i}<jo Theory and EJfeci of the TVatei'-blowihg Machiiw. 



air being lefs heavy than the water, occupies the upper part of the receiver, whence being 

 urged through the upper pipe O, it is conveyed to the forge. 



Experiment 25. I formed one of thefe artificial blowing engines of a fmall fize. Tlie 

 pipe B D was two inches in diameter, and four feet in heiglit. When the water accurately 

 filled the fediion B C, and all the lateral openings of the pipe B D E C were clofed, the pipe 

 O no longer offered any wind. 



It is, therefore, evident that in the open pipes the whole of the wind comes from the atmo- 

 fphere, and no portion is afforded by the decompofition of water. Water cannot be decompofed, 

 and transformed into gas, by the fimple agitation and mechanical percuffion of its parts. The 

 opinion of Fabri and Dietrich have no foundation in nature, and are contrary to experiment. 



It remains, therefore, to determine the circumftances proper to drive into the receiver, 

 M N, the greatefl quantity of air, and to meafure that quantity. The circumftances which 

 favour the moft abundant produdlion of wind, are the following. 



It is known that in the parabola, ii d xhe. affumed as conftant, d y will decreafe in the 



ratio of The feparation of the balls in fig. 15. is more rapid in the upper fpaces of 



V X 



the fall than in the lower. In order, therefore, to obtain the greateft effeft from the acce- 

 leration of gravity, it is neceffary that the water fhould begin to fall at B C, fig. 16. with tlie 

 leaft poflible velocity ; and that the height of the water F B Ihould be no more than is ne* 

 ccffary to fill the fedion B C. I fuppofc the vertical velocity of this fediion to be produced 

 by an height or head equal to B^ C. 



2. We do not yet know, by direct experiment, the diiiance to which the lateral com- 

 munication of motion between water aud air can extend itfelf ; but we may admit with con- 

 fidence, that it can take place in a fedion double that of the original fettion, with which 

 the water enters the pipe. l.et us fuppofe the fedion of tlie pipe B D E C to be double the 

 feflion of the water at B C ; and in order that the ftream of fluid may extend and divide 

 itfelf through the whole double fedlion of the pipe, fome bars, or a grate, are placed in 

 B C, to diftribute aud fcatter the water through the whole internal part of tlie pipe. 



3. Since tlie air is required to move in the pipe O with a certain velocity, it muft be 

 comprefl^ed in the receiver. This compreffion will be proportioned to the fum of the acce- 

 lerations, which fhall have been dcflroyed in the inferior part K D of the pipe. Taking 

 K D= 1,5 feet, we Qiall have a preffure fufficient to give the requlfite velocity in the pipe 

 O. The fides of the portion K D^ as well as thofe of the receiver M N, mull be exaiftly 

 clofed in every part. 



4. The lateral openings in the remaining part of the pipe B K, may be fo difpofed and mul- 

 tiplied, particularly at the upper part, that the air may have free accefs within the tube. I 

 will fuppofe them to be fuch that 0,1 foot height of water might be fulEcient to give the 

 jieceflary velocity to the air at its introduction through the apertures. 



All thefe conditions being attended to, and fuppofing the pipe B D to be cylindrical, it is 

 required to determine the quantity of air which pafles in a given time through the circular 

 fcaion K L. Let us take in fett K 6=1,5; 1^ C=B F=a; IB D=^. By the common 

 theory of falling bodies, the velocity in K L will be '],']6V{a + b — 1,4); the circular fec- 

 feoii K L = 0,7 850'. Admitting that tlic air in K L to have acquired the fame velocity as 



the 



