358 SECTION MECHANICS. 



energy residing in the stream ; in order that the water may pass away 

 from the turbine in an inert condition, and that in acting upon the 

 vanes of the turbine eddies may not be formed, and that thus energy 

 may not be wasted. 



There are probably few sights more surprising to the old-fashioned 

 millwright who has been used to see water-wheels of fifty or even seventy 

 feet diameter, employed for the utilization of a high fall, than that of 

 a turbine occupying only a few cubic feet of space, but running at such a 

 velocity as to consume the whole of the water of a considerable stream, 

 and so to consume it as to deliver nearly as large a percentage of 

 useful effect as would the cumbrous water-wheel itself. 



If a fall of water be employed with the mere object of raising water, 

 this end can be attained without the employment of either water- 

 wheel or turbine by the aid of the Montgolfier ram, a very useful 

 machine for those cases wherein but a small percentage of the whole 

 fall is required to be raised, but is required to be raised to a consider- 

 able height. No. 1996, which I have before me, is a glass model of 

 such a ram, but I fear it is too small to be visible, except to those who 

 are very near to the table. You are, however, all aware that the prin- 

 ciple of action consists in the sudden arrestation of a column of water 

 flowing with a velocity due to the head. When the water is arrested, 

 a small portion of it raises an outlet valve, and thereby passes 

 into an air vessel against a pressure competent to drive the water 

 up to the desired height, while the main body recoils along the 

 supply pipe ; then an escape valve having fallen open the water 

 that has recoiled returns, a large portion passes out by this valve, and 

 then the velocity being once more fully established, the escape valve 

 shuts and causes another arrcsiation and a repetition of the working. 

 This is an implement by which a large volume of water, and having 

 but a low fall, can be made to raise a portion of itself to a great 

 height ; but there is a converse use of water, wherein the employment 

 of a small stream moving rapidly owing to its having descended iron) 

 a considerable height, is caused to induce a current in other water, 

 and to draw it along with itself with a diminished velocity, but with 

 a velocity still competent to raise the united stream to the insignificant 

 height which suffices for delivering the water from swamps and marshy 

 land. 



