In a communication to the American Journal, Professor Kirkwood discusses the question—Does the motion of the inner satellite of Mars disprove the nebular hypothesis? This satellite he remarks is within three thousand four hundred miles of the planet's surface, and completes three orbital revolutions in less than a Martial day. How is this remarkable fact to be reconciled with the cosmogony of Laplace? The Professor then remarks that there is some similarity between the movements of the satellites and those of the rings of Saturn. The rings are composed of clouds of exceedingly minute planetoids, and while the outer ring revolves in a period somewhat greater than that of Saturn itself, 'the inner visible edge of the dusky ring completes a revolution in about eight hours. These rings,' in the words of Professor Tait, 'like everything cosmical, must be gradually decaying, because in the course of their motion round the planet there must be continual impacts among the separate portions of the mass; and of two which impinge, one may be accelerated, but at the expense of the other. The other falls out of the race, as it were, and is gradually drawn in towards the planet. The consequence is that, possibly not so much on account of the improvement of telescopes of late years, but perhaps simply in consequence of this gradual closing in of the whole system, a new ring of Saturn has been observed inside the two old ones, called from its appearance the crape ring, which was narrow when first observed, but is gradually becoming broader. That crape ring is formed of the laggards which have been thrown out of the race, and are gradually falling in towards Saturn's surface.' It is then suggested that, by a process similar to that here described, the phenomena of the Martial system may have been produced, and the argument concludes thus: 'Unless some such explanation as this can be given, the short period of the inner satellite will doubtless be regarded as a conclusive argument against the nebular hypothesis.'
In a paper read at a meeting of the Royal Astronomical Society, Mr Brett argues against the hypothesis that Mars is in a condition similar to that of the earth. He grounds his conclusion on the fact that in all his observations of Mars he has seen no clouds in the atmosphere thereof. That atmosphere is very dense, of great bulk, and is probably of a temperature so high that any aqueous vapour contained therein is prevented from condensation. Mr Brett implies that the glowing red colour of the middle of the disk is glowing red heat; and he remarks, in terrestrial experience there is always an intermediate phenomenon between vapour and snow, namely opaque cloud; and the absence of this condition seems fatal to the hypothesis that the white polar patch, as hitherto supposed, consists of snow. According to Mr Brett this patch is not only not snow; constitutes no part of the solid mass of the planet; but is nothing more than a patch of cloud, 'the only real cloud existing in Mars.'
From particulars published in the Quarterly Journal of the Geological Society, it appears that metallic copper and copper ore have been discovered along a tract of country in Nova Scotia, that the specimens when analysed at Swansea yielded satisfactory results, and that 'Nova Scotia may soon appear on the list of copper-producing countries, it being confidently expected that during the approaching summer fresh localities will be proved to contain copper-bearing veins.' And shifting the scene, we learn from the same Journal that in the South African Diamond Fields, two claims in Kimberley Mine, comprising eighteen hundred square feet, have yielded twenty-eight thousand carats of diamond; that at Lyndenburg, in the Transvaal country, most of the alluvial gold is supplied by Pilgrim's Rest Creek, the gold being coarse and nuggety, in well-rounded lumps, some of which, ten pounds in weight, are worth from seventy-six to eighty shillings an ounce; and that near the Oliphant River cobalt ore is found, of which a hundred tons have been sent to England. The same locality yields beryls, and is believed to be rich in other minerals.
Compressed air on being released from pressure can be cooled down to a very low temperature by throwing into it a jet of cold water. Advantage has been taken of this fact in contriving a new refrigerator or freezing chamber; and we are informed that at a trial which took place with a view to commercial purposes, 'in half an hour after commencing to work the machine, the thermometer within the freezing chamber stood at twenty degrees below zero; the interior of the chamber was covered with hoar-frost half an inch thick, bottles of water were frozen solid, and the general temperature of the room in which the freezing chamber stands was reduced to thirty degrees Fahrenheit.' It is clear that by this invention a very cheap way of producing ice and maintaining coolness has become available; and that it should have been adopted by a Company for use on board ship to keep meat fresh during the voyage from Canada is what might be expected. Bearing in mind that in April of the present year the United States sent to England more than eight million pounds of meat, the importance of the new cooling method will be appreciated. Moreover, it may be applied to many other purposes which require a low temperature.
Another step has been taken towards diminishing the risk of railway travelling. Experience has shewn that the danger most to be dreaded is collision; and that collision is brought about by defective signals. The interlocking system of signals is good, and the block-system is good; but they have failed in critical moments. The manager of the Railway Signal Works at Kilburn has invented a method which combines the two systems, and, as we are informed, has thereby 'dislodged the last atom of human fallibility' from railway signalling. Time will prove.
The block-system has been adopted, with endeavours to improve it, on some of the principal lines in France; and the companies point to statistics which shew that railway travelling is safer in France than in Belgium or England; there being not more than one death to forty-five millions of travellers.
Professor Marsh's address to the meeting of the American Association for the Advancement of Science cannot fail to interest all readers who desire to learn something of the Introduction and Succession of Vertebrate Life in America. It is a subject very inviting, and very difficult to trace the succession from fishes to amphibia, reptiles and birds, and onwards to mammals; but cannot be properly discussed without the aid of much dry scientific detail. We shall content ourselves therefore with a few points in the address which admit of presentation in a popular form. 'During the Triassic time,' says Professor Marsh, 'the Dinosaurs attained in America an enormous development both in variety of forms and in size. The Triassic sandstone of the Connecticut valley has long been famous for its fossil footprints, especially the so-called bird-tracks, which are generally supposed to have been made by birds. A careful investigation, however, of nearly all the specimens yet discovered has convinced me that most of these three-toed tracks were certainly not made by birds; but by quadrupeds which usually walked upon their hind-feet alone, and only occasionally put to the ground their smaller anterior extremities.'
According to present knowledge, the earliest appearance of birds in America was during the Cretaceous period. Among them was one to which the name Hesperornis has been given. It was aquatic, nearly six feet in length, had jaws with teeth set in grooves, rudimentary wings, and legs similar to those of modern diving-birds. We have it on the authority of Professor Marsh that this strange creature 'was essentially a carnivorous swimming ostrich.'
Coming to the Miocene period, we are told of the Brontotherium, an animal nearly as large as the elephant, but with much shorter limbs. A countryman looking at the skeleton of one of these monsters in the museum at Newhaven, was heard to say: 'Adam must have had a bad time of it when he branded that critter there.' It was succeeded by the equally huge Chalicotherium. And a little later we have the statement that 'the Marsupials are clearly the remnants of a very ancient fauna which occupied the American continent millions of years ago, and from which the other mammals were doubtless all derived, although the direct evidence of the transformation is wanting.'
It has long been supposed that the New World was peopled by migrations from the Old World. Professor Marsh holds a directly opposite opinion, whereby an interesting question is presented for discussion. The surveys and explorations carried on of late years by the United States government have brought to light such an amazing number of fossils, indicative of more, that the museums in America will soon be the largest and the richest in specimens in the world. On the other hand, we may point to Central Asia, and suggest that when that vast country shall be thoroughly explored, fossil relics may be discovered more diversified and interesting even than those of America.