VI. An account of the heat of July, 1825; together with some remarks upon sensible cold

Abstract

As I think it may not improbably be deemed an object of some curiosity to the Royal Society to collect from different parts, an account of the very unusual heat of last July, I presume to offer the enclosed report of observations which I made at that time, at Datchet, in Buckinghamshire, with every precaution that suggested itself to me, to ascertain the real temperature of the atmosphere, uninfluenced by adven­titious circumstances. The observations were made with a small sensible thermometer, which had been carefully graduated. On Friday July 15, the wind blowing from the south-west, the thermometer was suspended in the shade of a large laburnum on my lawn, at a height of about five feet and a half from the ground. This tree was chosen, as admitting the air in some degree to pass through it, at a time when the wind and the sun were both in the same quarter. On the subsequent days, the wind being in the east and north-east, the thermometer was hung, at about the same height, from an external branch of a very thick Portugal laurel, standing likewise upon the lawn, at a distance from any building; where it was exposed to the full influence of the wind, and at the same time effectually sheltered either from the actual rays of the sun, or from any object heated by it. I have been the more particular in giving this account, because it is often difficult, especially in great, or rapid changes of tem­perature, to get observations made with sufficient attention to avoid the neighbourhood of buildings, or other objects, which may considerably affect the thermometer, and give an appearance of heat sometimes greater, sometimes less than the truth.