Atmospheeic Peessuee. 
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 6th. 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. 
Spring, 
Summer, 
Autumn, 
Winter, 
Mean Meteorological. 
in. 
0-197 
176 
•268 
•243 
Meteorological for 1843. 
in. 
0-185 
•175 
•282 
•243 
Astronomical, 
in. 
0-207 
T71 
•205 
•301 
Range of Means, 
0-092 
0-107 
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. 
18 h . 
20 h . 
22 b . 
0\ 
2 h . 
4K 
6 h . 
S h . 
10". 
Mean 
Pressure. 
Range. 
in. 
in. 
in. 
in. 
in. 
in. 
in. 
in. 
in. 
in. 
January 
29-333 
29-353 
29-363 
29-365 
29-353 
29-357 
29-358 
29-367 
29-374 
29-357 
0-041 
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 1 
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 J 
The observations in the first week of January were not made use of in obtaining the hourly means for 
