304 



Abstracts of the Makeestoun Observations, 1843. 



TABLE XXXVI. — Means of the Estimated Surface of Cloud at the Hours of Observation, for each 



Month and Quarter in 1843. 



Period. 



IS''. 



20i. 



22ii. 



Oh. 



Sh. 



4i>. 



ei. 



8i>. 



10^. 



Mean. 

 6-41 



Range. 



January 



5-53 



7-35 



7-69 



8-02 



6-98 



7-75 



7-28 



5-20 



515 



2-87 



February 



6-97 



7-80 



7-05 



7-76 



7-95 



8-17 



7-78 



6-40 



7-42 



7-41 



1-77 



March 



6-56 



7-37 



7-33 



7-03 



7-28 



7-27 



7-33 



6-82 



6-06 



6-83 



1-31 



April 



7-08 



7-45 



8-61 



8-84 



910 



8-90 



9-02 



7-41 



6-40 



7-75 



2-70 



May 



7-86 



8-40 



8-01 



8-14 



806 



7-83 



7-14 



7-51 



7-60 



7-81 



1-26 



June 



8-59 



8-50 



8-26 



7-62 



7-40 



7-38 



7-40 



6-36 



701 



7-66 



2-23 



July 



7-68 



8-29 



901 



9-48 



8-21 



7-53 



7-96 



7-28 



6-82 



7-83 



2-66 



August 



6-44 



6-20 



5-37 



6-66 



6-95 



6-74 



6-87 



6-53 



5-67 



6-30 



1-58 



September 



6-12 



6-22 



4-57 



4-95 



5-10 



4-88 



511 



4-88 



4-58 



5-20 



1-65 



October 



5-83 



6-35 



6-36 



6-71 



7-36 



6-83 



6-42 



5-56 



5-65 



6-19 



1-80 



November 



5-90 



7-16 



6-53 



6-63 



6-72 



5-92 



5-79 



5-84 



5-46 



6-08 



1-70 



December 



6-47 



6-87 



8-00 



8-20 



7-62 



7-29 



601 



6-77 



6-73 



6-98 



2-19 



Spring 



7-17 



7-74 



7-98 



800 



8-15 



8-00 



7-83 



7-25 



6-69 



7-46 



1-46 



Summer 



7-57 



7-66 



7-55 



7-92 



7-52 



7-22 



7-41 



6-72 



6-50 



7-26 



1-42 



Autumn 



5-95 



6-58 



5-82 



6-10 



6-39 



5-88 



5-77 



5-43 



5-23 



5-82 



1-35 



Winter 



6-32 



7-34 



7-58 



7-99 



7-52 



7-74 



7-02 



6-12 



6-43 



6-93 



1-87 



The Year 



6-75 



7-33 



7-23 



7-50 



7-39 



7-21 



7-01 



6-38 



6-21 



6-87 



1-29 



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

 month ; no observations having been made at 1 8^ in the second week, a correction was applied to the mean for 

 that hour of —0*48, obtained from Table XXXIV. as follows : — 



{Mean cloud, Jan. 9-31, = 663, minus mean cloud, Jan. 16-31, = 7'11} = — 0-48. 



The means were afterwards corrected by +0"30, in order to render the mean for that month from these 

 means equal to that obtained, Table XXXIV., from all the daily means. 



Diurnal Variation of the Surface of Cloud. — The means for the various months present considerable ir- 

 regularities, the maximum surface of cloud, however, occurs, with two or three exceptions, between 1 1 a.m. and 

 3 P.M. The following are the interpolated periods of the maximum surface of cloud for each of the mean me- 

 teorological seasons (as in the previous Table) : — 



Spring, the max., l'^ 0™ p.m. 



Summer, lO^^ O"' a.m. 



Autumn, 7*^ 0"^ a.m. ; a Secondary min. about 9^ 30™ a.m. ; a Secondary max. I'' p.m. 



Winter, 11^ 0°^ a.m. ; 1^ Qi" p.m. ; S^^ p.m. 



There are other secondary maxima and minima, but they are probably accidental. 

 The periods for the astronomical group of seasons are as follow : — 



Spring, the max., 3^ p.m. 



Summer, 9^ a.m. 



Autumn, 2^ p.m. ; a Secondary min. 9^ a.m. ; a Secondary max, 6^ aju. 



Winter, 11*^ a.m. 



The secondary minimum and maximum are well marked for autumn of this group ; there are also inflexions 

 or minima in the summer and autumn about 3^ p.m., the time at which inflexions occur in the curves for the 

 aqueous vapour (Table XI.) From the astronomical group, the maximum surface of cloud seems to occur 

 after noon in the spring and autumn, and before noon in the summer and winter. The minimum occurs after 

 9^ p.m. 



The maximum in the means for the year occurs shortly before noon ; a secondary maximum is shewn about 

 7*^ a.m. ; and a secondary minimiim about 9^ a.m. 



The Diurnal Range of the Surface of Cloud, as far as it can be deduced from the 9 two-hourly means, 

 is a minimum in autumn and a maximum in winter. 



