24 c<)SMos. 



Gilbeit, as early as 1600, regarded magnetism as a ibrcft in* 

 herent in all matter. So midetermined was even Kewtoii, 

 the profound and experienced thinker, regarding the " ulti- 

 mate mechanical cause" of all motion. 



It is indeed a brilliant effort, worthy of the human mini, 

 lo comprise, in one organic v/hole, the entire science of na* 

 ture from the laws of gravity to the formative impulse (ni- 

 sus formativus) in animated bodies ; but the present imper- 

 fect state of many branches of physical science offers innu- 

 merable difficulties to the solution of such a problem. The 

 imperfectibility of all empirical science, and the boundless- 

 ness of the sphere of observation, render the task of explain- 

 ing the forces of matter by that which is variable in matter, 

 an impracticable one. "VYhat has been already perceived by 

 no means exhausts that which is perceptible. If, simply re- 

 ferring to the progress of science in modern times, we com- 

 pare the imperfect physical knowledge of Gilbert, Robert 

 Boyle, and Hales, with that of the present day, and remem- 

 ber that every few years are characterized by an increasing 

 rkpidity of advance, we shall be better able to imagine the 

 periodical and endless changes wliich all physical sciences 

 are destined to undergo. Kew substances and new forces 

 will be discovered. 



Although many physical processes, as those of light, heat, 

 and electro-magnetism, have been rendered accessible to a 

 mathematical investigation by being reduced to motion or vi 

 brations, we are still without a solution to those often mooted 

 and perhaps insolvable problems : the cause of chemical dif- 

 ferences of matter ; the apparently irregular distribution of 

 the planets in reference to their size, density, the inclination 

 cf their axes, the eccentricity of their orbits, and the num- 



fore I'educed by liim, as previously by Goodwin Knight {Philos. Tran^ 

 act. 1748, p. 264), to the conflict of two elementary forces. In the at- 

 omic theories, which were diametrically opposed to Kant's dynamic 

 views, the force of attraction was referred, in accordance with a view 

 specially promulgated by Lavoisier, to the discrete solid elementary 

 molecules of which all bodies are supposed to consist; while the force 

 of repulsion was attributed to the atmospheres of heat surrounding all 

 elementary corpuscles. This hypothesis, which regards the so-called 

 saloric as a constantly expanded matter, assumes the existence of two 

 elemeutaxy substances, as in the mythical idea of two kinds of &ilier. 

 (Newton, Gpiics, qiiery 28, p. 339.) Here the question arises, What 

 causes this caloric matter to expand? Considerations on the density 

 of molecules in comparison with that of their aggregates (the entiro 

 body) lead, according to atomic hypotheses, to the result, that the dis- 

 tance between elementary corpuscles is far greater than their diunetera 



