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TEE POPULAR SCIEXCE MOXTELY.—SUPPLEMEXT. 



By this grand generalization Newton reduced 

 the laws of the celestial motions to a form so 

 elementary, simple, and comprehensive, that no 

 further reduction seems possible in our present 

 state of knowledge. Attempts have been made 

 to show that gravitation is itself the result of 

 discoverable causes ; but they appear to me en- 

 tirely unphilosophical, since the causes into which 

 they would resolve gravitation are more complex 

 than gravitation itself. But for our present pur- 

 pose it is not necessary to concern ourselves 

 whether gravitation may arise from some more 

 subtile principle, as yet undiscovered. The point 

 which I wish you to grasp is the entire compre- 

 hensibility of the law, as it now stands. There 

 is no mystery surrounding it. When I say that 

 any body left unsupported will fall toward the 

 centre of the earth until it meets with the earth 

 itself, or some other obstacle to its further full, 

 you know exactly what I mean and what are the 

 results of the law which I enunciate. In a cer- 

 tain sense we might say that the laws of Nature 

 are simply general facts, distinguished from spe- 

 cial facts by their dependence upon certain an- 

 tecedent conditions. Considered as such, there 

 can never be any doubt as to their meaning or 

 results. There is no profound philosophy in- 

 volved in their action or expression, any more 

 than there is in such statements as that all un- 

 supported bodies fall toward the centre of the 

 earth ; that gunpowder, when touched by fire, 

 suddenly changes to an incandescent gas ; that 

 water, at ordinary pressure, changes to steam at 

 a temperature of 212°. 



Now, scientific investigators are earnestly en- 

 deavoring, each in his own sphere, to do for the 

 whole of Nature what Newton did for the laws of 

 planetary motion — to find and announce the ele- 

 mentary principles which connect all the links of 

 the endless chain which symbolizes her course. 

 The student of chemistry cannot doubt that the 

 innumerable properties of the various compounds 

 which he studies arise from the play of certain 

 attractive and repulsive forces among the element- 

 ary molecules of the matter of which these com- 

 pounds are formed. Could he only leain the law 

 according to which these forces act, chemistry 

 might become very largely a deductive science, 

 and the properties of compounds might be pre- 

 dicted in advance, as the astronomer predicts 

 the conjunctions of the planets. The idea now 

 entertained by those who see furthest in this 

 direction is that all the physical properties 

 of matter depend upon and may be reduced to 

 certain attractive and repulsive forces, acting 



among the ultimate atoms of which matter is 

 composed. 



It may also be supposed that all the opera- 

 tions of the vital organism, both in men and ani- 

 mals, depend, in the same way, upon molecular 

 forces among the atoms which make up the or- 

 ganism. The operation of forces unknown to 

 chemistry must, indeed, be presupposed ; but 

 there is no reason to suppose that these forces 

 are less simple than chemical ones. Some would 

 even go so far as to explain the facts of conscious- 

 ness in this way. The philosophy of this expla- 

 nation belongs, however, to another department 

 of thought — that of scientific materialism — into 

 which we cannot at present enter. 



The most startling attempts in the direction 

 I have indicated are those which are designed to 

 show that those wonderful adaptations which we 

 see in the structure of living animals, and which 

 in former times were attributed to design, are 

 really the result of natural laws, acting with the 

 same disregard to consequences which we see in 

 the falling rock. The philosophy of Darwinism 

 and the theory of evolution will be at once brought 

 to your mind as forming the modern system of 

 explanation tending to this result. On these 

 theories, the eye was not made in order to see, 

 nor the ear in order to hear, nor are the number- 

 less adaptations of animated beings to the con- 

 ditions which surround them in any way the 

 product of design. Absurd as this theory ap- 

 pears at the first glance, and great as is the anx- 

 iety to secure its rejection, the question of its 

 truth is to be settled only by a careful scientific 

 study of the facts of Nature and the laws of he- 

 reditary descent. The principle which is to aid 

 in its settlement is universally admitted in quar- 

 ters where it is fully understood. We are not to 

 call in a supernatural cause to account for a re- 

 sult which could have been produced by the action 

 of the known laws of Nature. The question, then, 

 is whether these laws of hereditary descent and 

 of natural selection are adequate to account for 

 the gradual growth of such organs as the hand, 

 the eye, and the ear, and for all the adaptations 

 which we see in Nature. If they are, it would be 

 idle to call in any other cause, except we place it 

 behind the laws ; and if we place it behind those 

 laws, we must equally place it behind all others. 

 Of course, such a cause lies beyond the field of 

 sight, and does not, therefore, belong to scientific 

 observation. Granting the theory, then, so far as 

 the eye of Science can penetrate, the whole re- 

 sult is brought about by laws actiDg in seemingly 

 blind disregard of consequences. 



