423 MR. G. V. VERNON ON 



XXX, Inquiry into the question, Whether Excess or De- 

 ficiency of Temperature during part of the year is usually 

 compensated during the remainder of the same year ? 

 By G. V. Vernon, Esq., F.R.A.S., M.B.M.S. 



Read before the Physical and Mathematical Section, January 7th, 1864. 



A THEORY having recently been promulgated, that excess 

 or deficiency of temperature during some of the months of 

 any particular year is usually compensated by a corre- 

 sponding deficiency or excess during the remainder of the 

 same year, the subjoined investigation has been under- 

 taken in order to see what are the facts during a long 

 period of years. 



The observations of mean temperature made use of are 

 those given by Mr. Glaisher for Greenwich Observatory 

 from 1 77 1 to 1849, published in the Philosophical Trans- 

 actions for 1850 ; and, in addition, the values from 1850 

 to 1862 are those given in the Greenwich Observations. 

 This series embraces in all 92 years, and is the only trust- 

 worthy series for so long a period to be found in this 

 country. The method of investigation has been as fol- 

 lows : — The mean temperature of each month has been com- 

 pared with its average for the entire period, and its dificr- 

 ence from the mean found; in this manner we obtain 

 twelve values for each year, part positive and part negative. 

 The positive values are added together, also the negative 

 ones, and the two amounts thus obtained are given in 

 columns 2 and 3 of Table I. appended to this paper. We 

 thus get two amounts, which tolerably represent the re- 

 lative proportions of the mean temperature above or below 

 the average during each year. In columns 4 and 5 the 

 excess or deficiency of the positive or negative values in 

 columns 2 and 3 are given, the amount being placed in the 



