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.

    207/280 (page 181)
    Of 227 observations, 1389 were followed by 1 or more fair days, 100 by 2 or more, &c. as under. Ve eee Oe Ole DO LO igo 139 100 69 52 38 30 211610 6 2 1 According to the laws of chance, the probability of any number of successive fair days is found by raising 4% to the power, whose index is the pro- posed number of fair days; these probabilities being multiplied by 227 will give what the above series ought to have been, if the aurora had no influence ; it is as under. ie ed ee ts) Ly ahi a Ts, mend SR a 5 ee | From which it appears, there should not have been more than 1 aurora out of 227 followed by 6 fair days, and yet in fact there were 30; whence the inference above made is confirmed. As for the different seasons of the year, I find the aurora is more frequently followed by fair weather in summer than in winter; but the dis- tinction is not very considerable. It may be observed that the largest and most splendid appearances of the aurora as they usually happen in rainy and unsettled weather, they are frequently succeeded by one or more wet days ; but I do not find any of those very remarkable ones which happened on a fair day, was succeeded by a wet one. Upon examination of the effect of the aurora