TECHNICAL INDEX AND GLOSSARY 



Histology. The science that deals with the minute structure 

 of animal and vegetable tissues. This science depends very 

 largely upon the microscope, and has developed chiefly since 

 that instrument was perfected. See "Lister and the Perfected 

 Microscope," Vol. IV, p. 109. 



Horse Power. The unit of work, as applied by Watt to the 

 steam engine. Watt assumed that a horse could perform an 

 amount of labor equivalent to the raising of 33,000 pounds to 

 the height of one foot in one minute; this was doubtless an over- 

 estimate, but it has remained the standard. See Vol. VI, p. 60. 



Hot-air Engine. An engine in which heated air is used instead 

 of steam or exploded gas to propel the piston. See "Gas and 

 Oil Engines," Vol. VI, p. 132. 



Hydrophobia. See "Rabies" in the present index. 



Hydrostatic Press. An apparatus for transmitting power; it 

 makes use of the principle that pressure applied to a given sur- 

 face of a liquid is transmitted unmodified to each corresponding 

 surface of the enclosing well. In practice a small force applied 

 to a small piston in a cylinder becomes multiplied as transmitted 

 to the large piston of a connecting cylinder. See "Hydraulic 

 Power," Vol. VI, p. 74. 



Hydrostatics. The science that deals with the properties of 

 fluids. For Archimedes's solution of some of the most im- 

 portant problems of hydrostatic equilibrium, see Vol. I, p. 196. 

 For the experiments of Galileo, see "Galileo and the Equilibrium 

 of Fluids," Vol. II, p. 105. 



Hygiene. The science of health; in particular having to do 

 with improvements in living, ventilation, sanitation, etc. See 

 "The Berlin Institute of Hygiene," Vol. V, p. 193. 



Hypnotism. Name given by Dr. Braid to the practice of in- 

 ducing artificial somnambulism in a susceptible subject. The 

 hypnotic condition is subjective, and is indeed by suggestion, not 

 by the giving out of any "magnetic" or other occult influence 

 on the part of the hypnotist. See "Physiological Psychology," 

 Vol. IV, p. 266. 



Inclined Plane. A familiar mechanism through the use of 

 which heavy bodies may be raised to a height with a conserva- 

 tive use of power. Diodorus Siculus records that the Egyptian 

 utilized the principle of the inclined plane in building the pyra- 

 lids. See "Inclined Planes and Derricks," Vol. VI, p. 37. 



Induction, Electric. A curious phenomenon, in which an elec- 



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