-.[ 67 ] 



been dlfcliarged according to theory; fo that in long pipes^ the 

 diiFerence between theory and experiment, he fays, was not 

 greater than what mi^ht be expeded from the fridion of the 

 pipe=, and other caufes which may be fuppofed to retard the 

 velocity. When he inferted a pipe of the fame diameter with the 

 aperture, which terminated in a truncated cone fixed ' in the 

 orifice, (fig 4.) he expeded, that the quantity of water difcharged 

 in a given time would have been diminished, becaufe the water, 

 iffuing through the orifice mn, would have room to form the 

 vena contraBa in the enlarging cone-, but he found, that the 

 fame quantity of water was difcharged, as if the pipe had con- 

 tinued throughout of the fame diameter with the orifice. The 

 reafon of this is manifeft from what has been faid, for the preffure 

 of the air will not fuffer the truncated cone to remain partly 

 empty, as it would be if the vena contraBa were formed 5 it 

 will therefore continue full, and confequently the water will 

 pafs through it in the fame manner as if the water in the cone, 

 furrounding the pipe mabn, were congealed. 



Mr. Vince likewife inferted into the bottom of the veflel a 

 perpendicular pipe', in form of a truncated cone, the narrower 

 part being fixed in the orifice ; by which he found the efflux to be 

 encreafed more than if he had inferted a cylindrical pipe of the fame 

 length, whofe diameter was equal to that of the narroweft part 

 of the conical pipe. This effed may be explained on the fame 



\ I, 2 principle 



