ON THE HISTORY OF TERRESTRIAL PHYSICS. 743 



knowledge of any part of physics, except astronomy and natural history: 

 their opinions were in general mere speculations, derived from fancy, and 

 inapplicable to the real phenomena of nature. Opinions such as these wvU 

 only require to be so far examined, as to enable us to trace the imperfect 

 rudiments of discoveries, which were only completed after intervals of many 

 ages. 



The Chinese are said to have been acquainted with the use of the compass 

 above 3000 years ago; but in such accounts, it is impossible to ascertain how 

 far the spirit of national vanity may have induced a historian to falsify his 

 dates. It has been conjectured that the death of Numa, like that of Pro- 

 fessor llichniaun, ,was occasioned by some unguarded experiments on the 

 electricity of the atmosphere, which drew on him the effects of a thunderstorm 

 that was passing by. If, however, the fact was such, the experiments must 

 probably have been suggested rather by an accidental discovery of the light 

 on the point of a spear, than by any rational opinions respecting the nature 

 of the ethereal fire. 



Thales is the most ancient of the Grecian philosophers, who appear to have 

 seriously studied the phenomena of nature. He supposed water to be the 

 general principle from which all material things are formed, and into which 

 they are resolved; an opinion which was without doubt suggested to him 

 by the obvious effects of water in the nutrition of plants and of animals. He 

 particularly noticed the properties of the magnet, which had been before 

 observed to attract iron, as well as the effect of friction in exciting the elec- 

 tricity of amber; and he attributed to both of these substances a certain 

 degree of animation, which he considered as the only original source of motion 

 of any kind. 



Anaximander appears to have paid some attention to meteorology ; he 

 derived the winds from the rarefaction of the air, produced by the operation 

 of heat: thunder and lightning he attributed to the violent explosion or 

 bursting of the clouds, which he seems to have considered as bags, filled with 

 a mixture of wind and water. The same mistaken notion was entertained 

 by Anaximenes, who compared the light attending- the explosion, to 

 that which is frequently exhibited by the sea, when struck with an oar. 



