[ 6. I 



fiderable ; but not fe'nfibly augmented, when the velocity was 

 much diminifhed. Since the dilatation of the vein in this cafe de- 

 pends on the velocity with which the water iffues from the aperture, 

 it is to be inferred, that it is caufed by the refiftance of the air, 

 which producing a retardation of the preceding particles, thofc 

 which follow impinge againft them, and the thicknefs of the 

 vein is encrcafed; for the fame reafon as when the jette.is made 

 perpendicularly upwards, a broad head is formed in confeqvience 

 of the retardation of the uppermoft particles. Now fince it ap- 

 pears, that the dilatation of the vein which arifes either from the 

 different diredlions of the particles, or the refiftance which they 

 undergo from the air, or both together, cannot account for the- 

 difference of diftance to which the particles are projected on an 

 horizontal plane, we muft conclude that this difference is caufed 

 by the different velocities with which they efcape from the; 

 orifice; 



When a tube m?irs (fig. 3 ) is inferted into the veffel A BCD,' 

 it is found, that the velocity is increafed nearly in the fub-duplicate- 

 ratio of the length of the pipe, when the tubes are fhort ; and 

 that it approaches nearer to that fub-duplicate ratio, according as 

 the length of the pipe is increafed. To account for this increafc 

 of velocity has appeared a matter of fome difficulty, fince the 

 water cannot iilue at r J- with a greater velocity than it enters at 

 mtz; and it does not appear how ihe velocity at mn can be en- 

 creafed by inferting a tube beneath it. In- order to explain the 



caufe 



