580 MR. GLAISHER ON THE THERMOMETRICAL OBSERVATIONS TAKEN AT 
By taking* the means of the numbers in each column of differences, we find that 
the temperature of the air at the Apartments of the Royal Society was 
O 
Higher than at the Royal Observatory, Greenwich, in January by . . 1*6 
Higher than at the Royal Observatory, Greenwich, in February by . 1*4 
Higher than at the Royal Observatory, Greenwich, in March by . . 1*1 
Higher than at the Royal Observatory, Greenwich, in April by . . . 1*1 
Higher than at the Royal Observatory, Greenwich, in May by . . . 1*1 
Higher than at the Royal Observatory, Greenwich, in June by . . . 0*9 
Higher than at the Royal Observatory, Greenwich, in July by . . . 1*0 
Higher than at the Royal Observatory, Greenwich, in August by . . 1*3 
Higher than at the Royal Observatory, Greenwich, in September by . 1*1 
Higher than at the Royal Observatory, Greenwich, in October by . . 1*3 
Higher than at the Royal Observatory, Greenwich, in November by . 1*3 
Higher than at the Royal Observatory, Greenwich, in December by . 1*4 
And upon the whole year the excess of temperature at Somerset House was 1°*2 ; and 
to reduce readings taken at Somerset House to those at Greenwich, it is necessary to 
subtract the preceding numbers from them ; and it is necessary to increase the read- 
ings of the Royal Observatory by the above numbers to make them comparable with 
those taken at the Royal Society. 
One part of these differences is owing to the difference of elevation, and which will 
amount to about 0°*3 ; the greater part of the remaining difference is most probably 
owing to the vicinity of the water of the Thames, whose temperature during the night 
hours, at all seasons of the year, is several degrees higher than that of the air (see 
remarks following Table XIII.). 
The general result of the preceding investigations, with respect to the temperatures 
of London and the country is, that those parts of London situated near the river 
Thames, are somewhat warmer upon the whole year than the country, but that those 
parts of London which are situated at some distance from the river, do not enjoy 
higher temperatures than those due to their latitudes. 
I proceed now to reduce the results at Somerset House to those of the Royal Ob- 
servatory, Greenwich, by applying the numbers following the preceding Table to the 
numbers in Table I. of my former paper, and to those in Table X. till the year 1840. 
After this date the numbers are extracted from the several volumes of the Greenwich 
Meteorological Observations. 
