BIOGRAPHICAL INDEX 



pletely discarded the pre-existing "ideas" or 

 "forms" of Plato. His "System of Logic" is the 

 basis of that used at the present day. He was 

 for three years the tutor of Alexander the Great. 



Arkwright, Sir Richard, ix, 17. Born at 

 Preston, England, Dec. 23, 1732; died at Crom- 

 ford, Derbyshire, England, Aug. 3, 1792. In- 

 vented the cotton-spinning frame, or "water- 

 frame," a device that revolutionized spinning. 

 He began life as a barber, and his early inven- 

 tions were made in leisure hours when not work- 

 ing at his trade. He amassed an enormous for- 

 tune as a result of his invention, and in 1786 was 

 knighted by George III. 



Arnold of Villanova, ii, 34. Born cir. 1240; 

 died in 1313. Nationality unknown. A physi- 

 cian, alchemist, and astrologer, who taught at 

 Paris, Barcelona, and Montpellier. He has been 

 incorrectly credited with the discovery of hydro- 

 chloric, nitric, and sulphuric acids. These were 

 certainly known before his time. 



Arrhenius, Svante. Born at Upsala, 1859. 

 Swedish physical chemist, professor in the Uni- 

 versity of Stockholm. His theory of electrolytic 

 dissociation, which he has established, is one of 

 the most important of recent contributions to 

 science. It is that if a current is passed through 

 a substance whose aqueous solution is capable of 

 conducting electricity, it is broken up in solu- 

 tion into parts of the composing elements 

 charged, some with positive and others with 

 negative electricity. The existence of positive 

 and negative "ions" has explained a number of 

 chemical phenomena hitherto incomprehensible. 



Arzachel, ii, 16. Born in Spain, cir. 1050. 

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