Tempeeatuee of the Aie. 405 



When these differences which are due to the temperatures on Sundays are applied as corrections to the 

 means at the foot of Table I., we obtain the foUo\ving as the mean temperatures for each month of 1844 : — 



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



37°-35 32°-48 38°-36 46°-77 48°-49 54°-14 55°-55 54''-08 52°'30 45°-74 42°-85 32°-04 



The temperature of the air in 1844 was a maximum in July and a minimum in December and February. 

 The variation of temperature for 1844 has the mean form ; the three months having the highest mean tempera- 

 ture are June, July, and August, and the thi'ee having the lowest mean temperature are December, January, 

 and February ; the means for the meteorological quarters are — 



Winter, Dec, Jan., Feb., ... 33''-99 Summer, June, July, Aug., 54°-59 



Spring, March, April, May, 44°-52 Autumn, Sept., Oct., Nov., 45°-04 



The mean temperature for the year 1844 = 45°-04 



Differences of the Daily Mean Temperatures from the Monthly Means. — The following are the average dif- 

 ferences for each month of 1844 : — 



The difference is least in the months during which the sun is north of the equator : the mean for the 

 six winter months, October-March, being 4°-09, and for the six summer months, April-September, being 2°-55. 

 The oscillations of the daily mean temperature do not appear to be at all related to the variations of the diur- 

 nal range. 



Approximations to the Daily Mean Temperature. — The following are the mean errors, for each month of 

 1844, of the mean tempei-ature for a civil day, as obtained from the observations of the self-registering thermo- 

 meters by the formulae 



m, -I- M , 2 + ^^ 

 t = — ' — 2 1" ^ 1°" * = o + " 



where t is the approximate mean temperature for the civil day for which m^ is the minimum temperature of the 

 morning, mo is the minimum temperature on the morning following ; M is the maximum temperature, and c 

 is the correction of the monthly mean, obtained by the previous portions of the formulae, to the true mean, 

 (see Table IV.) 



The average of the en-ors by the first formula is 1°-17, and by the second it is 0°-93 ; the second formula 

 is therefore superior to the first ; the probable error by the second formula does not exceed one degree in any 

 month. The values of the corrections c may be determined from two or three years' observation. It is pro- 

 bable that better approximations to the mean temperature of the astronomical day would be obtained by means 

 of the form ula 



M, -H Mj 



2 "^ "* 



*= 2 + " 



where Mi and Mo are the maxima near the commencement and near the termination of the day, m being the 

 intermediate minimum. 



MAG. AND MET. OBS. I 844. 5 jj 



