Atmospheeic Pkessure. 



279 



The diurnal ranges have been obtained, in the first week in January, by taking the differences of the highest 

 and lowest readings included between the first observation on the civil day and the first observation of the next 

 civil day ; the range for the 7th (Saturday) was obtained by including the last observation on the 6tli. For 

 the remainder of the year, the range for Mondays was obtained by including the first observations of Tuesday, 

 and the range for the other days of the week by including the last observations of the previous days. 



Mean of the Diurnal Ranges of the Atmospheric Pressure. — The diurnal ranges are least in May, the mean 

 for that month being 0^151 in., and greatest in November, the mean being 0-355 in. The following are means 

 for the three classes of groups, namely, 



The mean meteorological seasons, for which June, July, and August constitute summer. 



The meteorological seasons for the year 1843, for which July, August, and September constitute summer. 



The astronomical seasons, for which May, June, and July constitute summer. 



Seasons. 



Mean Meteorological. 



Meteorological \ 



Spring, 

 Summer, 

 Autumn, 

 Winter, 



in. 



0-197 

 •176 

 •268 

 •243 



0^185 

 •175 

 •282 

 •243 



Range of Means, 



0092 



0-107 



Astronomical. 



0-267 

 •171 



•205 

 •301 



0-130 



The diurnal ranges are least for Summer of all the groups, and greatest for Autumn in the two meteoro- 

 logical groups, but greatest for Winter of the astronomical group. The latter group seems the most distinct, 

 the difference of the means is also greatest for it. 



The mean of all the diurnal ranges for the year 1843 = 0^221 inch. 



TABLE XVIII. — Hourly Means of the Height of the Barometer for each Month and Quarter 



of 1843. 



Period. 



18h. 



20"^. -2 



"2^. 



0\ 



2h. 



41'. 



Sh. 



8'>. 



\0^. 



Mean j. 

 Pressure. 



ange. 





in. 



in. 



in. 



in. 



ill. 



in. 



Hi. 



in. 



m. 



in. 



in. 



January 



29-333 



29^353 29 



363 



29^365 



29^353 



29357 29 



358 



29^367 



29374 



29-357 



041 



February 



•474 



•482 



501 



•511 



•498 



•493 



501 



•515 



•520 



•499 



046 



March 



•647 



•662 



669 



•670 



•662 



•656 



658 



•670 



•672 



•662 



025 



April 



•480 



•484 



486 



•484 



•477 



•472 



477 



•494 



•507 



•487 



035 



May 



•633 



•636 



634 



•628 



•619 



•606 



598 



•607 



•610 



■620 



038 



June 



•614 



■621 



624 



•627 



•624 



•616 



608 



•613 



•622 



■619 



019 



July 



•641 



•641 



641 



•642 



•633 



•629 



622 



•627 



•632 



•635 



020 



August 



•662 



•669 



668 



•660 



•652 



•641 



635 



•645 



•657 



•656 



034 



September 



•926 



•941 



949 



•944 



•933 



•926 



926 



•935 



•941 



•935 



023 



October 



•402 



•414 



419 



•415 



•407 



•394 



389 



•391 



•391 



•401 



030 



November 



•431 



•441 



460 



•470 



•476 



•481 



493 



•499 



•503 



•471 



072 



December 



•962 



•962 



975 



•977 



•959 



•953 



956 



•957 



•961 



•962 



024 



Spring 



•587 



•594 



596 



•594 



•586 



•578 



578 



■590 



•596 



•590 



018 



Summer 



•639 



•644 



644 



•643 



•636 



•629 



622 



•628 



•637 



•637 



022 



Autumn 



•586 



•599 



609 



•610 



•605 



•600 



603 



•608 



•612 



•602 



026 



Winter 



•590 



•599 



613 



•618 



•603 



•601 



605 



•613 



•618 



•606 



028 



The Year 



•600 



•609 



616 



■616 



•608 



, -602 



602 



•610 



•616 



■609 



016 



The observations in the first week of January were not made use of in obtaining the hourly means for 



