868 



HYDHIODJC ACID 



from one of the plunger-cases ; and when the power is to bo transferred through drift- 

 ways, the pipes are carried down the shaft through the levels to several points where 

 power is required and returned by the same or a second shaft to the second ram-case, 



1202 



forming a circuit or an endless band for transmitting power. See Specification, 

 A.D. 1867, No. 3386. J. D. 



HYDRAULIC PRESS, or the Bramah Press. Mr. Bramah took out his 

 patent in 1796. It rests upon the well-known hydrostatical principle, that when a 

 mass of fluid is in equilibrium, pressure applied at any part of it is transmitted over 

 its whole mass, and each particle sustains the same pressure as every other particle. 

 In its simplest form, it consists of a large piston moving in a water-tight cylinder, 

 the bottom of which is filled with water, which also communicates by tubes 11 lied 

 with water, with the bottom of a cylinder of a small forcing pump. The water in 

 this last is submitted to any pressure we may wish to apply, and that being transmitted 

 to the large piston, lifts it up, moving along with it whatever may bo connected witli 

 it. The apparent gain of power is just in proportion to the difference of areas of tho 

 sections of tho pump, and of tho cylinder. If tho one, for example, have a radius of 

 only one-fourth of an inch, and the others ono of ten inches, the area, being in the 

 proportion of the squares of the linear dimensions, will be as 1 to 1,600; and the 

 apparent gain will bo exactly proportional to this difference. 



HYDRIODIC ACID (Acide hydriodique, Fr. ; Hi/drioJsaure, Ger.) is an acid 

 formed by the combination of 127 parts of iodine with 1 part of hydrogen by weight, 

 and by measure equal volumes of iodine-vapour and hydrogen combined without con- 

 densation. It is obtained pure and in the gaseous state by introducing into a glass 



