836 HYDRAULIC MACHINERY, FOR MINES 



districts, so as to render them accessible for manufacturing purposes, the rapid streams 

 which abound in such localities -will probably become valuable sources of motive 

 power, and a wider field may then be afforded for the application of wator-prossuro 

 engines to natural falls. 



' The object, however, which I have chiefly had in view since I first gave attention 

 to this subject, has been to provide, in substitution of manual labour, a method of 

 working a multiplicity of machines, intermittent in their action, and extending over a 

 large area, by means of transmitted power produced by a steam-engine and accumu- 

 lated at one central point. The common mode of communicating power by shafting 

 could only be applied in cases where the machines were collected within a small 

 compass, and where the accumulation of power necessary to meet varying resistance 

 did not exceed that which a fly-wheel would afford. Compressed or exhausted air 

 was almost equally inapplicable to the purposes I contemplated, in consequence of the 

 many objections which its elasticity involves, as well as the liability to leakage, 

 which, in an extended system of pipes and machines, requiring a multitude of joints, 

 valves, and fitting surfaces, would form an insurmountable difficulty. But the use of 

 water as a medium of transmission is free from all these objections, and its fitness for 

 the purpose intended is now thoroughly established by the results which havo been 

 obtained.' 



HYDRAULIC LIMESTONE. See HYDRAULIC CEMENT. 



HYDRAITI-XC MACHINERY, FOR XKXHTES. The application of a head 

 of water to rotatory and reciprocatory engines, and the use of water in driving wheels, 

 as well as in transmitting power from one point to another, are subjects of considerable 

 importance in mining operations. 



The power of water is derived either from its direct weight, as in the case of 

 pressure-engines, or from its weight and impulse combined, as in overshot and breast- 

 wheels. 



In transmitting power for pumping purposes, advantage is taken of the non-com- 

 pressibility of water, as well as of the facility with which water can be passed 

 through straight or bent pipes. 



Although the weight and incompressibility of water are in many ways advantageous 

 for the purposes of the engineer, yet the use of water in pressure-engines necessitates 

 peculiar mechanical contrivances. The valves have generally to be moved by an 

 arrangement partially independent of the engine, whilst the shock consequent on 

 instantly arresting the flow has to be mitigated by means of an air-vessel, momentum- 

 plunger, or other suitable contrivance. 



In Europe the rain-fall is from two to three feet per annum ; about two-thirds of 

 which is evaporated, the remainder finding its way to the sea. In Australia, where 

 the atmosphere is exceedingly dry, and the rain-fall very much less, there are but few 

 constant streams or rivers. The consideration which should therefore be given to the 

 supply of water, and to the motors to be employed for mining purposes, must mani- 

 festly be governed by the hydrographic circumstances of different countries. But in 

 lands where rain is tolerably frequent and abundant, the following remarks will admit 

 of general application: (1.) Mountainous countries, with a large extent of upper 

 watershed, will furnish a tolerably constant volume of water, at a high fall, both for 

 driving pressure-engines and turbines. (2.) Hilly localities much below the line of 

 watershed will afford volume of water at a lesser fall, suitable for pressure-engines, 

 turbines, and overshot wheels. (3.) A flat undulating country, with an extensive 

 back-watershed, will frequently afford volume of water available as power through 

 the medium of breast, undershot wheels, and low-fall turbines. (4.) Hilly localities 

 near to the top of watersheds can only furnish an intermittent supply of water at 

 comparatively low falls, and that to extend the use of water as power in such 

 situations, store-dams will be requisite. 



As the hydraulic engineer requires facts, data, and rules for his guidance, those 

 deemed of practical importance will be given as concisely as possible. 



Constitution of Water. 



By weight By measure 



: : : S| J 



100-0 3 



Density of Water. One cubic inch at 62, the barometer being at 30 inches, woi<rhs 

 252,458 grains, or water is 830 times heavier than atmospheric air. A cubic foot 

 weighs 1,000 ounces, or 62 Ibs. 



Expansion. Water expands one-ninth of its bulk in freezing, and decreases in 



