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XL VI. Account of an improved Form of Apparatus for exhi- 

 biting M. Clement Desormes's Experiments on Currents of 

 Air, Sfc. By Robert Younge, Esq.* 



HPHIS improvement consists in the application of moveable 

 * pins on the plate, which enable the operator to vary the 

 size of his discs ; and it is presumed involves the explanation 

 of these phenomena. The form of the glass tube permits the 

 effect to be very distinctly seen, particularly when the current 

 is powerful, the edge of the plate being on a level with the 

 sight. 



AB is a bent glass tube about six inches long ; C is a circular 

 copper plate, having a tube of the same metal attached under- 

 neath, which receives the end of the glass tube B. 



D are upright moveable pins f, passing through holes in 

 the plate, which are represented in the circular drawing. At 

 E the plate is perforated, to form a communication between 

 the upper side of the plate and the glass tube J. 



By commencing with a large disc, and gradually reducing 

 its diameter, we may perceive corresponding alterations in the 

 force of the resistance which it offers ; and by striking circles 

 of different diameters round the central opening, and leaving 

 three or more smaller holes in each circle for inserting the 

 pins, we may easily apply discs of any diameter ; and when 

 these bear a certain proportion to the diameter of the central 

 opening, they are invariably blown off. 



In No. 2. of the Journal of Science, p. 473, it is observed, 

 " If the issue for the vapour be turned towards the earth, 

 and the disc consequently tend to fall, as well by its own 

 weight, as by the pressure of the vapour, still it will not de- 

 scend." Might not the amount of this counter-attraction, or 

 overcoming of gravity, be pretty accurately estimated by the 

 application of a series of discs, of different weights, varying 

 according to the diameter of the opening, and weighted in pro- 

 portion to the power of the current ? 



* Communicated by the Author. 



\ The sole use of these pins is to keep the discs over the central opening. 

 X This apparatus was exhibited at the last meeting of the Sheffield Li- 

 terary and Philosophical Society. 



XL VII. Of 



