BIOGRAPHICAL INDEX 



tory storage battery. His battery was con- 

 structed of sheets of lead immersed in dilute 

 sulphuric acid. 



Plato, i, 1 80. Born at JEg'ma, 429 or 427 

 B.C.; died at Athens, 347. Greek philosopher. 

 He was a great ethical teacher, but seems to 

 have had no clearly defined opinions as to the 

 mechanism of the universe; no clear conception 

 as to the origin of development of organic be- 

 ings; no tangible ideas as to the problems of 

 physics; no favorite dreams as to the nature of 

 matter. 



Playfair, John, iii, 131. Born at Ben vie, For- 

 farshire, March 10, 1748; died at Edinburgh, 

 July 19, 1819. Scottish physicist. One of the 

 ardent champions of Hutton's theory of con- 

 stant changes taking place in the earth's crust. 

 With Lyell, he conceived that the changes on 

 the surface of the earth have always been the 

 same in degree as well as in kind. Modern 

 physicists do not accept this. 



Pliny (Caius Plinius Secundus), i, 265. Born 

 at Como, Italy, 23 A.D. ; died in the eruption of 

 Vesuvius, 79 A.D. Celebrated Roman naturalist. 

 He wrote his famous work on "Natural His- 

 tory" while campaigning as a soldier of the 

 Roman Empire. It is a vast work in which 

 some four thousand works are either cited or 

 quoted from. In the history of scientific princi- 

 ples it may be virtually disregarded, but it is 

 important in the history of the promulgation of 

 knowledge. 



Polybius, i, 201. Born at Megalopolis, Arca- 

 dia, Greece, 204 B.C. ; died about 125 B.C. Cele- 

 brated Greek historian. It is through his wri- 



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