VOL. LXXIV.] PHILOSOPHICAL TRANSACTIONS. 60Q 



XXXII. Experiments to Investigate the Variation of Local Heat. By James 



Six, Esq. p. 428. 



To investigate the variation of local heat, I made the following experiments. 

 On Sept. 4, 1783, I placed thermometers in 3 different stations; one on the top 

 of the high tower of Canterbury cathedral, about 220 feet from the ground; 

 another at the bottom of the same tower, at about 1 10 feet ; and a 3d in my own 

 garden,* not more than 6 feet from the ground. They were all carefully exposed 

 to the open air in a shady northern aspect; the lowest was as little liable to be 

 affected by the reflection of the sun's rays as the elevation would permit, the 2d 

 still less, and the highest not at all. They thus remained in their several places, 

 where I visited them daily for 3 weeks, and minuted down the greatest degree of 

 heat and cold that happened each day and night in their respective stations, by a 

 peculiar thermometer. 



By these observations it appears that, notwithstanding some irregularities, the 

 heat of the days at the lowest station always exceeded that at the middle, and 

 still more the heat at the upper station. As in many instances the higher regions 

 of the atmosphere have been found to be colder than the lower, and the ther- 

 mometer in the garden was more liable to be heated by the reflection of the sun's 

 rays from the earth than the upper ones, a difference of this kind might have 

 been expected. But I was greatly surprized to find the cold of the night at the 

 lowest, not only equal to, but very frequently exceeding the cold at the higher 

 stations. As I wished to know, whether these variations would continue the 

 same in the winter, when the weather was colder; and whether a thermometer, 

 placed at some distance from the city, having an elevation equal to that on the 

 top of the cathedral tower, would agree with it; on Dec. IQ, 1783, I disposed 

 the 3 thermometers in the following manner: one in my garden; one on the top 

 of the high tower, as before; and the 3d on the top of St. Thomas's hill, about 

 a mile distant from the city, where, at 1 5 feet from the ground, it was nearly 

 level with that on the cathedral tower. The weather at this time proving cold, 

 favoured the experiment; and I now found the several thermometers nearly 

 aoreeing with each other in the day-time; but in the night, the cold at the lower 

 station exceeded the cold at the higher ones rather more than it did in the month 

 of September, when the weather was warmer. 



At the time of taking these thermometrical observations, I likewise noted the 

 different dispositions of the atmosphere in other respects: such as the pressure, 

 moisture, and dryness of the air; force and direction of the winds; quantity of 

 rain; whether the appearances of the sky were clear or cloudy, &c. as I appre- 



* Situated not far from ihe cathedral, at the extremity of the buildings on the north side of the 

 city. — Orig. 



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