TECHNICAL INDEX AND GLOSSARY 



This fact was not established until late in the eighteenth cen- 

 tury. See "The Function of Respiration," Vol. IV, p. 92. 



Rhodium. A metal belonging to the platinum group, dis- 

 covered by Wollaston in 1804. See "Element" in the present 

 index for chemical symbol and atomic weight. 



Rosetta Stone. A slab of black rock found in Egypt, the in- 

 scriptions on which furnished the key for the decipherment of 

 the Egyptian hieroglyphics. It was discovered in Egypt in 1799, 

 and is now in the British Museum. See "The New Science of 

 Oriental Archaeology," Vol. IV, p. 287. 



Rotary Engine. A type of engine in which rotary motion is 

 obtained direct, without change of direction as in the case of 

 reciprocating engines. The turbine engine is an example of a 

 rotary steam engine. See "Rotary Engines," Vol. VI, p. 119. 



Ruby. A precious stone, rich red in color, a transparent 

 variety of corundum. It can be produced artificially of con- 

 siderable size. See "Gems, Natural and Artificial," Vol. IX, 

 p. 319. 



Saliva. A liquid secreted by the salivary glands of the mouth, 

 containing a digestive ferment. See "Animal Chemistry," Vol. 

 IV, p. 128. 



Sarcode. The name given by Dujardin to the viscid, slimy 

 fluid, capable of motion, found within the cell wall. See "The 

 Cell Theory Elaborated," Vol. IV, p. 122. 



Scandium. One of three then unknown elements, the existence 

 of which were predicted by Mendeleeff on formulating his 

 periodic law. See "Periodicity of Atomic Weights," Vol. IV, 

 p. 64. 



Serum-therapy. A method of treating certain diseases by 

 means of the modified blood serum of man or the lower ani- 

 mals. Behring's diphtheria antitoxine serum, discovered in 1892, 

 is an example. See "Preventive Inoculation," Vol. IV, p. 231, 

 and "Serum-therapy," Vol. IV, p. 240; also, "Aims and Objects 

 of the Pasteur Institute," Vol. V, p. 182. 



Sextant. A portable instrument for measuring the altitudes 

 of heavenly bodies above the horizon, or their angular distance 

 as seen in the sky; hence its use with the chronometer in de- 

 termining exact latitude and longitude. See "The Development 

 of the Sextant," Vol. VII, p. 18. 



Shooting-stars. See Meteorites. 



Signatures, Doctrine of. A mediaeval theory, which in effect 



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