214 THE POPULAR SCIENCE MONTHLY. 



in which we speak of laws of Nature, commenced, but examples of it 

 may be found in the works of Bacon, Descartes, and Spinoza. Bacon 

 employs " law " as the equivalent of " form," and I am inclined to 

 think that he may be responsible for a good deal of the confusion that 

 has subsequently arisen ; but I am not aware that the term is used by 

 other authorities, in the seventeenth and eighteenth centuries, in any 

 other sense than that of " rule " or " definite order " of the coexistence 

 of things or succession of events in Nature. Descartes speaks of " re- 

 gies, que je nomine les lois de la nature." Leibnitz says " loi ou r6gle 

 generate," as if he considered the terms interchangeable. 



The Duke of Argyll, however, affirms that the " law of gravita- 

 tion " as put forth by Newton was something more than the statement 

 of an observed order. He admits that Kepler's three laws " were an 

 observed order of facts and nothing more." As to the law of gravi- 

 tation, " it contains an element which Kepler's laws did not contain, 

 even an element of causation, the recognition of which belongs to a 

 higher category of intellectual conceptions than that which is con- 

 cerned in the mere observation and record of separate and apparently 

 unconnected facts." There is hardly a line in these paragraphs which 

 appears to me to be indisputable. But, to confine myself to the matter 

 in hand, I can not conceive that any one who had taken ordinary 

 pains to acquaint himself with the real nature of either Kepler's or 

 Newton's work could have written them. That the labors of Kepler, 

 of all men in the world, should be called " mere observation and rec- 

 ord," is truly wonderful. And any one who will look into the " Prin- 

 cipia," or the " Optics," or the " Letters to Bentley," will see, even if 

 he has no more special knowledge of the topics discussed than I have, 

 that Newton over and over again insisted that he had nothing to do 

 with gravitation as a physical cause, and that when he used the terms 

 attraction, force, and the like, he employed them, as he says, " mathe- 

 matice " and not "physice" 



How these attractions [of gravity, magnetism, and electricity] may be per- 

 formed, I do not here consider. "What I call attraction may be performed by 

 impulse or by some other means unknown to me. I use that word here to sig- 

 nify only in a general way any force by which bodies tend toward one another, 

 whatever be the cause.* 



According to my reading of the best authorities upon the history 

 of science, Newton discovered neither gravitation nor the law of 

 gravitation ; nor did he pretend to offer more than a conjecture as to 

 the causation of gravitation. Moreover, his assertion that the notion 

 of a body acting where it is not, is one that no competent thinker 

 could entertain, is antagonistic to the whole current conception of at- 

 tractive and repulsive forces, and therefore of " the attractive force of 

 gravitation." What, then, was that labor of unsurpassed magnitude 

 and excellence and immortal influence which Newton did perform ? 



* " Optics," query 31. 



