734 a 
_ Respecting the last table Mr. Everest says, the irregularities in 
the temperatures may be explained by some of the wells being worked 
for the purposes of irrigation, and:therefore supplied by a current of 
fresh water continually issuing from the ground ; whilst in those wells 
which were still, the surface of stagnant water exposed to the air was 
cooled by the evaporation dependent on so dry a climate. 
The general level of the country is said to be 800 feet above the 
sea, and the temperature of Delhi, as determined by the author from 
observations made during four years, to be 75°°78, or 74°°64 Fahr., 
taken as the mean between that result and another (73°°5) given in 
the’ « Gleanings of Science.’ If to this 1°-8 were added for the depth 
of the wells (115 feet), according to the rule which holds good in 
Europe, the temperature would be 76°44, or something less than 
that obtained by observation. Mr. Everest then proceeds to show, 
according to the formula of Mr. Atkinson*, that the temperature 
at. the level of the sea, in the latitude of Delhi (28° 40’), should be 
77°84 (74°64 + 3°-2 for the difference of 800 feet of altitude), and 
that the temperature of Sincapore, in the second degree of north 
latitude, is 80°°2, leaving, in comparison with that of the former 
locality, only 2°56 of temperature for above 26° of latitude. ‘This 
discrepancy, he is of opinion, may be partly explained by Sincapore 
being surrounded by the sea contiguous to the Pacific and Indian 
Oceans, and cooled by perpetual showers, and Delhi being in the 
midst of dry and burning plains. But, adds the author, the mean 
annual temperature of Cairo, in 30° north Jatitude, and situated in 
a dry and sandy continent, is not above 72°'5, leaving consequently 
yet a difference to be accounted for, and which he conceives may be 
owing to the tropical rains being limited west of the Indus to 232° 
north latitude, but extending in India even beyond 30° of latitude. 
During the period in which the rain prevails, or from the 25th of June 
to the 15th of September, the south-west monsoon blows nearly from 
the equator and transports a large quantity of aqueous vapour ha- 
ving)a temperature from 77° to 81°, or that of the rain as it falls 
and soaks into the earth, the evaporation being then very trifling. 
The quantity of rain during the other nine months is so small that 
it cannot counteract this effect, which, Mr. Everest says, may ac- 
count both for the high temperature of the surface, and for the tem- 
perature of the interior being greater than was to be expected. 
If this explanation be allowed, the author observes, it may easily 
be conceived that when a much greater portion of the globe was 
covered with water,.and the evaporating surface consequently larger, 
currents of air charged with aqueous vapour prevailed still more, 
and modified the ancient climate even in still higher latitudes. 
In conclusion, Mr. Everest remarks, that Scandinavia presents 
another instance of the carrying power of fluids with respect to heat, 
the coast, and even the bays, being free from ice to the latitude of 
71°, owing probably to a south-westerly current in the adjacent 
ocean; and he states, on the authority of persons who have win- 
* Transactions of the Astronomical Society for 1826, vol. ii. p. 137 et seq. 
