XCll 



General Results of the Makerstoun Observations 



The mean pressure for the six months October to March is 0-100 inch less than that for the six months 

 April to September, while the range of the quarterly groups for the meteorological seasons is only 0-057 in. 

 Neglecting therefore the minor variations, the law of atmospheric pressure is distinguished by a maximum for 

 the six months during which the sun is north of the equator, and a minimum for the six months during which 

 it is south of the equator. The means for the separate quarters show no direct connection with temperature 

 since April to June, and July to September have nearly the same mean pressure. 



Table 84. — Mean Differences of the Daily Mean Atmospheric Pressure from the Monthly 

 Mean, for each Month in the Years 1843-6. 



Year. 



Jan. 



Feb. 



March. 



April. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



1 



Mean. 





in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



1843 



0-412 



0-281 



0-261 



0^217 



0218 



0^270 



0-184 



0^237 



0^1 67 



0^262 



0-274 



0-126 



0^242 



1844 



•279 



•274 



•310 



• 192 



•142 



.127 



•126 



•216 



•151 



•304 



•323 



•224 



•222 



1845 



•257 



•145 



•208 



•323 



•189 



•258 



•197 



•214 



•329 



•250 



•302 



•313 



•249 



1846 



•373 



•255 



325 



•301 



•256 



•273 



•195 



•176 



•306 



•337 



•394 



•327 



•293 



Mean 



•330 



•239 



•276 



•258 



•201 



■232 



•175 



•211 



•238 



-288 



•324 



•247 



•252 



1 



192. Annual Variation of the Differences of the Daily 3Iean from the Monthly Mean Pressure. From 



the means for four years in Table 84, the daily mean pressure of the atmosphere varied most in the months of 

 November and January, and it varied least in July. The following groups give the greatest and least quarterly 



means,- 



Nov. Dec. Jan. 



Feb. Mar. April, 



May, June, July, 



Aug. Sept. Oct 



in. 



in. 



in. 



in. 



0-300 



0-258 



0-203 



0-246 



The daily mean height of the barometer differs on the average three tenths of an inch from the monthly 

 mean in the winter quarter, Nov.-Jan., and only two tenths of an inch in the summer quarter. 



Table 85. — Monthly Means of the Diurnal Ranges of the Atmospheric Pressure for the 



Years 1843-6. 



Year. 



Jan. 



Feb. 



March. 



April. 



ilay. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Mean. 





in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 



1843 



0^342 



0-180 



0-206 



0-235 



0151 



0169 



0^194 



0^166 



0-165 



0-285 



0-355 



0^207 



0221 



1844 



•224 



•282 



-298 



-185 



•124 



•148 



•156 



• 181 



•134 



•234 



•196 



•145 



•192 



1845 



•320 



-243 



-236 



•222 



•131 



•184 



•181 



•164 



-223 



-208 



•269 



•452 



•236 



1846 



-283 



• 202 



-269 



-160 



•183 



•142 



•172 



•149 



■165 



-294 



•223 



•217 



•205 



Mean 



-292 



•227 



-252 



•200 



•147 



•161 



•176 



■165 



-172 



-255 



•261 



•255 



•214 



193. Annual Variation of the Diurnal Range of the Atmospheric Pressure. — From the means of the diurnal 

 ranges for each month in the four years 1843-6, the diurnal range is least in May, and it is greatest in 

 January ; the following groups give the greatest and least quarterly means, — 



Nov. Dec. Jan. 



Feb. Mar. April, 



May, June, July, 



Aug. Sept. Oct 



in. 



in. 



in. 



in. 



0-269 



0-226 



0-161 



197 



