Wonder if these were biting their fingernails down to the elbows,
THE HOT WEDNESDAY OF 1808
Farmers, and others engaged in outdoor pursuits, men of science, and others engaged in observations on meteorological phenomena, have much reason to doubt whether the reported temperatures of past years are worthy of reliance. In looking through the old journals and magazines, degrees of winter cold and summer heat are found recorded, which, to say the best of it, need to be received with much caution; seeing that the sources of fallacy were numerous. There was one particular Wednesday in 1808, for instance, which was marked by so high a temperature, as to obtain for itself the name of the 'Hot Wednesday;' there is no doubt the heat was great, even if its degree were overstated.
At Hayes, in Middlesex, two thermometers, the one made by Ramsden, and the other by Cary, were observed at noon, and were found to record 90° F. in the shade. Men of middle age at that time, called to mind the 'Hot Tuesday' of 1790, which, however, was several degrees below the temperature of this particular Wednesday. Remembering that the average heat, winter and summer, of the West Indies, is about 82°, it is not surprising that men fainted, and horses and other animals died under the pressure of a temperature so unusual in England as 8° above this amount. In the shade, at an open window looking into St. James's Park, a temperature of 94° was observed. In a shop-window, on the shady side of the Strand, a thermometer marked 101°; but this was under the influence of conducted and radiant warmth from surrounding objects.
At Gainsborough, in Lincolnshire, two thermometers, made by Nairne and Blunt respectively, hanging in the shade with a northern aspect, marked 94° at one o'clock on the day in question. In the corresponding month of 1825, observers were surprised to find a temperature of 85° marked in the quadrangle of the Royal Exchange at four o'clock in the 19th, 86½° at one o'clock on the same day, 87° at Paris, and 91° at Hull; but all these were below the indications noticed, or alleged to be noticed, in 1808.
It is now known, however, better than it was in those days, that numerous precautions are necessary to the obtainment of reliable observations on temperature. The height from the ground, the nature and state of the ground, the direction in reference to the points of the compass, the vicinity of other objects, the nature of those objects as heat-reflectors, the covered or uncovered state of the space overhead—all affect the degree to which the mercury in the tube of a thermometer will be expanded by heat: even if the graduation of the tube be reliable, which is seldom the case, except in high-priced instruments. On this account all the old newspaper statements on such matters must be received with caution, though there is no reason to doubt that the Hot Wednesday of 1808 was really a very formidable day.