Memoir of M. D' Aubuisson Oe Voisins. 217 



employed amoug the Pyrenees, and named trompes, in which 

 water alone, by falling rapidly into a vertical canal, hollowed 

 out in the trunk of a tree, draws up the air and forces it back 

 again. In 1825, he placed an air-pipe, 400 metres in length, 

 in the mines of Rancie. In the eyes of any other engineer, 

 probably, this would have been merely an artificial ventilation, 

 necessary in piercing a great subterranean gallery ; but, in 

 his view, the field was enlarged ; this became a new branch 

 of bydrodynamics, not previously developed or experimented 

 upon ; it was a new means of promoting science in one of its 

 most valuable applications. He could not, however, discern 

 all the future bearings of this principle ; he could not foresee, 

 for example, that one day, perhaps, atmospheric propulsion 

 on railroads might give a more extended application to the 

 modest experiments of E,ancie, and a more direct bearing on 

 the intei'ests of mankind. Tliis is the grand privilege of 

 scientific works, that their power acknowledges neither time 

 nor space ; they are strengthened by what weakens every- 

 thing else. 



The erection of this long air-pipe was, therefore, the occa- 

 sion of a numerous series of experiments, made in concert 

 with the engineer M. Marrot, and which related to the gene- 

 ral value of the pressure and expenditure of air at the ex- 

 tremity of a pipe, considering its length, diameter, and the 

 pressure at the entrance ; to the variations which these values 

 undergo, whether by the effect of sudden bends, or by ter- 

 minating the pipe by orifices in their walls of various diame- 

 ters, or by conical tubes more or less resembling the buses 

 of blowing-machines, &c., &c. These experiments furnish re- 

 sults valuable at once by the simplicity of their form, and the 

 precision of tlieir practical application, asM. D'Aubuisson has 

 himself proved, by applying them numerically to a consider- 

 able number of machines. He has published all these inves- 

 tigations in a detached form in the Annals of Mines, year 

 1826, and following years, and at a later period he gave a 

 short view of them in his Traite Hydraulique. 



The last of these publications appeared in 1829, M. 

 D'Aubuisson had just completed his great undertaking for 

 the distribution of water to the town of Toulouse, to which he 



