On Machines in General. 295 



" I now proceed, in conformity with your suggestion, 

 to make a brief recapitulation of the most material parts of 

 this paper, and to endeavour to enumerate, and to place in 

 one point of view, those articles recommended above, which 

 appear to me to be best calculated to answer the desired 

 purpose : 



" Caustic potash, train oil, waste salt, mixture of salt 

 and oil, urine, oil of hartshorn, linseed oil, sea water, as- 

 safoetida, chaff and refuse oil. 



*' Any of these, in my opinion, might be employed wiih 

 perfect safety to the revenue. 



'* 1 have the honour to be, gentlemen, 



** your faithful and obedient humble servant, 



*' Samuel Parkes." 

 — »'• 



JJII. Essaij upon Machines in General. By M. Carnot, 

 Memler of the French Institute, &c. &c. 



[Continued from p. 2?S.] 



LV. X HESE reflections should seem sufficient for unde- 

 ceiving those who think, that with machines charged with 

 levers arranged mysteriously, we may put an agent, though 

 never so feeble, in a condition to produce the greatest effects : 

 the error proceeds from persuading ourselves, that it is pos- 

 sible to apply to machines in movement what is not true 

 except with respect to the case of equilibrium : from the 

 circumstance of a small power holding a very great weight 

 in equilibrium, many persons think that it could in the same 

 way raise this weicht as quickly as they please : now this is a 

 very striking mistake, because, in order to succeed, the agent 

 must procure for itself a velocity beyond its faculties, or 

 which would at least make it lose so much the greater part 

 of its effort upon the machine as it would be obliged to 

 move itself more quickly. In the first case the agent has no 

 other object to attain than to make an effort capable of 

 counterbalancing the weight; in the second case, besides 

 this effort, there must be also another to overcome the iner- 

 tia, both of the body on which it impresses the movement 

 and of its own proper mass : the total effort which in the 



T 4 first 



