I'tO Proceedings of the 



course of the central current. This is exactly the same explana- 

 tion as that given by M. Clement. 



The general effect was first illustrated by the use of some of 

 M. Hachette's small mouth tubes *, and afterwards by a large 

 glass apparatus, into which air \Vas thrown by a pair of forge 

 bellows, and by which discs, from six to eight inches in diameter, 

 were supported in the air, although unsustained from beneath, 

 otherwise than by the causes already described. 



The state of the forces in different directions, relative to a cur- 

 rent of air moving in the atmosphere, was thfen shown : the con- 

 stant force of the pressure of the atmosphere is increased before the 

 current by the added force of the stream of air, but it is diminished 

 at the sides and behind, because the force of the currents is from 

 those parts ; and part of the elasticity which, whilst the air was 

 quiet, was sufficient to oppose the pressure of the atmosphere, and 

 retain all at rest, is now opposed and neutralized by the force of 

 momentum ; consequently the air of the neighbouring parts is 

 urged in from the sides and behind, and made to move with the 

 current. Screens or other light substances interposed in the way 

 of the moving air, show by their direction in which way the air is 

 forced ; and some curious effects may in this way be obtained. 

 Two pasteboard screens, about six inches square, being suspended 

 parallel to each other, at a distance of two or three inches, move 

 towards each other, and seem to attract each other forcibly when a 

 stream of air is blown from the mouth through a small pipe between 

 them. If a screen, having a hole in the middle, be hung about an inch 

 from the end of an open cylinder, and a small pipe be inserted, an 

 inch or two through the hole, but not touching it, into the cylin- 

 der ; immediately that a current of air is blown through the pipe, 

 the screen closes upon the open end of the cylinder, and may 

 actually, by altering the position and continuing the current, be 

 suspended in the air, and sustained against the cylinder ; not by 

 any impulse of the air blown through the pipe against the screen, 

 but solely from the tendency of the air behind the jet to follow the 

 stream. If the jet of a blowpipe be introduced an inch or more 

 into an open tube an inch wide, and four or five inches long, and 

 then, whilst a stream of air is forced through it, the flame of a 

 Candle or lamp be brought to the mouth of the tube behind the jet, 

 the whole of the flame, though a large one, will be forced into the 

 tube, by an entering current of air, which owes its existence 



f See Quarterly Journal, New Series, vol. ii. p. 193. 



