622 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



quite so regular as they were in some other cases. This was probably 

 due to haviog taken observations to be userl without having given suffi- 

 cient training to the fibre. But there can be no serious error involved 

 in the corrected decrement (probably not more tlian 0.1 per cent) as the 

 correction is necessarily Small. 



The pressure in this case, as in the last, was also observed to be 

 sliglitly different when the sphere was used from that when the lead dis-k 

 was used. But by the same method as that used in the case of the tem- 

 perature the correction was found to be negligible. 



As the time for the lead disk was 41.755, no correction for time was 

 necessary. 



Table III is a summary of the data obtained from this experiment. 



TABLE III. 



From the data given in this table 



^jgo.e = 0.0001790, 



and /io = 0.0001716. 



The value of /x has been determined also for pressures less than atmos- 

 pheric. The following tables give the results obtained : — 



TABLE IV. /.=: ,36.034 cm. 



From the data given here, 



/,j5o.6= 0.0001782, 

 and ^0 = 0.0001709. 



