222 Mr. G. F. Rodwell on the Effects 



short distance into the water ; but if we make such an arrange- 

 ment that we have a vessel perpetually emptying itself by a long 

 tube, air enters by the conical cavity, is detached from the apex 

 of the cone, and passes down the tube with the descending water. 



In order to determine the amount of air carried down by this 

 means, I fitted a small funnel N, fig. 1, into the upper orifice of 

 the tube JB, and placed the delivery-tube H in such a position 

 that the water which it delivered impinged against the side of 

 the funnel. This being the case, a hollow cone of water possess- 

 ing rapid rotatory motion was formed in the funnel, and air 

 entered through its centre : the air and water on issuing from 

 the funnel formed alternate disks in the tube B, and these rapidly 

 descended into the vessel A. A mercury gauge communicating 

 with the interior of A showed that the pressure remained per- 

 fectly constant, and precisely the same amount of air came over 

 during a number of successive experiments. 



The amount of air carried down was very large : when the 

 circular delivery-tube /^ths of an inch diameter (used in some 

 of the previous experiments) was employed, no less than 1200 

 cubic centims. of air were carried down by half a litre of water, 

 the water-surface in A being 1 inch below the orifice of B.(viz. 

 at b, fig. 1). The flow from the delivery-tube was = half a litre 

 of water in 24 seconds. 



With the smaller circular delivery-tube, y^^ths °f an mcn 

 diameter, and delivering half a litre of water in 39 seconds, 1392 

 cubic centims. of air were carried down by half a litre of water ; 

 the water-surface in A being, as before, 1 inch below the orifice 

 of B. Stated in other words, a little stream of water, about 

 Y^th of an inch in diameter at the orifice from which it issues, 

 with a head of water of 2 feet, carries down in one hour 128 

 litres of air. By this method we see, therefore, that 1 part of 

 water carries down more than 2f times its own bulk of air — 

 the largest quantity which I have found under any circumstances 

 to be carried down by water. 



The mouth of the funnel N was covered air-tight with a thick 

 sheet of caoutchouc, and a small vibrating tongue, such as is used 

 in Wheatstone's concertinas, was fitted into the caoutchouc ; the 

 delivery-tube was then passed through the cover, and so placed 

 that it delivered water, as before, against the side of the funnel : 

 when water flowed, the tongue was readily vibrated by the enter- 

 ing air. A second tongue was now added, and it was found that 

 the flow from the delivery-tube might be diminished from half 

 a litre of water in 24 seconds to the same quantity in 40 seconds, 

 and yet the tongues were readily vibrated. 



A musical instrument might thus be constructed in which the 

 air could be twice used before leaving the instrument; for the 



