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.

    58/280 (page 32)
    MEAN STATE OF THE HYGROMETER, AT KENDAL. 1788)1789..1790.1791.1792. ican of tBe January 40.3) 83.4; 85 | 85 |102.6 79.3 February | 54.7} 81 | 92.8] 97 {100.5 85.2 March 81 |106 |109 |105.7/112 102.7 April So I 2a Loe 25 113.9 May 116 |123 {129 |123 /128 123.8 June To / Tikace oe aoe oA 131 July 104 {126 |126 |181 {134 124.2 August {113 {1382 |121 /129.6/138.5 126.8 September|108.5)114 {117 |129 |120.7 EV 7.2 October /102. {104 {109 |119 |123.3 NO ees November] 87.6} 99 |104 |113 {106.4 102 December {100 | 85 | 92 |107.7/102.6 97.5 Ann.means| 93.3)107.7)112.1|115.9 Driest.. = -. 1138 i140 4141-1144 4T50 ae Moistest..| 15 63 71 65 83 It is obvious, from the means of the several years, and like- wise from the extremes, that the cord has been increasing in length each year, so that, in similar states of the air, the index pointed at greater numbers each year successively ; this increase too appears to have been nearly in arithmetical progression after the first year.—In consequence of this increase in the length of the cord, some allowance ought to be made in comparing the mean state of the hygrometer in the different months of the year; thus, if the months of June or July be taken for a standard of comparison, then the means of the preceding months must be increased, and those of the following diminished, in such propor- tion as the annual increase shall require. The above mentioned instrument serves to show a variation in the dryness or moisture of the air; but it is very inadequate to the purpose for which an hygrometer is desired.