532 



EXPEHIMEISTTS AND INQUIRIES 



As the air escaped through the puncture, it 

 was sup[)lied by a phial of known dimensi- 

 ons, at equal intervals of time ; and accord- 

 ing to the frequency of this supply, the ave- 

 rage height of the gage was such as is ex- 

 pressed in the first Table. It appears that the 

 quantity of air, discharged by a given aper- 

 ture, was nearly in the subduphcate ratio of 

 the pressure. The second, third, and fourth 

 Tables show the result of similar experiments 

 made with some variations in the apparatus. 



Tabic I. 



Table in. 



All numbers throughout this paper, where 

 the contrary is not expressed, are to be un- 

 derstood of inches, linear, square, or cubic. 



A is the area, in square inches, of an aper- 

 ture nearly circular. B, the pressure in inches. 

 C, the number of cubic inches discharged in 

 one minute. D, is the observed velocity of 

 the air in a second, expressed in feet. E, the 

 square root of the height of a column of air 

 equivalent to the pressure. F, the quotient of 

 the two last columns. 



Table ii. 



A is the area of the section of a tube about 

 two inches long. B, the pressure. C, the 

 quantity of air discharged in a minute, by es- 

 limation. D, E, and F, as in Table i. 



A is the area of the section of a tube. B,. 

 its length. C, the pressure. D, the discharge 

 in a minute. E, F, and G, as D, E, and F, 

 in Table i. 



Table IV. 



A is the area of an oval aperture, formed 

 by flattening a glass tube at the end : its dia- 

 meters were .025 and .152. B, the pressure. 

 C, the discharge. D, E, and F, as in Table i. 



II. Of the Direction and Velocitif of a Stream 

 of Air. . 



An apparatus was contrived for measuring, 

 by means of a water gage communicating 

 with a reservoir of air, the pressure by which 

 a current was forced from the reservoir 

 through a cylindrical tube; and the gage 

 was so sensible, that, a regular blast being 

 supplied from the lungs, it showed the slight 

 variation produced by every pulsation of the 

 heart. The current of air issuing from the 

 tube was directed downwards, upon a white 

 plate, on which a scale of equal parts was 

 engraved, and which was thinly covered with 

 a coloured liquid ; the breadth of the surface 

 of the plate laid bare was observed at diftier- 

 ent distances from the tube, and with difler- 

 ent degrees of pressure, caie being taken 

 that the liquid should be so shallow as to 



