marriage, and continuing to do so in successive gener-pological. There seems to be nothing against Aristotle's view that the tribe grew out of the family, except the curious but fashionable prejudice in favour of an organisation for primitive man of the baboon type. Mr. Atkinson in a remarkable paper has dealt the latest and one of the shrewdest blows at this prejudice, and doubtless anthropologists may in time revert to Darwin's suggestion that the earliest form of the human family resembled rather that of the unsocial anthropoids, such as the gorilla. It is noteworthy that Dr. Howitt modifies considerably the earlier conception of the Undivided Commune, and regards it as having been originally something like "what occurs when the modified Communes of the Lake Eyre tribes reunite." The battleground of the two schools is, of FIG. 2.-The Bret or Dead Hand. From Howitt's "The Native Tribes of course, the so-called group-marriage of the tribes last Noticeable details are that the action of jealousy is very strong in the Dieri tribe; that, as the Rev. O. Siebert puts it, "the practice of Pirrauru is worthy of praise for its strength and earnestness in regard to morality, and in the ceremonial with which it is regulated, since no practice could be less in accord with the hetairism which Lord Avebury has imagined for the Australian aborigines" (p. 186). It is disappointing to find that no mention is made of Cunow's theory of the four and eight subclasses; it would have been instructive to see what light an unrivalled personal knowledge of the system and an acquaintance, doubtless extensive, with the dialects might have thrown on the view that these classes are age-divisions, and have primarily nothing to do with marriage-restrictions. The Kurnai with their totems which do not affect marriage, and their local, not classdivisions, present a fascinating problem, and no one knows more about the Kurnai than does Dr. Howitt. Their marriage by elopement, and the systematic use therein of priestly assistance, are remarkable customs. "It was the business of the Bunjil-yenjin to aid the elopement of young couples. For instance, when a young man wanted a wife, and had fixed his mind on some girl, whom he could not obtain from her parents, he must either go without her, persuade her to run off with him, or call in the aid of the Bunjilyenjin. In the latter case his services were retained by presents of weapons, skin-rugs, or other articles." The Bunjil-yenjin then sang a magic song until he thought his magic strong enough to secure the "covering up" of the parents in a state of coma. The author in a very interesting essay applies the facts of "maternal descent" to the Teutonic Salic Laws. Among the more important features of the book is the masterly and final settlement of the vexed questions of the native headmen, and the belief in supreme beings, like Daramulun. The connection between the two questions is that the headman in the sky is the analogue of the headman of the tribe on the earth. Among the Kurnai-to note another difference between many of the south-eastern tribes and those studied by Spencer and Gillen-the knowledge of Mungan-ngaua is confined to the initiated men, who impart it in all sincerity to their novices; the Arunta, as Spencer and Gillen inform us, take this opportunity of explaining their deity away as a being only believed in by women and children. Among further details of interest are the Kurnai custom of the Dead Hand, the performance of the Indian Rope Trick by Kurnai medicine-men, the magical influence which exists between opposite sexes, and the belief that the initiated elders infuse their own magical power into boys at confirmation. The book is a fitting crown to Dr. Howitt's labours, and is, in effect, the most considerable and important of all studies of the Australian race. A. ERNEST CRAWLEY. CHANGES UPON THE MOON'S SURFACE. UNTIL within the last few years there has been a very general opinion that the moon was a cold, dead world, or, as it has been sometimes expressed, a burned out cinder, upon which nothing ever happened. This view was apparently due to the fact The author still regards the practice, as amongst that the men who wrote the text-books on astronomy the Wiimbaio, of exchanging wives on the approach were not the men who studied the moon. Among the of a pestilence, as a survival of group-marriage, and selenographers themselves, those astronomers who the right of access as a survival of the jus primae made a special study of the moon, there is not one, noctis and an "expiation" for individual marriage. so far as the writer is aware, who has not expressed One had thought that these two last categories had his belief that changes of some sort, volcanic or otherbeen relegated to the limbo of outworn fictions anthro-wise, occasionally occur upon our satellite. Reference is made to such men as Mädler, Schmidt, Webb, Elger, and Nieson. As the result of his lunar observations in Peru, Jamaica, and California, the writer has come to the Conclusion that physical changes do occur upon the moon, and that they may be classified under three heads, those due to volcanic action, those due to the formation and melting of hoar frost, and those due to vegetation. In the first class the classical example is that of Linné, which, according to the measurements of Lohrmann, Mädler, and Schmidt, prior to 1843, had a diameter of between four and seven miles. Its diameter at present is three-quarters of a mile. A few years ago a new crater was announced by Klein in