the natural productions of Malta. My time was so fully occupied that I had little opportunity of exploring the country districts. I paid one visit to the extraordinary ruins of a Phoenician temple at Hagiar Kim, and one to the curious islet in St. Paul's Bay. On the latter I noticed several strange thistles and a beautiful flower-something like a large pink or purplish Tutsan. On the barren wastes round Hagiar Kim many familiar wild flowers grew, but all seemed shrunk and shrivelled as compared with those of Britain. The only unfamiliar one was called by the natives "the English flower." It was a tall trefoil with a drooping yellow trumpet-flower (not at all papilionaceous in form), and grew plentifully by the edges of the dustiest roads-unlike anything I know in England. I lived for some time at the Imperial Hotel, at Sliema, which has a somewhat extensive garden, in which I used to spend about half an hour every morning. During April and May it was very lovely. The oleanders were then in their richest bloom; a shrub like a gigantic heliotrope, both in flower and leaf, was frequented by myriads of humming-bird moths; there were a few strawberry-plants, the fruit of which was delicious, although even smaller than that of our own wild kind; but most attractive to me were the clumps of valerian and scabious which were haunted, just as at home, by crowds of butterflies. These included blues, coppers, wood-ladies, painted-ladies, red-admirals, tortoise-shells, and swallow-tails. All of these were smaller than their English relatives are, and much less brilliant in colour. The swallow-tails were especially dwarfed in their proportions. I am puzzled to account for their presence in Malta, as there is nothing like a marsh or a fen in the whole island, whilst in England they are only to be found in the district of the meres. Can any of your readers throw light on this mystery? I saw several of the larger hawk-moths. They did not seem to suffer in size, but even they were dimmer in their colours. Hoping to get a general idea of Maltese entomology, I visited the University Museum-only to find a few cases of insects in which every specimen had been devoured by mites! GEORGE FRASER. Leighside, Tunbridge Wells, December 22, 1889. A Preservative. I HAVE been very much troubled in conducting classes in mammalian anatomy by the want of a preservative medium which would retain the natural colour and texture of tissues, would impart to them no offensive smell, would be inexpensive, and easily handled. Various experiments with freezing, alcoholic, glycerine, and other media have all proven failures, and this fall I turned to experimentation upon the simplest and cheapest of all chemical reagents-water and table-salt. My entire success with these was so satisfactory that I shall, at the risk of telling an old story, state the experiments here. I tried preserving squirrels in three strengths of salt solution, one of 5 parts by weight of salt to 95 of water, a second of 10 per cent. salt, and a third of 15 per cent. All gave satisfaction, but the 10 per cent. seems best, because the weakest solution in which putrefaction could not take place. Specimens placed in five times their bulk of this solution retain the natural flexibility of all the tissues; the peculiar look of nerve-tendon and blood-vessel against muscle is retained; the tint of muscle is faded somewhat by the solution of hæmoglobin from the blood, but it is still distinctly reddish; there is no putrefactive odour; all of this after four weeks standing in the laboratory. This is so simple a preservative that I wonder that it is not in common use. H. LESLIE OSBORN. Hamline University, St. Paul, Minnesota, The Evolution of Sex. IT is a fact well known to pigeon fanciers that the two eggs laid by pigeons almost invariably produce male and female. But no attempt appears to have been made to ascertain which of the two eggs produces the male, and which the female. The second egg is laid about twenty-four hours after the first. I have kept pigeons for seven or eight years, and have only met with one or two instances of the young birds, produced from the two eggs, being of the same sex. Recently I have made several experiwhich the eggs are laid and the sexes of the young birds ments to ascertain if any relation exists between the order in produced. The results show that the egg first laid produces the female, the second egg the male. It may, perhaps, be well to give the experiments. (i) Egg I of pair A produced a female; egg 2 was bad. (ii) Egg I of pair B produced a female; egg 2 a male. (iii) Egg I of pair B produced a female; egg 2 a male. (iv) Egg 2 of pair B produced a male; egg I was bad. (v) Egg I of pair C produced a female; egg 2 was bad. (vi) Egg 2 of pair D produced a male; egg I was broken. These experiments were made on white fantail shakers. large number of experiments must be made to prove if this relation does exist; should it be found correct, an examination of the eggs and of the ovary of the parent might throw some light upon the "evolution of sex." M. S. PEMBREY. Oxford, December 14, 1889. Fighting for the Belt. A A FIGHT has been going on in my verandah for the last halfhour between two young birds-minas-with four birds of last season looking on. 66 Now the fight is just over. I have watched it throughout, and