514 Mr. W. Sutherland on the Viscosity 



so that from each of Hohnan's values of 77/770 we can calculate 

 a value of 0, which is now given. 



Temp. C 



V/Vo 



... 



14° 



43° 



67-8° 



88-8° 



99-2° 



124-4° 



1-0377 



1-1180 



1-1850 



1-2411 



1-2698 



1-3306 



88 



104 



111 



114 



118 



116 



There appears to be a tendency for the values of C to 

 increase with the temperature-interval ; but it is of no 

 importance, because the smaller temperature-intervals are too 

 small to give a reliable measure of C. Giving each of the 

 values of C a weight in proportion to the temperature- 

 interval from which it is derived, we get the mean value of C 

 as 113. With this value of C in the theoretical equation, the 

 following values of 77/770 have been calculated for comparison 

 with Hohnan's experimental results : — 



Temp. C 14° 



Exper 1-038 



Calcul 1-040 



The agreement is within the limits of experimental error. 



Barus's results for air are now given with the values of C 

 derived from them : — 



43° 



67-8° 



88-8° 



99-2° 



124-4° 



1-118 



1-185 



1-241 



1-270 



1-331 



1-120 



1-186 



1-241 



1-267 



1-329 



Temp.C... 



. 442° 



565° 



569° 



592° 



982° 



995° 



1210° 



1216° 



V/Vo 



. 1-991 



2-083 



2-149 



2-117 



2-711 



2-693 



3-214 



3-147 







. 118 



84 



101 



83 



99 



93 



118 



107 



The range in the values of C is about the same as in 

 Holinau's experiments, but the mean value is less, namely 

 100, but in this mean the values at certain temperatures get 

 undue weight ; and seeing that the measurement of tempera- 

 ture is the most difficult part of the experiment, it would be 

 fairer to take for instance the mean of 84 and 101 at 565° 

 and 569° as 92 at 567°, and in this way to get the values 118, 

 92, 83, 96, 118, and 107, of which the mean is 102. But to 

 compare theory with experiment we will retain the value 

 113 already found from Hohnan's results. 



Temp. 0.... 442° 565° 569° 592° 982° 995° 1210° 1216° 

 Exper. ... 1-991 2 083 2-149 2-117 2-711 2-693 3-214 3-147 

 Calcul 1-976 2-183 2-190 2225 2-781 2"799 3*179 3185 



It is evident, from a comparison of the experimental 

 numbers among themselves, that the agreement between 

 theory and experiment is within the limit of experimental 

 error in these difficult experiments, and the theoretical law is 



