OF OBSERVATIONS FOR TEMPERATUII C . 



23 



ture in each month at Port Kennedy, we find an anomaly in the table of results 

 in April, May, and Juno, 1859, when the symmetry of the observing hours is 

 interrupted by observations being taken at 5 A. M. and 11 P. M. To remedy 

 this defect, I have first established an approximate equation of the diurnal varia- 

 tion, and, by means of it, computed the difference between the mean at 4 h and 5'', 

 and also between ll h and 12 u . These differences were applied respectively to the 

 mean for -V' and to the mean for IP, which gave the deduced means for P' and 12 h . 

 The maximum corrections for diurnal effect of the annual change occur at mid- 

 night, and are as follows: — 



fn January 

 I't bruary 

 March 



April . 

 .May . 

 June . 



0°.00 

 —0.15 

 —0.26 



— 0.32 

 —0.30 

 —0.22 



AtO' 

 zero; 



A. M., the corrections are the same with the sign reversed; at noon, they are 

 at intermediate hours, proportional values were applied. The monthly mean 

 is left unchanged (or very nearly so). 



For August, I have combined the means of August, 1858 and 1859. 

 Accordingly, we have the following table of the diurnal variation of the tem- 

 perature for each month of the year : — 



For the purpose of making full use of all the bi-hourly observations, it was 

 thought advisable to express the values for the months of April, May, June, and 

 August, September, October, analytically, and to supply by interpolation values 

 for the hours 2, 6, 10, A. M and P. M. The values thus computed were derived 

 from the following expressions, in which the angle d counts from midnight, and is 

 reckoned at the rate of 15° an hour : — 



For April, * = — 2°.54 + 3°67 sin (o + 255°) + 0°.T0 sin (20 + 27°) 



" May, t= +15.16 + 4.09 sin (0 + 255 ) + 0.24 sin (28 + 257 ) 



" June, t = +35.17 + 4. 05 sin (e + 267 ) + 0.90 sin (28 + 181 ) 



For August, t = +35°.57 + 1°.32 sin (0 + 228°) + 0°.18 sin (28 + 142°) 



" September, I = +25.47 + 1.39 sin (8 + 213 ) + 0.31 sin (28 + 55 ) 

 " October, t = + 7.59 + 0.77 sin (e + 258 ) + 0.35 sin (28 + 80 ) 



