Tll.VNSACTIONS OF SECTION G. 



867 



■ efBciency of So per cent., ■which it is fully expected, fi-dui resalta obtained from an 

 experimental machine moo'.-ed in the tidewayof the Thames, will be the case, the 

 theoretical horse-power of the stream and that developed by the motor at various 

 velocities would be approximately as under : — 



It Is obvious fi-om this table that the cost per horse-power depends almost 

 entirely upon the velocity of the curi-ent, as the capital outlay, attendance, &c., 

 would be nearly constant. It should also be observed that where considerable 

 power is required the motors can be placed iu series at near intervals, and the cost 

 of attendance further reduced. 



In deciding: whether any particular stream or estuary is suitable for the use of 

 this motor with advantage, as compared with heat engines, it should be remarked 

 that most available figures referring to the working cost of these engines are based 

 upon a day of ten hours, whereas the water motor can be worked with very little 

 attention, ever^ in a tideway, for a greater number of hours, and in a river 

 perpetually. 



4. On the E,v''ended Use of the Principle of the Hiidraullc Earn. 

 Bij H. D. Peausall, Assoc. Mem. Inst. C.E. 



The hydraulic ram is a machine of extreme simplicity which enables the po-wer 

 of a fall of water to be used directly to raise water to any desired height, and it is 

 the only known means of doing this directly, all other means being more or less 

 roundabout and complicated, being a combination of at least two machines, 

 involving a double transformation of power. This simple machine has therefore 

 many very great advantages over any alternative methods, but, notwithstanding 

 this, -we find that one hundred years after its invention the older methods are still 

 iu use where the quantity t)f water dealt with is large. 



The author investigates the reason of this, and shows that it is chioflv due to 

 an imperfect realisation of the principle of the machine. The paper also gives an 

 account of an investigation of the hydraulic ram by the author and of soma 

 engines constructed in accordance with this investigation, which prove tliat 

 engines on the principle of the hydraulic ram may be advantageously used for the 

 largest water powers, such as waterworks for town supply, irrigation. Sec. 

 Similar engines are also remarkably serviceable in compressing air, giving in this 

 case results so far exceeding any hitherto obtained that they vitally atfect the 

 important question of transmission of power to a distance. 



The ordinary hydraulic ram, as designed by Montgolfier and as still made, is 

 then described. 



The violence which accompanies the action of these machines is the first and 

 most obvious reason against their application to large quantities of water, and has 

 given currency to the idea, which the author found to be prevalent, that, as 

 commonly stated, such machines ' acted by a blow.' 



This is shown to be a mistake by reference to the elementary dynamic law 

 that any body in motion can be stopped by any resistance, however small, if it. 

 continues to act through sutlicieiit distance ; from which it follows that thi proper 

 action is not ' by a blow," but by a continued motion of the water against a steady 

 resistance. 



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