8 
MR. J. W. CAPSTICK ON THE RATIO OF THE SPECIFIC HEATS 
possible, for these injure the sharpness of the figures very much, and make them 
difficult to measure. 
Covering’ one quarter the length of this tube is a slightly wider one, EC. The 
joint at C was first made according to Kundt’s directions, by wrapping a strip of 
thin india-rubber many times round, and wiring it down, but this proved very 
unreliable. It requires a great deal of care to make such a joint even approximately 
tight, and it is continually getting leaky and requiring to be patched up with india- 
rubber solution, so, finally, I had made a wide tube with thick walls of the best soft 
rubber, and on slipping this on and wiring it down a perfectly tight joint was made. 
The same rubber tube was used for connecting CE with the semi-circular copper 
tube EE, thus making a flexible joint and preventing the conduction of the sound 
through the walls of the tube 
Fig, 1. 
To gas 
holder 
The tube EG, in which the dust figures are made, is 125 centims. long, and 
26 millims. in internal diameter. At the end, E, a brass union is fixed on with 
sealing-wax, and by screwing up tightly the two brass faces with a lead washer 
between, a joint is made tlmt is air-tight, but can easily be taken apart to measure 
the figures and put in fresh dust. At the other end, G, is a similarly detachable cap 
bearing a stuffing box. Through this passes a narrow brass tube with a disc on the 
end, G, by means of which the vibrating length of the column of air can be varied, so 
as to give the best figures. 
Eor apparatus such as this, lead glass seems to be much better than soft German. 
It is impossible to put on the caps without some strain, and with the German glass 
much trouble was caused by the tubes breaking at awkward times and wasting 
precious gas. Since lead glass has been put in, there have been no breakages. 
Through the tube H connection can be made with either a Topler mercury pump 
