1813.] 



Nevj Hi/drauUc Machines, 



183 



Article VI. 



Report respecting various Hydraulic Machines, presented to the 

 Imperial Institute of France, hy M. Mannoury Dectot. 



Paris, Dec. 30, 1812. 



The Perpetual Secretary for the Sciences certifies that what 

 follows is an extract of the proces-verhal of the sitting of Monday 

 the 28th December, 1812. 



M. Mannoury Dectot has submitted to the Class several 

 hydraulic machines of his own invention, respecting which M. 

 de Prony, M. Perier, and myself, were charged with making a 

 report. 



We will acknowledge that ten new machines proposed all at 

 once by the same person, who had likewise announced several 

 more which were soon to follow the former, filled us at first 

 with some suspicion, knowing how much trouble and labour it 

 costs even the most ingenious artists to invent a single machine, 

 possessed of some remarkable or useful properties. 



But this suspicion was unjust, and was soon succeeded by that 

 pleasure which we always feel on discovering a mind as exact in 

 its assertions as fertile in its resources. 



The principles of mechanics in general, and of hydrodyna- 

 mics in particular, have been long known. Every body must be 

 aware that what is called an invention in them can be only a new 

 combination of general principles. We know further that in 

 hydrodynamics especially, the subject is so complicated for the 

 calculus, that it is generally impossible to know a priori what 

 will be precisely the effect of such or such a combination ; so 

 that experiment is absolutely necessary to confirm or destroy 

 those results which seemed to follow from theory. 



M. Mannoury has neither spared trouble nor expense to 

 remove in this respect all doubts. The commissioners have been 

 witnesses of his numerous experiments, and in consequence have 

 been able to give that sanction to his discoveries which can alone 

 place theDi in the number of certain and positive facts. 



The general problem which M, Mannoury proposed to himself 

 is this : a fall of water being giveiiy io elevate a portion of that 

 fluid above the reservoir, by means of a machine all the parts of 

 which are absolutely fixed j and which of course neither contains 

 levers, nor v/heels, nor pistons, nor valves, nor any other move- 

 able part. 



One is much inclined at first to consider this problem as 

 impossible, and we do not know that it has been undertaken, or 

 at least solved, by any person. In fact, a reflection immediately 

 presents itself, which seems to destroy all hope ; namely, that if 

 such a machine were possible^ it would probably occur acci-^ 



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