APPENDIX AA. 317 



Archimedes's discoveries were, strictly speaking, the starting- 

 point of physics, but Galileo immensely extended the area of the 

 science by connecting isolated facts with general principles, and by 

 founding dynamics. To Aristotle we owe the scientific method of 

 studying the phenomena of nature, namely, observation, experiment, 

 and induction what is, in fact, called the inductive method. 



It is scarcely necessary to add that science has been revolutionised 

 by the discoveries made in physics in modern times, and that 

 humanity is indebted to them for the increased prosperity it now 

 enjoys. 



Barology (^apor, weight, or pdpeiv, to weigh down), the science of 

 weight (gravity) in solids, liquids, and gases. The study of gravity 

 in liquids is subdivided into four branches : 



Hydrostatics (v8a>p ) water), the science of equilibrium of liquids 

 and of the pressure they exert, whether within their own mass or on 

 the sides of the vessels in which they are contained ; 



Hydrodynamics is that branch of physics which considers the 

 motion of liquids ; 



Hydraulics considers the application of liquid motion to machinery, 

 and the application of mechanical force to procure required motion 

 in liquids; in other words, hydraulics is the application of the 

 principles of hydrostatics to conducting and raising water in 

 pipes ; 



Hydromechanics is concerned with the energy of machinery in 

 its application to fluids. 



Thermology (0f'p/*7, heat), the science of heat, the phenomena of 

 which are, next to those of gravity, the most universal in the 

 economy of the world. Heat is the chief antagonist of gravity. 

 Gravity presides over the geometrical and mechanical action of 

 bodies, while heat relates either to the state of aggregation or the 

 composition of molecules. Gravity tends to agglomerate bodies, 

 heat tends to disintegrate or separate them. The application of 

 heat constitutes the chief action of man upon nature. 



The study of heat is quite modern, since it was the great 

 discovery of Black (at the end of last century) which imparted to it a 

 scientific character. 



Acoustics (aKovfiv, to hear) is the science which considers the 

 phenomena of sound. 



