OE INTERNAL PEICTION OF AIR AND OTHER GASES. 



265 



and compared with the results of observation. The calculated sums of the decrements 

 are given in the last column. 



Table IV. shows the results of the twelve experiments with the fifth arrangement. 

 They are arranged in groups according to the pressure of the air, and it will be seen 

 that the observed values of L are as independent of the pressure as the calculated values, 

 in which the pressure is taken into account only in calculating the value of x in the 

 fifth column. By arranging the values of L— L' in order of temperature, it was found 

 that within the range of atmospheric temperature during the course of the experiments 

 the relation between the viscosity of air and its temperature does not perceptibly differ 

 from that assumed in the calculation. Finally, the experiments were arranged in order 

 of time, to determine whether the viscosity of the wire increased during the experiments, 

 as it did when steam was first used to heat the apparatus. There did not appear any 

 decided indication of any alteration in the wke. 



Table V. gives the resultant value of (x in terms of the different units which are em- 

 ployed in scientific measurements. 



Note, added February 6, 1866. — In the calculation of the results of the experiments, 

 I made use of an erroneous value of the moment of inertia of the disks and axis= 1-012 

 of the true value, as determined by six series of experiments with four suspension wires 

 and two kinds of auxiliary weights. The numbers in the coefficients of m in Table IV. 

 are therefore all too large, and the value of ^ is also too large in the same proportion, 

 and should be 



(«,= -00001492(461°+^). 



The same error ran through all the absolute values in other parts of the paper as sent 

 in to the Royal Society, but to save trouble to the reader I have corrected them where 

 they occur. 



Table I. — Experiment 62. Arrangement 5. Dry air at pressure 0-55 inch. 

 Temperature 68° F. May 9, 1865. 



The observations were continued in the same way till five sets of readings of this kind 

 were obtained. The following were the results. 



MDCCCLXVL 2 



