Temperature on the Viscosity of Gases, 219 



cordance between the results of various observers. It should 

 be borne in mind, however, that some of the lines are plotted 

 from means, some from single observations, and others from 

 equations deduced either by the observers or by myself. 

 The individual points, therefore, must not be used without 

 qualification as a measure of the precision of the results 

 obtained by any single observer. 



Carbonic Acid, C0 2 . 



The curve OA on Plate I. is from the equation deduced at 

 page 215 for my own results. There can be no question as to 

 the decided curvature shown being far beyond the limits 

 of variable experimental error. My computations have also 

 shown that the third power of the temperature in the linear 

 equation was necessary. The experimental means are marked 

 along the curve. 



The curve D B is from an equation of the same form 

 7j = Vo (1+A^ + B* 2 ), 



in which A and B are computed from the results of A. von 

 Obermayer * with capillary " I." The term C* 3 was omitted 

 because of the smaller number of points and their somewhat 

 less precision. That the line represents approximately the 

 data will be seen from noting the distribution about it of the 

 observed points. The curvature is here also undoubted, 

 although Obermayer merely remarks that " it follows from 

 these experiments with some probability that the increase in 

 coefficient of friction with rising temperature is less at higher 

 than at lower temperatures." A comparison of this curve 

 with mine shows that Obermayer's results and my own are 

 in substantial agreement as to the rate of change in b, 

 the curvature of the two lines being very nearly the same. 

 Indeed, if my results be thrown into the same equation, using 

 only the first and second powers of t } the value of B becomes 

 0-00000136, while that from Obermayer's data is B = 

 0-00000137. The value of A from my results is, however, 

 considerably larger than from Obermayer's, so that his value 

 of rj t : t}q at 100° is about 0*7 per cent, below mine, and at 

 200° about 1 per cent, below. The line O C is from the 

 equation 



Vt = Vo (1 + 0-003585*- 0-00000105* 2 ), 

 deduced by me from Obermayer's experiments at the three 

 indicated temperatures with the capillary " D." This is in 

 still closer agreement with mine in numerical values of n : 770, 

 but has slightly less curvature (B = 0-00000105). The value 

 * A. von Obermayer, Wien, Ber. lxxiii. p. 468 (1876). 