am positive that one of the on-lookers walked often round the combatants without interfering; and that another on-looker came, when he (or she?) could, and attacked one of the fighters. I say came when he could," because the other on-looker prevented him if possible-even fighting to that end. It seemed to me very much as if two youngsters from different nests were fighting for the belt, and the parents looking on-the one complacently at her offspring's success, the other angry and breaking the rules of the ring to help the weaker. F. C. CONSTABLE. Karachi, December 1, 1889. The British Museum Reading-Room. THE proper ventilation of this spacious room is a problem, surely not insoluble, but still awaiting solution. Is it not a serious grievance that to make use of one of the finest libraries in existence, means, for many, injury to health? Bad headaches and other ills, due to the stuffy and impure atmosphere which collects about the desks, are a common experience; and I know men who have given up going to the place on that account. For readers who live by work which can only be done there (some of whom are women), the matter is especially grave. Officials, again, will tell you that they often feel thoroughly done out after their day's work, which in itself is not generally severe. It seems to me the atmosphere improves after the lamps are lit ; possibly owing to the upward current of heated air. If this were verified, it might offer a clue to improvement. The whole matter calls for thorough scientific investigation; and I would suggest, as a preliminary step, that analysis be made of the air (say) on a Saturday afternoon, with regard not only to its gaseous constituents, but also to micro-organisms, which are no doubt plentiful. A. B. M. IN "AMONG CANNIBALS." 1 N the year 1880, Mr. Carl Lumholtz-as he explains in the preface to the work the title of which is given below-undertook an expedition to Australia, partly at the expense of the University of Christiania, with the object of making collections for the zoological and zootomical museums of the University, and of instituting researches into the customs and anthropology of the Australian aborigines. His travels occupied four years, and the first part of that time he spent in the south-eastern colonies, South Australia, Victoria, and New South Wales. From November 1880 to August 1881 he was in Central Queensland, and at the latter date he began his first journey of discovery, in the course of which he penetrated about 800 miles in Western Queensland-the results, he says, in no wise corresponding to the hardships he had to endure. He then went to Northern Queensland, where he spent fourteen months in constant travel and study, his headquarters from August 1882 to July 1883 being in the valley of what he describes as "the short but comparatively broad and deep Herbert River," which flows into the Pacific at about 18° S. lat. From his base on this river he made expeditions in various directions, extending in some instances to nearly 100 miles, and he repeatedly came in contact with savages who had never before been visited by a white man. It is to the period spent by him in the camps of the northern aborigines that Mr. Lumholtz chiefly devotes attention in the present volume, and it would hardly be possible to praise too highly the manner in which he has recorded his experiences. In every part of his narrative he displays a remarkable power of keen and accurate observation, and he presents his facts in a style at once so fresh and so simple that from beginning to end the reader's interest is maintained. Hitherto students of anthropology in Australia have derived their materials mainly from the southern part of the continent. Mr. Lumholtz may almost be said, therefore, to have broken new ground, and it is ground which it was well worth while to break, for the northern aborigines-from an anthropological point of view-are even more interesting than the southern tribes. They are decidedly at an earlier stage of development, and many of them have been only slightly and indirectly influenced by the ideas of European settlers. If there are any survivors of the school of Rousseau, who attributed so many fine qualities to "the noble savage," it would be wholesome for them to study what Mr. Lumholtz has to tell about the savages of Northern Queensland. A more unlovely picture than his description of these poor people it would hardly be possible to imagine. He went to Australia full of sympathy with the natives; when he left it, he found that his interest in them was as deep as ever, but that his sympathy had nearly vanished. That they are cannibals is beyond doubt. Luckily, they do not take to white flesh; it has too salt a flavour for their taste. But native flesh, when they can get it, provides them with the meal they like best, and they are quite willing to talk freely about the parts which they consider the most delicious morsels. They are not only treacherous, but seem to have not the faintest idea that treachery is anything to be ashamed of. If anyone is kind to them, they at once mistake his motive they fancy that his generosity springs from fear, and if this notion gets into their minds, it is time for their benefactor to look about him, for they will not scruple to kill him in order to obtain possession of his