TECHNICAL INDEX AND GLOSSARY 



nitric tcid and of nitre. See "Nitrogen from the Air," Vol. VI. 

 P- 303. 



Nitrogen. A gaseous, non-metallic element, constituting 77 

 per cent by weight, or four-fifths by bulk, of the earth's atmos- 

 phere. Discovered by Henry Cavendish about 1809. See "Henry 

 Cavendish," Vol. IV, p. 13; and "Nitrogen from the Air," Vol. 

 VI, p. 303. 



Nuclei of Plant Cells. The component part of the vegetable 

 cell, first recognized by Robert Brown in 1833. See "Robert 

 Brown and the Cell Nucleus," Vol. IV, p. 115. 



Oil Engines. See "Gas and Oil Engines," Vol. VI, p. 132. 



Organic Evolution. The changes in living organisms, the out- 

 growth of which is their present forms. See "Theories of 

 Organic Evolution," Vol. IV, p. 140. 



Organic Matter. The term applied to animal and vegetable 

 matter as distinguishing it from mineral, or inorganic, matter. 



Organicists' System. A system of medicine in vogue during 

 the eighteenth century, the followers of which did not believe 

 that life was due to some spiritual entity, but rather to the 

 structure of the body itself. See "Animists, Vitalists, and 

 Organicists," Vol. IV, p. 184. 



Oxygen. A non-metallic gaseous element, discovered in 1774 

 by Joseph Priestley, and called by him "dephlogisticated air." 

 Later Lavoisier gave it the name oxygen (chemical symbol O). 

 See "Joseph Priestley," Vol. IV, p. 18. 



Paint. Colors or dyes mixed with some vehicle, such as oil, 

 turpentine, water, etc., so as to spread over a surface and retain 

 their brilliancy after drying. See "Paints, Dyes, and Varnishes," 

 Vol. VIII, p. 258. 



Paleontology. The science of ancient life that inhabited the 

 earth during the ages previous to historic times. The science 

 originated early in the nineteenth century and was named by 

 de Blainville and Fischer von Waldheim in 1834. See "The 

 New Science of Paleontology," Vol. Ill, p. 74. 



Palladium. A metal resembling platinum, used in the manu- 

 facture of certain scientific instruments. It was discovered by 

 Wollaston in 1803. See "Element" of the present index. 



Paper. A material composed of vegetable fibers formed 

 artificially into thin sheets. It came into use about the twelfth 

 century in Europe, but was probably known and used long 



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