the vicinity of Hyginus. The writer is not sufficiently familiar with this region to speak from personal experience, having but a few sketches of it, but he believes that a change there of some sort is generally admitted by selenographers. Perhaps no area of its size upon the moon has been so thoroughly examined as the floor of Plato. It has been studied at intervals of about eleven years, first in 1870 by a committee of the British Association, next by A. S. Williams and others in 1881, and again a few years later, then by the writer at Arequipa in 1892, and again this past summer in California. In each survey about forty craterlets have been mapped, and each time some new ones have been discovered, while at the same time a few of those previously observed had ceased to be visible. The original trigonometrical survey of 1870 was based upon four craterlets located near the centre of the floor, and selected as primary stations. The easternmost of these was last seen as a crater in 1888. A trace of it was suspected in 1892, but a search for it this past summer with a 16-inch telescope working under most favourable climatic conditions failed to reveal any trace of it whatever. Even the large white area upon the floor which formerly marked its position has partially disappeared. A map of the floor of Plato, based on a survey made in 1892, is given in the Harvard Annals (xxxii., plate x.). On this map the craterlet numbered 3 corresponds to craterlet number 22 of the older surveys. This craterlet was tenth in order of conspicuousness in 1870. In 1881 it had risen to the seventh place. In 1892, although carefully looked for, it could not be found, and it was entered on the map as a missing crater. A study of this region during the past summer revealed the presence of what appeared to be a large crescent-shaped bank of sand, six miles in length by from one to two miles in breadth. Its height was computed at not far from 1000 feet. It is the only object of the sort upon the floor, and the writer has so far found no previous record of its existence. When the sun is setting upon Plato it is by far the most conspicuous object within the crater walls, and was readily revealed by a 6-inch objective in Cambridge, Mass., working under very unfavourable atmospheric conditions. At sunrise it was also in part seen without difficulty under fair conditions. It seems incredible that so conspicuous an object as this should have been overlooked by all the earlier observers, had it then been visible. ation records two small white spots, one of which he thinks may have been the original crater, and the other is possibly a neighbouring hill. Both of them as shown by this sketch were evidently very small objects as compared to the present formation. The fifth observation records a bright streak passing through the spot in question and extending for about thirty miles across the floor. Evidently if the present sandbank had been in existence at that time Mr. Williams could not have failed to have seen it and recorded it upon his sketches. Between this sand heap and the crater wall a large craterlet now exists. It is, in fact, the largest upon the floor, measuring about two miles in diameter, but owing to its peculiar position, and also to the fact that it is never bright like most of the others, it can only be seen at lunar sunset, and even then is not conspicuous. Turning now to the second class of physical changes visible upon the moon, those due to the formation and disappearance of hoar frost, we find numberless examples scattered over the surface, but in most cases favourable atmospheric conditions and a large glass are necessary to render them clearly visible. dealing with any specific cases, however, it may be well to endeavour to answer some of the objections raised on theoretical grounds to the possibility of the existence of water vapour upon the moon. Before The writer believes that he himself was one of the first to point out that if water vapour existed upon the lunar surface, it must sooner or later be dissipated into outer space (Astronomy and Astrophysics, 1892, xi., p. 781). That such a dissipation must have been going on in times past seems to be inevitable, but before reaching a conclusion as to the present existence of water vapour upon the moon, there are one or two important considerations that must be taken into account. Vulcanologists are now generally agreed that the vast quantity of water, amounting to thousands, and sometimes to millions of tons, given off during volcanic eruptions is not rain water, nor yet water that has reached the interior from the ocean, but is water that either is being expelled for the first time from the earth's interior or is being expelled by heat from the rocky materials of the earth's crust with which it was previously united by the forces of crystallisation. If the earth is still discharging such large quantities of water from its interior there is no reason why the moon should not be doing the same thing. It is true the moon is smaller, but then also it began life later than the earth. The reason why the earth has oceans is that it is large enough and massive enough to retain the expelled water in that form. The moon, on the other hand, is too small to do so, and the water therefore appears scattered widely over its surface in the form of hoar frost before being dissipated into outer space. Another objection to the theory of the existence of water vapour that has been raised is the statement that there is no evidence of erosion upon the