424 



Results of Makerstoun Observations, 1844. 



TABLE XXIII. — Extreme Readings of the Barometer for each Month ; Extreme Mean Daily Heights 

 for each Month ; and Extreme Diurnal Ranges for each Month, together with the Ranges and 

 Means of the Extremes. 



Month. 



Extreme Readings. 





Extreme 



Daily Means. 



Extreme Diurnal Ranges. 



Highest. 



Lowest. 



Range. 



Mean. 



Highest. 



Lowest. 



Range. 



Mean. 



Greatest. 



Least. 





d. 



h. 



in. 



d. 



h. 



19) 



20/ 



18 



15 



11 



in. 



in. 



in. 



d. 



in. 



d. 



in. 



in. 



in. 



d. 



in. 



d. 



in. 



Jan. 



Feb. 



March 



April 



14 



3 



28 

 30 



13 





 23 

 12 



30-234 



29-869 

 30267 

 30-195 



I 5 



25 







12 



28-754 



28-559 

 28-716 

 29-298 



1-480 



1-310 

 1-551 



0-897 



29-494 



29-214 

 29-491 

 29-746 



15 



3 



29 



9 



30-168 



29-804 

 30-243 

 30-170 



6 



8 



2 



13 



28-851 



28-761 

 28-818 

 29-357 



1-317 



1-043 

 1-425 

 0-813 



29-509 



29-282 

 29-530 

 29-763 



8 



23 

 12 

 10 



0-535 



0-738 

 0-659 

 0-421 



24 



16 

 5 

 9 



0036 



0-048 

 0052 

 0055 



May 



{' 



201 

 21 f 



30-281 



6 



15 



29-569 



0-712 



29-925 



2 



30-226 



7 



29-647 



0-579 



29-936 



16 



0-371 



29 



0034 



June 



16 



13 



29-950 



13 



6 



15 



12 



9 



15 



29-263 



0-687 



29-606 



1 



29-886 



7 



29-352 



0-534 



29-619 



8 



0-327 



29 



0-045 



July 

 Aug. 

 Sept. 



20 



31 



1 



12 

 12 

 16 



29-982 

 30-089 

 30-125 



28-959 

 28-811 

 29-373 



1-023 

 1-278 

 0-752 



29-470 

 29-450 

 29-749 



27 



31 



2 



29-948 

 30-046 

 30-098 



31 



7 

 16 



29-275 

 28-992 

 29-437 



0-673 

 1-054 

 0-661 



29-611 

 29-519 

 29-767 



13 



6 



30 



0-654 

 0-653 

 0-419 



2 

 28 

 25 



0-031 

 0-060 

 0-031 



Oct. 



27 



13 



30-127 



9 

 17 



181 

 19/ 



2 



2 



28-596 



1-531 



29-361 



28 



30-070 



15 



28-619 



1-451 



29-344 



8 



0-501 



23 



0037 



Nov. 

 Bee. 



21 

 21 







8 



30 112 

 30-333 



28-697 

 29-230 



1-415 

 1-103 



29-404 

 29-781 



21 

 21 



30-079 

 30-314 



9 

 17 



28-739 

 29-261 



1-340 

 1-053 



29-409 



29-787 



14 



18 



0-463 

 0-525 



26 

 24 



0056 

 0032 



Extremes of Atmospheric Pressure for 1844. 



m. 



: 6-774. 



The highest barometer occurred Dec. 21 d 8 h = 30-333 



The lowest Feb. 25 d 18 h = 28-559 



The highest daily mean pressure occurred Dec. 21 d =30-314 



The lowest Oct. 15 d =28-619 



The highest monthly mean pressure occurred in May =29-980 



The lowest Feb. =29-321 



The greatest range of pressure in a civil day occurred February 23 d = 0-738. 



The least July 2 d and September 25 d = 0-031 



Mean = 29-446. 



\ Range = < 



JRange = l-695. Mean = 29-466. 



]Range = 0'659. Mean = 29-650. 



Pressure op Dry Air. 

 Annual Variation of the Pressure of Dry Air. — If we assume that the means at the foot of Table X. 

 accurately represent the pressures of the vapour of water in the atmosphere, the mean pressures of the dry 

 air will be obtained by subtracting them from the means for the total atmospheric pressure, Table XVIII. The 

 resulting mean pressures of dry air are as follow : — 



in. Jan. Feb. March. April. May. June. July. Aug. Sept. Oct. Nov. Dec. 



29 | -477 -141 -320 -547 '707 -273 -258 -134 .466 -121 .305 -705 

 f The least mean pressures of dry air are those for October, August, and February, and the greatest are those 

 for May and December. The means vary in the same manner as those for the total atmospheric pressure. 



Diurnal Variation of the Pressure of Dry Air. — The following Table contains the diurnal variations of 

 the pressure of dry air, obtained from a comparison of Tables XIII. and XXII. 



The variation of the pressure of the dry air thus determined is double in winter, like that of the total 

 pressure ; there is a secondary maximum and minimum in autumn, and the variation is single, with some irre- 

 gularities, in the other quarters, and for the year. The epochs of maxima and minima are as follow : — 



Max. 



Winter. Nov., Dec, Jan., + 9 h 40 m p.m. 



Spring. Feb., March, April,... 9 h 10 m p.m. 



Summer. May, June, July, 



Autumn. Aug., Sept., Oct., ... -f ll h 10 m p.m. 

 The year 1844, 12 h 10 m a.m. 



The law of variation is so different in the different quarters of the year, that no confidence should be 

 placed in these results, as exhibiting the diurnal variation of the pressure of dry air : it appears extremely 

 probable that the true pressure of aqueous vapour in the atmosphere is not to be determined by means of the 

 psychrometer. 



Min. 



Max. 



Min. 



6 h 50 m A.M. 



10 h m A.M. 



— l h 40 m p.m. 

 2 h 10 m p.m. 





4 h 10 m A.M. 



5 h 10™ p.m. 



3 h 40 m A.M. 



5 h 40™ A.M. 



-3 h 10 ra p.m. 

 2 h 40 m p.m. 



