Meteorological observations and essays / By John Dalton.

  • John Dalton
Date:
1834
Catalogue details

Licence: Public Domain Mark

Credit: Meteorological observations and essays / By John Dalton. Source: Wellcome Collection.

    55/280 (page 29)
    The annual mean at Keswick may perhaps be stated more accurately at 46°, as the evening observations were taken too soon to give the true mean temperature. It may, however, be proper to observe here, that the time or times of the day at which the observations ought to be made, in order to determine the true mean, has not, that I know of, been ascertained. I made the following observations on the temperature of a pump well, the surface of which is usually from 3 to 6 feet below that of the ground; at the end of January its heat was 45°; February, 45°; March, 46°; April, 46°.5; May, 48°; June, 50°; July, 51°; August, 52°; September, 50°; October, 48°.5 ; November, 47°.5; December, 45°.—These observations give an annual mean of 47°.8. About the middle of June, 1793, I found the temperature of several wells in Kendal, after having pumped a few gallons of water from each; six of the deepest, being from 5 to 10 yards below the surface of the ground, were just 48° each; three other deep ones were 47°.5; one not quite so deep was 46°; and three that were only 2 or 3 yards below the surface of the ground were 49° each. The deep ones, I believe, in general are subject to very little variation in temperature all the year round. From these observations on the temperature of wells, I am inclined to think, the heat of the earth at 10 or more yards depth is not the same, at Kendal, as the mean heat of the air, but something greater, Perhaps this is a general fact; the tem- perature of the cave of the observatory at Paris, which is 30 yards below the pavement, is 53°.5; whereas the mean heat of the air there, is only 52°.—However this may be, I cannot believe the mean heat of the air at this place is so great as that of the pump water.