moon. This statement is clearly a mistake, but the eroded valleys are small, and it requires good atmospheric conditions to detect them. Fairly conspicuous examples, however, exist upon the central peaks of Theophilus and Eratosthenes. Although the valleys I accordingly wrote to Mr. Williams, and he kindly are small, it is hard to understand how the comparasent me a list of forty-two observations made during tively minute amount of hoar frost at present found the years 1879 to 1890, dealing with the particular in these regions could have produced so great an portion of the crater floor where this formation was effect, and we must conclude that formerly there must situated. Five of these observations were made during have been a great deal more of it. The only strong that portion of the lunar day when the object is now evidence that water in the liquid state ever existed upon conspicuous, and when it is much more so than any the surface of the moon lies in the dry river-beds. The of the craterlets upon the floor. Three of Mr. best example of these lies on the eastern slopes of Williams's observations record that nothing was Mt. Hadley, at the base of the Apennines. Another visible upon this portion of the floor. One observ-river-bed, partially fragmentary, discovered this past summer lies sixty miles due south of Conon. Although difficult objects, the former has been seen in Cambridge, Mass. A sketch of it is given in the Harvard Annals, xxxii., plate vii. Turning now from theory to fact, one of the clearest evidences of hoar frost upon the moon is found in connection with the pair of small craters known as Messier and Messier A. Sometimes one of these craters is the larger and sometimes the other. Sometimes they are triangular and sometimes elliptical in shape. When elliptical their major axes are sometimes parallel and sometimes nearly perpendicular to one another. When the sun first rises on them they are of about the same brilliancy as the mare upon which they are situated, but three days later they both suddenly turn white, and remain so until the end of the lunation. When first seen the white areas are comparatively large, especially that surrounding Messier itself, but it gradually diminishes in size under the sun's rays. By the eighth day little is left outside the crater itself, while at the end of the lunation only the bottoms and interior western walls remain They reach their minimum size five days after sunrise, when the smaller is about half a mile in diameter. They then begin to increase, the northern one attaining a length of five miles shortly before sunset. I these markings are due to white quartz, or some similar rock, it is difficult to account for their change in size. The third class of physical changes with which we shall deal the writer believes to be due to the presence of vegetation. Changes of this class are more conspicuous than those of either of the other two, and if the explanation of vegetation is admitted, both the other explanations almost necessarily follow. It is therefore important to study these changes with the greatest care. Before describing the facts, it may be well first to deal with the principal objection that has been made to the suggested explanation, namely, the lack of water on the moon in the liquid form. The reason that we believe liquid water to be lacking is that it is known that as we reduce the atmospheric pressure the boiling point of water is gradually lowered, until brilliant. The general character of these changes can be followed even with a 4-inch telescope working under only moderate atmospheric conditions. Photographs of these craters showing their varying shapes and sizes will be found in the Harvard Annals (li., p. 28). Those to whom the Annals are not accessible will find these photographs and most of the other illustrations referred to in this article in my book "The Moon." The white area surrounding Linné also shows evidence of change in size during the lunation. Soon after sunrise it measures 4" in diameter, at noon 2", and at sunset 3"-5. The change is evidently analogous to that shown by the polar caps of the earth and Mars, lunar noon in this case corresponding to midsummer for the planets, and sunrise and sunset to spring and autumn. In the crater Eratosthenes there is a brilliant white area on the summit of the central mountain range. When the sun first rises on it it measures five miles in length by two in breadth. It soon, however, begins to dwindle, and two and a half days later all is gone save two little spots, each about a mile in diameter. FIG 2.-1901, March 31, 3'5 days, 54. when we reach a pressure of 4.6 millimetres the boiling and freezing points coincide. Below this pressure ice changes at once into the gaseous form without passing through the liquid state. While, therefore, there can be no free water upon the surface of the moon, there is yet nothing to prevent it from occurring beneath the surface of the ground, retained by the capillary action of the soil. This action is so strong that, as has recently been shown by Cameron (Science, 1903, xviii., p. 758), it is capable of extracting water from a membrane against a calculated osmotic pressure of 36 atmospheres. Since on the earth plants can live on moisture which they have in turn extracted from such a soil, there seems to be no difficulty in understanding how they could live on the moon, in a soil which could thus retain considerable moisture in spite of the low atmospheric pressure. 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