goods. Mr. Lumholtz found that, when accompanied by a party of natives, it was unsafe for him to walk in front; he had always to bring up the rear, and to keep every one well in view. At night, before going to sleep in his tent, he had to fire his gun as a reminder that he had the means of defending himself. For this weapon they had the most profound respect; also for his revolver, "the baby of the gun." The supreme ambition of the native is to have as many wives as possible, their number being regarded as a test of his wealth and importance. And he takes good care that they shall not earn his approval too easily. All the hard, disagreeable work has to be done by women, and when they excite the displeasure of their lords they may think themselves well off if they are not severely beaten. In every way these savages are creatures of impulse. It is difficult for them to fix their attention on anything, and they can look ahead only a very short way. Fortunately for themselves, they have no intoxicating stimulants, but tobacco gives them intense delight, and it was chiefly by promising to reward them with small quantities of it that Mr. Lumholtz was able to secure their services. When they have a chance, they gorge themselves with food; and on a hot day they plunge like dogs into water they may happen to pass. At the approach of night they become timid, trembling at every sound they hear in the bush; but with sunrise all their fears are dispelled, and after they have become thoroughly awake-a rather slow process they are ready for any pleasure that may come in their way. It is a happy moment for them when they discover a tree in which there is honey. This they eat with rapture; and Mr. Lumholtz says he has known cases in which they have lived upon it for three days in succession. If a savage finds such a tree, and is not able at once to take possession of its treasure, he marks the tree, and the mark will be respected by members of his own family or clan. There is, however, no conception corM.A. With Maps, Coloured Plates, and 122 Illustrations. (London: John responding to the idea of property, so far as anything I 44 Among Cannibals: an Account of Four Years' Travel in Australia, and of Camp Life with the Aborigines of Queensland." By Carl Lumholtz, Murray, 1889.) We are indebted to the kindness of the publisher for the use of the cuts reproduced in this article. claimed by strangers is concerned. in which they spend their lives. They display extraordinary cleverness in climbing trees, and their sense of they have considerable skill. Fig. 1 represents a browband of native workmanship (size). This specimen however, comes from Central Queensland. The Australians are generally supposed to throw the spear well, but Mr. Lumholtz never discovered any remarkable ability of this sort among the blacks of Herbert River. Fig. 2, represents a wallaby hunt, which he had an opportunity of seeing. He says: "Soon those who had remained behind spread themselves out, set fire to the grass simultaneously at different points, and then quickly joined the rest. The dry grass rapidly blazed up, tongues of fire licked the air, dense a young cassowary, which the natives one day brought to him, with two eggs. He at once asked the natives to guide him to the nest, near which, in a bed of loose leaves, he placed the young bird, hoping to attract the old one. After the lapse of about ten minutes they suddenly heard the voice of the cassowary. This usually sounds like thunder, "but now, when calling its young, it reminded us of the lowing of a cow to its calf." Soon the beautiful blue and red neck of the bird became visible IT BRITISH EARTHQUAKES. T is somewhat remarkable that the ordinary notion that Great Britain has a special immunity from serious earthquake phenomena, still very generally obtains credit. An explanation of this popular fallacy may perhaps be found in the simple fact that, on the average, few people living at any one time chance to have experienced any considerable shock; whilst in the case of those few-we except the many who were affected by the disastrous Essex earthquake five years ago-who have felt the sensation, as a momentary mental impression it has been soon for among the trees. The creature" stopped and scanned its surroundings carefully in the dense scrub, but a charge of No. 3 shot, fired from a distance of fifteen paces, laid it low." Six natives carried home the prize, which proved to be an unusually fine specimen of a male. We cordially recommend this book to all who take an interest in anthropology and zoology, or in incidents of travel through unfamilar scenes. They will find in it much that cannot fail to give them genuine pleasure. gotten. It should, however, by this time be more generally known and accepted that no part of the habitable globe is entirely exempt from seismic action, and that earth-tremors of considerable amplitude and intensity are by no means necessarily connected with volcanic disturbances, as was formerly supposed. When it is duly recognized that, at the lowest computation, 600 disconnected shocks are known to have taken place in this country during the present era, the popular belief respecting" our tight little island" may well be entirely shaken. This number includes many earthquakes of considerable magnitude, and the additional seismological |