MECHANICAL PHILOSOPHY. 103 



metliod or art of pcrforminp; aritlimetical operations by 

 means of little square rods, called Napier's bones. 



Spherics. — The doctrine of the sphere; the science of the 

 properties and relations of the circles, figures, and other 

 niatrnitudes of a sphere, produced by planes intersecting it. 



Stereom'etry (Gr. stereos, solid, and victrco, I measure). — That 

 part of jicometry which teaches the art of ineasuring solids 

 or ascertaining the solid contents of bodies. 



Survey'ing'. — The art of determining tlie area of any portion 

 of the earth's surfl\ce, the lengths and directions of the 

 boundary-lines, the contour of the surface, etc., with an 

 accurate delineation of the whole on paper. 



Trigoiiom'etry (Gr. trigOnon, a triangle, and metreo, I measure). 

 — The science of determining the sides and angles of 

 triangles by means of certain parts which are given. 



Mechanics, 



Statics, 



Dynamics, 



Hydrodynamics, )■ See Mechanical Philosophy. 



Hydrostatics, 



Hydraulics, 



Pneumatics. 



MECHANICAL PHILOSOPHY. 



Mechanics (Gr. mcchane, a machine). — That branch of prac- 

 tical science which treats of the eifects of powers or motive 

 forces, and their action on bodies, either directly or by 

 means of machines and engines. 



Aerodynam'ics (Gr. aer, air, and diDiamis, power). — The 

 science which treats of the motion of the <iir and its me- 

 chanical effects when in motion ; also its resistance to bodies 

 moving in it. 



Aerostatics (Gr. acr, air, and stafos, sustaining). — Treats of 

 the cqiti/ibrium of elastic Jlaids, or of bodies sustained in 

 them. 



Barol'ogy (Gr. haros, weight, and logos, a discourse). — The 

 science of weight, or of the gravity of bodies. 



Dynamics (Gr. dnnamis, power). — Treats of bodies in motion. 



Hydraulics (Gr. hudOr, water, and aulas, a pipe). — That 

 branch of hydrodynamics which teaches how to estimate 

 the velocity of moving inelastic fluids. It is this im- 



