STE 



STE 



than in the latter direction, so that they 

 may be said to progress with occasional 

 retrogradalions. The end of each kind 

 of motion and the beginning of the next 

 is performed with such extreme slow- 

 ness, that for several days together the 

 planet does not seem to change its place 

 among the stars at all, whence it is said 

 to be stationary, i. e. so far as we can 

 trace its motion. 



STATI'STICS. That department of 

 political science which relates to the 

 investigating and the arranging of facts 

 illustrative of the actual condition and 

 resources of a state. It is the basis 

 upon which the statesman and the poli- 

 tical economist reason, and from which 

 they draw conclusions. 



Medical statistics consists in the ap- 

 plication of numbers to illustrate the 

 natural history of men in health and 

 disease. 



STAU'ROLITE {cravpb^, a cross, \i- 



$ot, a stone). Staurotide. A bisilicate 



of alumina and of oxide of iron, called 



also granatite and cross-stone, among the 



specimens of which are the fine mackled 



. crystals from Britany, and the modifica- 



I tions of the simple crystals from St. 



f Gothard, accompanied by prisms of dis- 



thene, perfectly similar to those of the 



staurolite, and sometimes longitudinally 



grown together with them. 



STEAM. The vapour of water raised 



to a high degree of elasticity by heat. 



ft When raised at the ordinary tempera- 



m 4ure, it is termed low-pressure steam; 



f when heat is applied to ordinary steam, 



under a constant bulk, its elasticity 



rapidly increases, and it is then termed 



high-pressure steam. 



STEAM ENGINE. There are two 

 kinds of steam engine in general use, 

 the low-pressure and the high-pressure 

 engine. See Steam. 



1. The term lovj-pressure engine is not 

 in all cases correct, for many of these 

 engines, particularly those which com- 

 bine expansion with condensation, work 

 with a considerable load on the safety- 

 valve, as in the case of the Cornish 

 engines. But the term condensing engine 

 always , conveys a true impression, viz. 

 that the engine is provided with a con- 

 densing apparatus. 



2. The terms high-pressure engine and 

 non-condensing engine are equally sig- 

 nificant: such engines, having no con- 



\ densing apparatus for the production of a 

 vacuum, are obliged to work with steam 

 of higher jjressure than that of the atmo- 

 315 



sphere. The essential parts of a high- 

 pressure engine are only two in number, 

 the boiler and the cylinder; the low- 

 pressure engine requires the presence of 

 a third part, the condenser. 



3. Classification of Engines. The fol- 

 lowing classification of the various steam 

 engines, according to the prmciples by 

 which they are worked, may be found 

 convenient as a table of reference : 



I. Condensing Steam Engines. 



1. Simple condensation in the cylinder. 



Atmospheric engines. 



2. Simple condensation in the condenser. 



1. Watt's single-acting engines. 



2. Watt's double-acting engines. 



3. Cornish single-acting engines. 



3. Condensation and expansion. 



1. Expansion in one cylinder. 



1. Watt's engines, single and double. 



2. Cornish engines, single and double. 



2. Expansion in two cylinders. 



Hornblower's and Woolf s engines. 



II. N on- condensing Steam Engines. 



1. Simple generation of steam. 



2. Generation and expansion of steam. 

 STE'ARIC ACID (o-reap, suet). An 



acid procured from animal and vegetable 

 fats, and from the bile of many animals. 

 Stearine is a solid crystallizable sub- 

 stance, the essential part of all kinds of 

 suet. Stearopten is the solid portion of a 

 volatile oil, as distinguished from elaop- 

 ten, or the liquid portion. 



STE'ATITE {areap, suet). Another 

 name for soapstone, derived from its 

 greasy feel. It may easily be cut with a 

 knife, and yields even to impressions of 

 the nail. The most remarkable varieties 

 are, that of a yellowish-green colour from 

 Greenland, and that from Gbpfersgriin 

 in Baireuth, with small crystals of other 

 mineral substances, especially quartz, 

 converted into, and forming part of, the 

 massive steatite ; a variety called chalk 

 of JBriangon, &c. 



STEEL. Carburetted iron; the aver- 

 age proportion of carbon is supposed to 

 amount to -^^ part. The difl^erent tem- 

 pers, or degrees of hardness, of rigidity, 

 or of elasticity of steel are given by* 

 means of the different degrees of heat tof 

 which the metal is exposed in the opera- 1 

 tion. ->a^*~.--..w I 



STE EL- YARD. The steel-yard differs 

 from the balance, in having its support 

 near one end, instead of in the middle; 

 and also in having the weights suspended 



