These thermometers, made by Mr Adie of Edinburgh, were sunk in the ground at Trevandrum, in lat 8° 30′ 35″, to depths of 3, 6, and 12 French feet. Mr Caldecott says,—“I send you herewith the readings of my long thermometers, which, from various causes, I was not able to put into the ground until the 1st of last May (1842). These two months' readings, therefore, will not, of course, have the proper temperature at the respective depths, especially as it has been raining more or less nearly ever since. Still, I think they will surprise you, as being (so far as they go) entirely opposed to Kupffer's opinion, that the superficial temperature of the earth within the tropics is below that of the air, and to Boussingault's assertion, as to the invariability of the temperature one foot below the surface.