188 



SCIENCE. 



[Vol. Vm., No. 186 



tense look of cunning' as he set about to obtain the 

 cane. 



First ag^reeing that the terms ' reflex action,' ' in- 

 stinct,' and ' reason ' shall be defined according- to the 

 definitions of Dr. Romanes (' Animal intelligence,' p. 

 17), the action, or series of actions, executed by No, 

 2 must have been, wholly or in part, either reflex, 

 instinctive, or rational. If reflex, there must have 

 been : — 



(a) Particular and often recurring stimuli, to have 

 given rise to the acts of No. 2 ; and also, 



(6) The acts must have been adaptive, although not 

 intentional. 



Manifestly, these two prime conditions did not ob- 

 tain, and therefore the acts of No. 2 were not reflex, 

 either in whole or in part. If instinctive, then the 

 acts of No. 2 must have been performed " without 

 necessary knowledge of the relation between means 

 employed and ends attained, but similarly performed 

 under similar and frequently recurring circumstances 

 by all the individuals of the same species." 



1® Had No. 2 ceased his current-making when he 

 obtained the piece of wood, his act might possibly 

 have been in part instinctive ; but having obtained 

 one object by this means, he seems to set the same 

 cause in action to gain another object, which he con- 

 ceives to be similarly conditioned, and when, appar- 

 ently by new observations (data), finding that this 

 second object is confined by a force greater than that 

 which he can command by his water-current, he de- 

 sists immediately from his exertions, it is evident 

 that three several mental processes have occurred, to 

 wit : — 



(a) The employment of like causes to produce like 

 effects. 



(6) The exercise of a certain amount of memory 

 (individual education by experience). 



(c) The correct estimation of the difference in 

 force, exerted upon the cane, between the water- 

 current of his making and the confining power of his 

 mate's paw, e. g. , judgment. 



2° By the conditions of our definition, it would be 

 necessary, in order that these acts of No. 2 might be 

 instinctive, that the same should be observed of the 

 majority of polar bears when similarly conditioned. 

 An appeal to facts shows that these acts are rarely 

 executed by bears. Hence it follows that the said 

 acts of No. 2 were not, either in part or in whole, 

 instinctive. Finally, by the conditions of the prop- 

 osition, these acts, being neither reflex nor instinct- 

 ive, must be rational, or else did not take place, 

 e. g., either reason must exist in certain bears of the 

 polar species, or the mind of man must refuse to 

 think of the acts of said bears. The only attempt at 

 the vitiation of the foregoing argument is conceived 

 to exist in the fact that it rests upon but one obser- 

 vation. 



James P. Marsh. 



The eccentricity theory of the glacial period. 



Croll's eccentricity theory of the glacial period is 

 certainly an attractive theory. The ingenuity and 

 learning of its author have merited and received uni- 

 versal respect. The proposal thus to link together 

 by one additional tie the sciences of astronomy and 

 geology, is in harmony with that profound sense 

 of the unity of nature, which is a dominant senti- 

 ment in modern science. In utter despair of the 

 possibility of constructing any reliable time estimates 



by measuring the amount of erosion or deposition, 

 every geologist would gladly welcome the opportu- 

 nity of importing into his science something of the 

 chronological definiteness which has been the boast 

 of the astronomer. And it must, I think, be con- 

 ceded that no very satisfactory explanation of a 

 glacial period by means of purely terrestrial condi- 

 tions has been proposed. 



Nevertheless, there has always been a considerable 

 degree of skepticism in regard to the fundamental 

 conception of the eccentricity theory. The question 

 whether the conditions of aphelion winter and peri- 

 helion summer, in an epoch of great eccentricity, 

 would tend to accumulate snow and ice, and produce 

 a glacial period in the hemisphere so conditioned, 

 has never been so answered as to command universal 

 assent. Indeed, J. J. Murphy has argued, with much 

 plausibility, that the glaciated hemisphere would 

 be the one with perihelion winter and aphelion sum- 

 mer.' Others have believed that there would be no 

 appreciable effect in the direction of glaciation in 

 either hemisphere. I desire to call attention to a 

 class of well-known facts whose bearing upon the 

 question has not, I think, been adequately regarded. 

 A very brief preliminary discussion will suffice to 

 show the bearing of the facts referred to. 



There would evidently be two marked contrasts in 

 the character of the seasons between the two hemi- 

 spheres at an epoch of high eccentricity. The hemi- 

 sphere with aphelion winter would have a long win- 

 ter and a short summer, while the other hemisphere 

 would have a short winter and a long summer. 

 Again, the hemisphere with aphelion winter would 

 have extremes of heat and cold, its summer being 

 very hot and its winter very cold, while the climate 

 of the other hemisphere would approximate a mean 

 throughout the year. It is by no means certain that 

 the effects of these two contrasts upon the matter of 

 glaciation would be in the same direction. As re- 

 gards the difference in the length of the seasons, I 

 suppose there can be no doubt that increased length 

 of winter would tend to glaciation. Other things 

 being equal, the longer the winter, the larger would 

 be the proportion of precipitation in the form of 

 snow, and the smaller the proportion in the fo3 m of 

 rain. And increased snow fall would certainly tend 

 to accumulation of snow and ice. 



But what would be the effect of the difference in 

 the intensity of the seasons ? Would glaciation be 

 favored by cold winters and hot summers, or by mild 

 winters and mild summers — by a climate of ex- 

 tremes, or by a climate of means ? It seems to me 

 that a comparison oT the northern and southern 

 hemispheres at present, in the matter of glaciation, 

 will suggest an answer to this question. The present 

 value of the eccentricity of the earth's orbit is so 

 small that its climatic effects are completely masked 

 by geographical conditions. The northern hemi- 

 sphere now has th6 perihelion winter, and the south- 

 ern hemisphere the aphelion winter. So far, there- 

 fore, as astronomical conditions control climate, the 

 northern hemisphere should have a climate of means, 

 and the southern hemisphere of extremes. But this 

 relation is completely reversed by geographical con- 

 ditions. The great amount of land in the northern 

 hemisphere gives that hemisphere a climate of ex- 

 tremes, while the vast expanse of water in the south- 

 ern hemisphere produces a climate of means. This 



1 Quarterly journ. of geolog. soc, xxv. 350, 1869 ; Amer. 

 journ. science, [2] xlix. 115, 187U. 



