210 Prof. Silas W. Holuian on the Effect of 



less weight than those of the fifth series for air, that they are 

 given here merely as a satisfactory and important check upon 

 the further results of that series. The equation deduced from 

 this latter series I regard as best representing my measure- 

 ments on dry air. It will be noticed, on comparing the two 

 series, that the greatest deviation of the two series is at 100°, 

 where it amounts to less than 0*4 per cent. 



Measurements 1 and 2 were taken during preliminary trials 

 of the apparatus. In 3 to 8 the first capillary was in boiling- 

 water, the second in ice, this reversal of the usual sequence 

 of temperature being made in order to test the apparatus. 

 The mean of these five measurements (the sixth having been 

 rejected when made as having been taken before the static 

 condition of the process was reached) gives 



y= Vm. = 1-267 + a.d. 0*002. 



Vo ~ 



The above equation gives for £ = 99°*94, 



2i =1-2666; 

 Vo 



and the direct observation made, as were all those from which 

 the equation is derived, with the first capillary at 0°, gives as 

 the mean at 9 9°- 66 ^ 



' ^=1-2666. 

 Vo 



The close agreement of these numbers seems to indicate a 

 freedom from constant error of any considerable magnitude 

 in the value of K, and in the expansion-correction to this value. 



Fifth Series. April 1880. — This series was taken with the 

 apparatus as described at page 200, immediately after the com- 

 pletion of the second series with carbonic acid. The measure- 

 ments were made under as favourable conditions as any of 

 this paper, and are of greater weight than all of the others 

 upon air. The full data for the computation of these results 

 are given in Table III. in such form that a recomputation, in 

 so far as relates to those portions subject to possible modifica- 

 tion of such amount as to materially change the result, may at 

 any time be made. The value of K used was the same as 

 that used for the second series of carbonic acid. 



These measurements may be divided, according to tempera- 

 tures, into six groups, and are very concordant, except that 

 the sixth group shows a deviation of about 0*6 per cent, from 

 the value which the other five groups would indicate at that 

 temperature. There appears to be in this group some con- 

 siderable constant error, due probably to a mistake in the 

 reading of the thermometer, which was a different one from 

 that used in the preceding groups. The deviation is so large 



