PROFESSOR FORBES ON THE CLIMATE OF EDINBURGH. 339 
Taste V. (continued.) 
1844 35°77 February 1795-6 37°80 November 
1810 3671 February 1835 37°88 January 
1819 36°6 February 1821 38°29 January 
1807 36°8 Feb. and March 1824-5 38°42 December 
1798 37:09 January 1845-6 38°77 December 
{ 1849 37:09 January 1822 39:05 January 
1836 37°15 February 1832 39°13 January 
1823-4 37°32 December 1828 39°45 January 
1840 37:47 February 1833-4 40°30 December 

40. Thus it appears that out of fifty-six winters, the lowest monthly mean 
temperature occurred twenty-seven times in January, fifteen times in December, 
ten and a half times* in February, twice in November (in 1795 and 1807), and 
one and a half times in March (in 1807 and 1837).+ 
41. Ill. The Epoch of Highest Temperature mainly determines the earliness or 
lateness of the season. It is well known that in these latitudes the mean epochs 
of greatest heat and cold are, on a long average of years, nearly six months apart. | 
But in any given year, the fluctuations of temperature in winter are so irregular, 
as to make it very difficult to define the inferior culmination of the curve of 
temperature. I employ, therefore, the position of the maximum, as deciding 
the character of the season with respect to earliness or lateness. This has been 
approximately determined by a very simple process of approximation, which I 
used in my paper on the Temperature of the Earth at Different Depths.§ The rule 
is as follows :—“ Calling A the excess of the mean temperature of the hottest 
month above the preceding month, B the excess of the mean temperature of the 
hottest above the following month; Then 15 Se is the number of days + 
that the hottest day of the year {Wc the 15th day of the hottest month.” 
42. The results of this (merely approximate) estimate will be given in a future 
table (see Table IX. col. 5, below). In the meantime, the following is the classi- 
fication of the seasons, as early or late. The earliest date was June 22d in 1845, 
the latest August 14th in 1795. 
* When the temperature of February and March was the same, as in 1807, then one-half is 
the proportion for each. 
+ Mr Guatsuer’s numbers for Greenwich would give for a like number of years, January 30, 
December 15, February 10, March 1, November 0. ; 
{ See Qurreret on the Climate of Brussels, and § 6 of the present paper. 
§ Edin. Trans., vol. xvi. p. 216. 
VOL. XXII. PART II. As 
