312 PROCEEDINGS OF THE AMERICAN ACADEMY 



hand, its warmth expels the gas more freely, and when the finger is 

 removed it escapes in a jet, which makes the experiment more de- 

 cisive. 



" In making the following experiments three persons were usually- 

 employed ; one to keep up a uniform blast, counting the revolutions 

 of the handle by a watch ; a second to throw the chlorine into the 

 pipe, and also to observe and declare the moment when the blue color 

 appears upon the starched paper ; the third to note upon a watch the 

 interval between these two events. 



" Results of Experiments. 



" 1. Air in motion communicates motion to those portions of air at 

 rest in its immediate vicinity. To this phenomenon Venturi, who 

 discovered and explained it, has given the name of the lateral com- 

 munication of motion in fluids. 



"2. A jet of air falling upon any surface is never reflected, but 

 spreads itself out, and forms a thin layer in immediate contact with 

 that surface. It may be admitted as a principle, that fluids do not, 

 under any velocity or any angle of incidence, possess the property of 

 reflection, like solids, and it is, doubtless, owing to the absence of this 

 property that they adhere to bodies against which they strike. In vir- 

 tue of this adhesion, a jet of fluid striking a sphere perpendicularly to 

 its surface spreads itself uniformly over both the superior and inferior 

 hemispheres ; a similar jet striking a horizontal cylinder perpendicu- 

 larly to its surface completely surrounds it, and does not leave it until 

 the two parts of the jet meet on its inferior border and form one com- 

 mon sheet. (Savart, Annales de Chimie et de Physique, Tom. LIV.) 



" When a jet of water strikes a truncated cone perpendicularly to its 

 axis, and just above its lower base, it spreads out, covering more than 

 half its surface, and, rising upward, leaves its upper base in a continu- 

 ous sheet, vertically in a plane nearly coinciding in direction with that 

 of the sides of the cone, and horizontally nearly in the direction of 

 tangents to the surface of the cone, while a small portion only of the 

 fluid forms two small streams, which drop down from those two points 

 of the lower base of the cone which are at right angles with the orig- 

 inal direction of the jet. 



" When a jet meets a circular plane at its centre and perpendicular- 

 ly, it forms a thin continuous sheet over the whole surface. Both the 

 direction and continuity of this sheet are preserved far beyond the 



