270 ABSTRACTS OF THE MAKERSTOUN OBSERVATIONS, 1843. 
TABLE IX.—Daily, Weekly, and Monthly Means of the Pressure of Aqueous Vapour in inches of 
Mercury, as deduced from Tables I. and VII. 
March. 
. in. 
tates 0-162 ‘ 
| 0154] -183 | -167 |[ -275]| -256| -355|[ -371]| -410| -529 ; 
| +170 -166 -166 272 281 278 404 -414 | [ -423] 337 +232 | [ -257] 
| +157 : 
: 337 . 
22 [ -250]| -228 +304 +315 +304 +319 +397 -390 +356 |[ -245]| -239 -308 
23 +243 +223 +303 | [ -265]| -324 +360 | [ -375]| +324 +380 +289 +222 -323 
24 +281 +223 -261 +238 -306 +348 -308 -335 | [ -312]| -238 186 | [ -299] 
25 -273 -196 +223 +239 331 |[ -317]| +379 +383 +282 -208 -186 331 
26 -263 | [ -194]] [ -220]} -207 +359 +322 | -489 +389 +229 +179 | [ -237]} -294 
27 -342 -181 -182 -235 -328 -296 +357 | [ -363]| -231 +185 +311 +279 
28 || -224 +182 +174 +264 |[ -307]| -256 +385 -423 +233 264 +295 -281 
29 || [ -259]| -176 -261 +241 -298 +399 +331 -262 | [ -202]| -220 277 
30 || -217 -224 |[ -260]|} -277 -334 | [ -386]} -320 -418 -198 +283 +258 
31 +286 :299 +308 | +365 -390 -196 [ -220] 
1 | i] ia ae ee | = 
Mean || 0-220 | 0-184 | 0-223 | 0-253 | 0-281 | 0-320 | 0-387 | 0-409 | 0-382 | 0.245 | 0-238 | 0-280 
| | 
The quantities in Table IX. have been deduced from Tables I. and VII. by means of Dr Apsoun’s for- 
mula, taken approximately, namely (Proceedings of the Royal Irish Academy, 1840), 
a = x — the temperature of evaporation being above 32° 
RR: Wo 
=P — 96 * 30-0" 
Where ” is the tension of aqueous vapour in the air, given in the previous Table; /’, the tension of aqueous 
vapour, the air being saturated at the temperature of evaporation; d, the difference between the temperatures 
of the air and of evaporation; 29-7, the mean barometric pressure. The values of f’ were obtained from 
the Table, page xl., Introduction to the Greenwich Observations, 1842. The errors for the monthly or hourly 
means, from the use of the approximate formula, are small, the greatest error is probably under 0:003 in. The 
errors of the daily means will be due chiefly to the want of the three two-hourly observations. 
The Annual Variation of the Pressure of Aqueous Vapour follows the same march as the temperature of 
the air. The greatest monthly mean is that for August, and the least that for February; the former being 
0°409 in., the latter beg 0-184 in., and the annual range of the monthly means 0-225 in. The means for 
the mean meteorological seasons, and the meteorological seasons for the year 1843, are— 
a acc cpiisinbec oo Mawes cenadveniss suns bster below 32° 
Spring, Mar., Apr., May, 0-252 Apr., May, June, 0°285 
. Summer, June, July, Aug., 0°372 July, Aug., Sept., 0°393 
Autumn, Sept., Oct., Nov., 0°288 Oct., Nov., Dec., 0°254 
Winter, Dec., Jan., Feb., 0°228 Jan., Feb., Mar., 0:209 
The year 1848, 0:283 inch. 
