178 Experiments en the lateral Communkation of Motion in Fluids, 



Experiment IX. i. The orifice P (fig. i) through a thin plate is circular, and 18 lines in 

 diameter. The charge of fluid above the centre of the orifice is 40 inches. Four cubic feet 

 of water were emitted in 38 feconds. 



2. To the orifice P, fig. i, I applied the tube A C D, fig. 4, the upper end of which A C 

 had the form of the contratSted vein. The diameter at A was 18 lines in length, AD 31 

 inches, and the fituation of the tube horizontal. The expenditure of four cubical feet was 

 made in 48 feconds. 



3. The fame orifice and the fame tube were applied to the horizontal bottom of the re- 

 ■fervoir fig. 7, fo that the tube was vertical, and A C = 40 inches, or the height of the charo-c 

 in the two former experiments. The four cubic feet flowed out in 48 feconds, as in the 

 fecond experiment. 



Experiment X. The laft defcribed experiment was repeated with a circular aperture of 

 li,2 lines in diameter. The extremity A C, of the tube fig. 4, had the form of the con- 

 tra£ted vein ; the end A having the fame diameter as that of the orifice. The other cir- 

 cumftances were as in the preceding cafes. In the difpofition, according to the firft cafe 

 four cubical feet of water flowed out in 98 feconds j in the fecond cafe the time was 130 

 feconds ; and in the third cafe 129 feconds. 



In each of thefe two experiments the tubes and the expence of water were the fame for 

 the fecond and the third cafes ; whence it follows, that the force by which the expenditure 

 was governed was the fame in both cafes. Now the force which a£ts in the fecond cafe is the 

 fame as in the firfl ; and confequently the fame force likewife zCts in the firfl and third cafes. 

 All the difference of the refult between the firft cafe and the two following arifes from the 

 retardation produced by the inequalities of the internal furface of the tubes. 



Experiment XI. The height A B, fig. 7, being conflantly 32,5 inches, and the orifice B O 

 1 8 lines in diameter, the tube B O C Q_was applied to the orifice itfelf, the fuperior extremity 

 of this tube having the form of the contrafted vein. When the length of the tube was varied, 

 the times of the efflux of four cubic feet of water were as in the following table. 



The fifth column of this table is calculated from the proportion of retardation produced by 

 the irregularities of the internal furface of the tubes. Citizen BofTut has obferved, that thefe 

 retardations* increafe rather in a lefs ratio than the velocity of the flream. This is perhaps 

 the reafon of the difference obferved between the fourth and fifth columns. 



Experiment XII. I applied to the orifice P, fig. i, the fame tubes as in the foregoing expe- 

 riment one after another in an horizontal fituation, the height of the charge being conftant- 



* Hydrodyn. Art. bit. 



