THE ROYAL SOCIETY, AND AT THE ROYAL OBSERVATORY, GREENWICH. 575 
By taking the mean of the numbers in each column of differences, we find that the 
temperature of the air at the Apartments of the Royal Society in 
O 
January was higher than at Epping reduced to the same level by . . 1‘3 
February was higher than at Epping reduced to the same level by . 1'2 
March was lower than at Epping reduced to the same level by less than O’l 
April was lower than at Epping reduced to the same level by . . . 1'5 
May was lower than at Epping reduced to the same level by . . . TO 
June was lower than at Epping reduced to the same level by . . . 0‘6 
July was higher than at Epping reduced to the same level by . . . 0*2 
August was lower than at Epping reduced to the same level by . . . . 0'3 
September was lower than at Epping reduced to the same level by . 1‘0 
October was higher than at Epping reduced to the same level by . . 0‘2 
November was higher than at Epping reduced to the same level by . r4 
December was higher than at Epping reduced to the same level by . 1'5 
And the mean temperature of the whole period was nearly of the same value at both 
places. 
Having obtained these results, and finding that during the time the sun was 
situated north of the equator the temperature at the Apartments of the Royal Society 
was lower than at Epping, and that it was higher during the time the sun had south 
declination, I requested Mr. Squire to furnish me with full particulars with respect 
to the position of his instrument to the sun and to surrounding objects : the follow- 
ing is the information he gave me : — 
“The thermometer hangs near the north angle of a small projecting pier of a 
wall, nearly close to the brickwork, facing the N.E., and an open country. At the 
back of the wall is a grape-vine, and when in leaf, it so shades the wall that its tem- 
perature is not much affected by the sun’s rays ; but, before the vine is in leaf, it may 
raise the temperature a trifle ; yet from some casual observations scattered over my 
journal as tests, I do not find that the said thermometer is sensibly influenced by the 
heat of the sun at 8 a.m., the time of reading the instrument. On the 13th of May, 
1847, I moved the thermometer a few feet from its former position on the wall, with 
the same aspect, but, at the back of this part of the wall, there is a sort of grotto 
or summer-house, which is covered by thatch and completely interrupts the sun’s rays 
from the wall ; hence its present situation may perhaps be considered more eligible 
for a mean temperature than its former position, but I do not find any difference 
worth notice.” 
The general fact, however, of a higher winter temperature, and of a lower summer 
temperature at the Apartments of the Royal Society, is satisfactorily proved by both 
sets of comparisons, and it is evident that the same cause has been in operation at 
both times, and to the same amount. There can be no doubt that this cause is the 
vicinity of the river Thames to the locality of the observations. 
