438 ARCHITECHNICS. 



compressive strength of a post, is nearly proportional to the greater 

 side, into the square of the lesser, divided by the square root of the 

 length. A cubic block of wrought iron, each side of which is one 

 inch long, will bear a pressure of about 17,000 Ibs. ; and a like cube 

 of oak, will bear about 5,000 Ibs., before crushing. The transverse 

 strength, of a horizontal beam, is proportional to the breadth, into 

 the square of the depth, divided by the length. The torsive 

 strength, is nearly proportional to the cube of the diameter, divided 

 by the square root of the length. These formulae are only approxi- 

 mations ; and reference should always be had, as far as possible, to 

 experiments on the same materials, and masses of nearly the same 

 dimensions. 



The manufacture of chemical articles, as the alkalies, acids, and 

 various salts ; and the preparation of paints and dye stuffs, on a large 

 scale ; would probably find its most appropriate place, in our ar- 

 rangement, as an appendix to Hylurgy. 



CHAPTER II. 



MACHINERY. 



IN the branch of Machinery, we would comprehend the appli- 

 cation of the moving forces used in the arts, such as water, wind, 

 and steam power ; and the construction of machines in general, so 

 far as it may be considered to form a distinct class of arts. The 

 name machine, is of French extraction ; but derived originally from 

 the Greek, pyzavy, having the same signification. The construction 

 and management of machinery, has, at the present day, become so 

 extensive and technical, as, in our opinion, to require its separation 

 from the science of Mechanics, and its location as a distinct branch 

 of the arts ; depending, of course, on the principles of Mechanics 

 and Hylurgy ; with special reference, also, to the objects for which 

 machines are constructed. Although subservient to Civil Engineer- 

 ing, Manufactures, and various other arts, most machines have so 

 much similarity of construction, and are so often compared or con- 

 trasted, that a connected study of them seems necessary to a full 

 course of Technology. 



A machine, may be defined as a structure serving to produce, or 

 to regulate motion ; and to apply it to some special purpose in the 

 arts : the object, in general, being a saving of time, or of force. 

 Machines are applied, for accumulating power, as in the tilt hammer, 

 and pile engine ; for regulating power, as in the fly wheel, and 

 governor ; for increasing the velocity, as in the turning lathe, and 

 carding machine ; for increasing the pressure, or tension, as in the 

 lever, and other simple mechanical powers ; for prolonging the ac- 

 tion of a power, as in the clock, and watch ; for registering opera- 

 tions, as in the gas-meter, and anemometer ; and for performing de- 

 licate operations, more accurately than can be done by the hand alone, 

 as in graduating machines, for dividing scales and circles, or in ma- 



