SOME SCIENTIFIC BOOKS.*
WE have already spoken in terms of praise of the first volume of Messrs. Chamberlin and Salisbury's Geology, which was devoted to the processes by which the earth has been moulded into its present shape. The second and third volumes, which now complete the work, contain a full and interesting account of the history of the earth, as we can read it in the geological record. The authors begin with the long-distant age when the earth was "a fluid haze of light," and describe the various hypotheses which have been put forward to account for its concretion. The original nebular hypothesis, as suggested by Kant and worked out by Laplace, is no longer tenable in its complete form, though undoubtedly it is a near approach to the facts. But it is fatally injured by the discovery of certain satellites which revolve in a direction contrary to that of the planet on which they attend, and further mathematical investigations show that Laplace's reasoning was not always correct. Sir Norman Lockyer's meteoritic hypothesis is then examined, and the authors go on to give their reasons for preferring the third or planetesimal hypothesis, which is mainly due to Mr. Chamberlin and Professor Moulton. This maintains that the parent nebula of the solar system was of the spiral type—like the famous nebula in Andromeda—and that it was formed of innumerable small bodies, or "planetesimals," revolving about a central gaseous mass. The evolution of the system consisted in the gradual aggregation of most of these small bodies into a few large planets. Although it cannot be said that this hypothesis is yet accepted by the majority of astronomers, it must be admitted that it comes nearer than its predecessors to offering a coherent explanation of the facts now existing. The authors give an admirable account of the various stages through which the earth has passed since it became solid, and their beautifully illustrated volumes form one of the most complete and trustworthy geological treatises which have yet been published. The work reflects great credit on the University of Chicago, from which it comes.
Mr. Gustav Mann's account of the Chemistry of the Proteids originated as a translation of Dr. Cohnheim's well- known Chemie der Eiweiskorper, but has been expanded into a book which has serious claims to originality, though it is still based on the work of the Heidelberg Professor, who has given his cordial approval to this extension of his enterprise. It is too technical for a detailed review in our columns, but may be strongly recommended to all Who are working at this abstruse but very important subject Dr. Mann is himself a biologist in the first place, and throughout it is the biological aspect of chemistry which he has borne in mind. He aims at bridging over the gulf between those who hold that life is the outcome of a special vital principle which can never be wholly explained by chemistry and physics, and those who think that the laws which hold good for inorganic bodies are competent to expound the phenomena of organic life. This is an interesting and valuable piece of work, which should be of great assistance towards the reading of the momentous riddle of life.
Dr. Guppy is well known as an authority on the natural history of the Pacific islands. The first volume of his Obser- vations, based on the journeys which he made from 1896 to 1899, was reviewed in our columns three years ago. The second volume now lies before us, and deserves very respectful treatment. It bears as its sub-title "Plant-Dispersal," and is a most valuable contribution to the important subject of the distribution of botanical species. The islands of the Pacific obviously call the attention of a naturalist who knows them so well as Dr. Guppy to this subject. Many of them are found to have risen from the deep —by the labour of the minute coral-builders—in com- paratively recent geological times. How is it that they exhibit so many of the botanical forms which are found • (1) Geology. By 1.0. Chamberlin and B. Salisbury. Vols. II. ad IlL London : J. Murray. [21s. net.]—(2) Chemistry of the Proteicls. By Gustav Mann. London : Macmillan and Co. [1.5s. net. J—(2) Observations of a Naturalist in the Pacific. By H. B. Guppy. Vol. II. game publishers. [219. net.]—(4) Turbines. By W. H. Stuart thrnett. London : O. Bell and gohs. [Be. 6.1. net.]—(5) Joseph Priestley. By T. E. Thorpe. London : J. 2d. Dent and Co. [2s. 6d. net] growing on older islands, or on the distant mainland? We can hardly suppose that identical plants have developed in these different environments, and the problem is to find out how they have been distributed over such remote and minute areas. Dr. Guppy has found an answer to this question itt the study of ocean-currents and the buoyancy of certain seeds. Alike in our own islands and on the tropical shores of South America, he finds that plants may be divided into two great classes,—those with seeds which float in water, and those with seeds which sink or which are so frail as to be destroyed by long immersion. "There has been at work through the ages a great sorting-process, by which the plants belonging to the group first named have been mostly gathered at the coast. Its operation may be also observed within the limits of a genus, where the species possessing seeds or fruits that float is stationed at the coast, whilst the species with seeds or fruits that sink makes its home inland." It is probable that Nature has never troubled herself—so to speak—about providing a method of plant-dispersion, and that the buoyancy of certain seeds is an accidental attribute. But it has had a far-reaching effect upon the flora of islands, which have beeti mainly stocked by seeds drifted to their shores by ocean-currents. These currents are so arranged that the continent of America is a distributor, and not a recipient, of plants, so that "all cosmopolitan tropical beach-plants that are dis- persed by the cumets have their homes in America." Birds also act, on a smaller scale, as plant-distributors, by means of the indigestible seeds which they swallow on one land and plant on another in their droppings. Dr. Guppy has worked out this principle with great completeness, and his book is the most thorough and scientific contribution yet made to the history of plant-dispersal in the Pacific.
The development of the steam-turbine in recent years promises to mark the greatest advance in our uses of machinery since the steam-engine itself was invented. The ordinary reciprocating engine essentially consists of a piston which is driven backwards and forwards in a straight line, and requires some additional device for the production of that rotary motion which is generally the desired result. This involves the waste of a considerable amount of energy, used up in alternately stopping and starting the heavy piston and its connected gear, and causes much unnecessary vibration. It is clear that a valuable economy in power is produced by the application of steam or any other gas to the direct pro- duction of rotary motion, and the consequent elimination of the reciprocating parts. Mr. Stuart Garnett has been moved to write his lucid and excellent account of Turbines—as these direct rotary engines are called—by his experience of "the extraordinary ignorance prevailing among men of some degree of technical knowledge, and even among competent'engineem of the very nature of this, one of the simplest and most beautiful among modern machines, the heir of all the ages of engineering experience and development." The earliest form of turbine is the water-wheel, which was probably the oldest of the power-giving machines invented by man ; it was described by Vitruvius in the fourth century B.C., much in the form in which it may still be seen in out-of-the-way parts of the country. From the original undershot wheel the modern water-turbine—used wherever it is necessary to apply water-power to large undertakings, ad at Niagara or Tivoli"- bas been evolved. This machine is fully described in the first part of Mr. Garnett'i book. The second part deals with the modern steam-turbine. Hero of Alexandria, in hie primitive and toy-like steam-engine, used the steam directly to drive a wheel, and we are now returning to that earliest method. The interlude of the reciprocating engine Was due to the fact that the &IA modern use of steam was to drive the pumps Of deep mines, for which a reciprocating motion was desirable ; and for some reason the later inventors went On laboriously devising means of converting this reciprocating Motion into that of turning a wheel. Mr. Parsons was the first to produee a really efficient steam-turbine, and it is probable that the steattpuser of the future will rank his name °lily secoed to that of Watt.
Joseph Priestley, the "honest heretic," was a very interesting figure in the history of science, not only for the persecution which be so unjustly incurred, but for his chemical researches. He not only gave us soda-water and all those aerated drinks which we nowadays find indis- pensable in hot weather, but he helped to lay the foundation of the chemistry of gases. Dr. Thorpe has given us an admirable account of Joseph Priestley in "English Men of Science," and the concluding chapter, in which Priestley's scientific work is largely described in his own words, could hardly have been better compiled.
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