714 



SCIENCE. 



[N. S. Vol. VIII. No. 203. 



The earth, for example, as it would appear to 

 an observer on the moon, with the daily pas- 

 sage of its continents from light to shadow, and 

 annually recurring seasonal changes, requires 

 an exercise of the imagination of a high order. 

 In a similar way, various hypotheses to account 

 for the origin of the earth, the larger move- 

 ments of the atmosphere and of the ocean, the 

 flow of glaciers, the origin of volcanoes, etc., 

 call not only for a knowledge of facts and prin- 

 ciples, but the power to group them in the 

 imagination and follow step by step the many 

 changes that are involved. The student of na- 

 ture has to create in his own mind pictures of 

 the workings of nature ranging in scale from 

 the movements of molecules to the revolution 

 of planets and siderial systems. It is in this 

 field that the book before us excels. One can- 

 not read its glowing pages without having his 

 imagination greatly stimulated. The rigid 

 boundaries that circumscribe systematic treaties 

 are very properly ignored, and freedom given 

 the imagination to build castles, or rather 

 cathedrals, in the air, to illustrate Nature's 

 architecture. 



One phase of the use of imagination in scien- 

 tific research is the trial by hypotheses. As 

 many plausible explanations as possible of a 

 given phenomena are invented, and the errone- 

 ous ones eliminated by careful tests. In this 

 process of multiplying of hypotheses but few 

 men excel the author of the book under re- 

 view. The search for a true explanation neces- 

 sitates the destruction of many trial explana- 

 tions. Every scientific investigator, it has been 

 said, lives in the midst of a cemetery of defunct 

 hypotheses. Strange as it may seem to the 

 uninitiated, every true investigator tries to kill 

 his own hypotheses, in order that only the 

 strong may live. His zeal in this direction be- 

 ing excelled only by the desire to kill the 

 hypotheses proposed by others. In the in- 

 tangible world of ideas, as in the organic realm, 

 the fittest survive. To most readers of popular 

 science this struggle is practically unknown, 

 and the hypotheses presented to them are ac- 

 cepted as well established laws. For this, if 

 for no other reason, only such hypotheses as 

 have been exposed in the searchlight of criti- 

 cism, and have been generally accepted by 



specialists in the particular field of science to 

 which they pertain, deserve a place in popular- 

 science books. It is in this connection that the 

 volume before us seems most widely open to 

 criticism. 



An explanation of the movements of the 

 tides and the flow of glaciers placed side by 

 side before the general reader or the student 

 just entering on the study of nature, are ac- 

 cepted as equally worthy of credence, and are 

 apt to take such firm root in the mind that a 

 shock is felt when one of them has to be modi- 

 fied or rejected. 



The explanation of the flow of glaciers, and 

 especially the view that continental glaciers, in 

 their central and deeper portions, float on a 

 cushion of water or of half-melted ice, for the 

 reason, if no counteracting agency exerted an 

 influence, that the ice at the bottom of such a 

 glacier would melt because of the presence of 

 its own mass, the melting point of ice being 

 lowered by pressure, is one of the many attract- 

 ive hypotheses that have sprung from Profes- 

 sor Shaler's fruitful brain, but one not generally 

 accepted by glacialists. This tendency to give 

 precedence lO one's own hypotheses is again 

 manifest in discussing the nature and origin of 

 volcanoes. The changes which water-charged 

 sediments would undergo if depressed to a 

 depth of many thousands of feet (Shaler sug- 

 gests twenty miles!) is elaborated as the main 

 explanation of the origin of volcanoes. While 

 this hypothesis fascinates the mind, and ex- 

 plains many of the facts observed during vol- 

 canic eruptions, notably the vast volumes of 

 steam given forth, it has not withstood the 

 tests of criticism in such a way as to warrant 

 its presentation to the public as the sole and 

 final explanation of volcanic phenomena. 



While it is not the province of a reviewer to 

 dwell on typographical errors, I will note one 

 slip for which having been called to account 

 myself, I can warn others against. In the 

 English translation of Palmieri's book on the 

 Eruption of Vesuvius in 1872, a certain gulch 

 on the side of the mountain is called the 'Atria 

 del Cavallo,' the word atria, according to the 

 dictionaries, should be atrio. This mistake has 

 been repeated on page 285 of the book under 



