OF ARTS AND SCIENCES. 23 



and from oscillating plates the line is Gil from the mean of the 

 equations, 



,, — 0.00018G (1 + 0.0030 t), 

 and ri = 0.000189 (1 -\- 0.002o i), Range 19° to 82°, 



given for different methods of computing one series of data. It is 

 perhaps worthy of remark, that the mean of Meyer's results at 100° 

 agrees with the results of my fifth series within 0.2 per cent. Meyer's 

 observations were made chiefly at two temperatures, and thus, as well 

 as on account of the magnitude of the errors of observation, are in- 

 capable of indicating the small deviation of r]t '• lo ft'O^i the equation 

 of the lirst power of t. 



The observations of Puluj are shown by the lines KL, MN, OP, 

 QR, and ST, of which all but ST are from transpiration experiments, 

 this being by oscillating plates. From the data which I have used 

 in plotting the lines Puluj deduces the first power equations : — 



KL, T, = 0.000179 (1 + 0.0024 t), Range 13°.0 to 27°.0. 



3m, rj = 0.000179 (1 4- 0.0023 t), " 13°.6 to 76°.7. 



OP, rj = 0.000181 (1 -f 0.0022 t), " l°.l to 77".4. 



QR, 7/ = 0.000180 (1 -[- 0.0021 t), " V.b to 92°.7. 



ST, T} = constant (0.03855 + 0.00010213 <) " — 3°.0 to 25°.0. 



From the plots on Plate II., and from others which I have made, it 

 appears to me that the data shown in KL cannot be represented by 

 a straight line, nor are they to be relied upon for giving the rate of 

 change of rj, : tjq at all, the curvature of the line KL which approxi- 

 mately represents the data being undoubtedly the result of uncorrected 

 constant error. The points of the line MJV show an upward con- 

 vexity of slight amount ; those of the line OP are so irregularly 

 distributed as to conceal any slight systematic deviation from the 

 straight line. The points of QR are also very irregularly distrib- 

 uted, but are unquestionably more nearly represented by the line 

 QR, which I have drawn approximately through them, than ])y the 

 straight line SR^, which corresponds to the equation given by Puluj, 

 or by any other straight line. The line QR should certainly be con- 

 vex upwards. 



The numerous experiments of Oberraayer give almost unquestion- 

 able evidence that even for air the coefficient of viscosity increases 

 at a less rapid rate at higher than at lower temperatures. The line 

 a She represents the mean of results by capillaries "11," "26," and 



