25 8 THE POPULAR SCIENCE MONTHLY. 



We are to consider this evening the phenomena of crystallization ; 

 but, in order to trace out the genesis of the notions now entertained 

 upon the subject, we have to go a long way back. 



In the drawing of a bow, the darting of a javelin, the throwing of 

 a stone, in the lifting of burdens, and in personal combats, even savage 

 man became acquainted with the operation of force. His first efforts 

 were directed toward securing food and shelter ; but ages of disci- 

 pline during which his force was directed against Nature, against his 

 prey, and against his fellow-man taught him foresight. He laid by 

 at the proper season stores of food, and thus obtained time to look 

 about him, and become an observer and inquirer. He discovered two 

 things, which now more specially interest us, and sent down to us the 

 knowledge of his discovery. He found that a certain resin dropped 

 from the amber-tree possessed, when rubbed, the power of drawing 

 light bodies to itself, and of causing them to cling to it ; and he also 

 found that a particular kind of stone exerted a similar power over a 

 particular kind of metal. I allude, of course, to the loadstone, or nat- 

 ural magnet, and its power to attract particles of iron. Previous ex- 

 perience had enabled our early inquirer to distinguish between a push 

 and a pull. In fact, muscular efforts might be divided into pushes 

 and pulls. Augmented experience showed him that in the case of the 

 magnet, pulls and pushes attractions and repulsions were also ex- 

 erted ; and, by a kind of poetic transfer, he applied to things external 

 to himself the conceptions derived from the exercise of his own mus- 

 cular power. The pushes and pulls of the magnet and of the rubbed 

 amber were to him also force. 



In the time of the great Lord Bacon, the margin of these pushes 

 and pulls was vastly extended by Dr. Gilbert, a man probably of 

 firmer fibre, and of finer insight, than Bacon himself; who, moreover, 

 was one of the earliest to enter upon that career of severe experi- 

 mental research which has rendered our science almost as stable as 

 the system of nature which it professes to explain. Gilbert proved 

 that a multitude of other bodies, when rubbed, exerted the power 

 which thousands of years previously had been observed in amber. In 

 this way the notion of attraction and repulsion in external Nature was 

 rendered familiar. It was a matter of experience that bodies between 

 which no visible link or connection existed, possessed the power of 

 acting upon each other ; and the action came to be technically called 

 " action at a distance." 



But out of experience in science there always grows something 

 finer than mere experience. Experience, in fact, only furnishes the 

 soil for plants of higher growth ; and this observation of action at a 

 distance furnished material for speculation upon the largest of all 

 problems. Bodies were observed to fall to the earth. Why should 

 they do so ? The earth was proved to roll round the sun ; and the 

 moon to roll round the earth. Why should they do so ? What pre- 



