222 Royal Society : — Messrs* Stewart and Tait on the 



Again, let us suppose that (A)— (B) denotes the gas-effect for -fo in., 

 and we obtain 



Dry hydrogen. Dry air. Dry carbonic acid. 



Gas-effect at ¥ 6 F 4-0 20*0 18-0 



Finally, let us regard as unknown residual effect the difference 

 between the whole effect and the gas-effect, and we obtain 



Dry hydrogen. Dry air. Dry carbonic acid. 



Eesidual effect 5-5 5-0 6-0 



35. Similar experiments with the same galvanometer were made 

 with a disk of cartridge-paper, of which the pores were filled 

 with solid paraffin. And here we may mention that in all experi- 

 ments with paper disks a small wooden attachment was placed at 

 some little distance behind the disk and at the height of the pile, 

 and against this the disk was pressed during tapping — care being 

 taken that the disk did not touch it during motion, but only when 

 it was pressed against it by bringing up the pile. 



With this paper disk the amount and speed of motion were repre- 

 sented by 30 turns of the handle, or 3750 turns of the disk, in 30 

 seconds. The results were as follows, a result representing on an 

 average somewhat less than four rotations : — 



Pressure of 



Heat-indication for 



in inches. Dry hydrogen. Dry air. Dry carbonic acid. 



(A) ,& 27-0 55-0 55-0 



(B) Jj>. 23-0 35-0 32-0 



Treating these results in the same manner as those of the ebonite- 

 disk, we obtain : — 



Dry hydrogen. Dry air. Dry carbonic acid. 

 Whole effect (<&).. 25-0 45-0 43-5 

 Gas-effect (^-) .... 4-0 20-0 23-0 

 Eesidual effect .... 21-0 25*0 20-5 



36. Now, if we suppose that there is only one effect due to 

 gas, it follows : — 



(a) That the proportion between the effects due to the various 

 gases experimented on (and all of the same pressure) is neverthe- 

 less different for the two disks. 



((d) That the proportion (for the same disk) between the effects 

 due to the various gases experimented on is different according to 

 the pressure. 



If, however, we suppose that there are two effects, one of which 

 is independent of the residual gas, we find : — 



(a) That, as regards the gas-effect, the proportion between that 

 due to the various gases is nearly the same for both disks. Thus 

 in the ebonite disk we have 4, 20, 18, while in the paper disk we 

 have 4, 20, 23 as representing the gas-effect for the various gases. 



(/3) That the residual effect in either disk is nearly the same for 

 the various gases. Thus in the ebonite disk we have 5'5, 5-0, 6-0, 

 while in the paper disk we have 21*0, 25*0, 20-5 as representing the 

 residual effect for the various gases. 



