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.

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    made, or rather recorded, betwixt the years 500 and 1716. Since 1716, there has scarcely been a year without a number of these appearances. He records one hundred and sixty-three, which hap- pened between 1716 and 1732. In 1728, there were thirty ; in 1724, only two. Dr. Tuomson, in the 4th Vol. of the Annals of Philosophy, page 427, has given an article on the aurora borealis. In this, we find a table of the heights of several aurore, as estimated by the observers of the last century, most of which are taken from a work of Berean, rarely to be met with I believe in this country. Their heights are very discordant, no doubt owing chiefly to the want of correct data for the calculation. They seem mostly to have esti- mated the heights as being some aliquot part of the earth’s radius, as + 44,4, or 7 of the same; that is, from one thousand miles to three hundred, and under. Notwithstanding this, the brilliant aurorz that occur in these times, have just the same ap- pearances as those which were observed a century ago ; and the description which Dr. Hatuzy gave of the one in 1716, would equally apply to any grand display we have had since, either in this country, or any part of Europe. There is not then any reason, from the optical appearances, to con- clude that the aurore are materially variable in their heights at different times and places. Though the Astronomers and Mathematicians of the last century failed in ascertaining the exact height of the aurora, they had abundant proof it