o 



[ 66 ] 



it is fo fliort, as not to be fufficient to give the particles a vertical 

 diredlion. All which agrees very well with the experiincrHs made 

 by the ingenious Mr. Vince, of which he has given us an account 

 in the Phil. Tranf. for the year 1795. Thus he tells us, that 

 having inferted a tube, a quarter of an inch in length, into a 

 cylindrical veffel 12 inches deep, he found that the velocity did 

 not fcnfibly differ from that through the orifice ; the caufe of 

 which he difcovered to be this, that the flream did not fill the 

 pipe, but that the fluid was contraded, as when it flowed through 

 the fimple orifice. When the pipe was half an inch long, inferted 

 into a vefTcl of the fame depth as before, the velocity of the water 

 from the pipe and from the orifice, which ought by theory to 

 have been as v/12,5 ^° v^i2, or as 49 to 48, was by experiment 

 found to be nearly in the proportion of 4 to 3. Now if che ratio 

 of 49 to 48 be increafed in the ratio of 7 to 6, (becaufe this is the 

 ratio of the diminution of the velocity on account of the con- 

 tradlion of the vein, and this contradlion either nearly or entirely 

 vanifhes in a pipe,) we fhall have the ratio of 3,57 to 3. When 

 the pipe was an inch long, the velocity from the pipe and from 

 the orifice, which, according to theory, ought to have been as 

 v/13 to ^/\^^ or as 26 to 25, appeared by experiment, very nearly 

 in the ratio of 4 to 3 ; now if the ratio of 26 to 25 be encreafed 

 in the ratio of 7 to 6, we fhall have the ratio of ,3,64 to 3. When 

 he made ufe of longer pipes, the velocity of the efHuent water 

 by experiment approached nearer to that which ought to have 



been 



