436 



Prof. C. V. Zenger on the Periodic Change 



Year. 



Months. 



»c 



Inclination. 



Period. 



Average 

 of annual 

 tempera- 

 ture. 



Difference. 



1843. 



1848. 

 1852. 

 1857. 

 1862. 

 1866. 



725 



300 

 1100 

 6-70 

 2-60 

 9-80 



270° 

 180 

 90 

 

 270 

 180 



Mean. 

 Minimum. 



Mean. 

 Maximum. 



Mean. 

 Minimum. 



From mean to min. 

 ,, min. to mean. 

 ,, mean to max. 

 „ max. to mean. 

 .,, mean to min. 



6949 

 7-881 

 6-922 

 7-178 

 8-402 



+0-959 R. 

 + 1-224 „ 



It results that during the period of a whole revolution of the 

 nodes from 1848-66 the average of annual temperatures is larger 

 for 1848-52 (from minimum to mean inclination) than in the 

 following period, 1852-57 (from mean to maximum); the same 

 follows from the periods 1862-66 (from mean to minimum) and 

 the preceding 1857-62 (maximum to mean). 







Average. 



Difference. 



Taking the period 1843-48. 



1848-52. 



1852-57. 

 1857-62 



Mean to min. 

 Min. to mean. 



Mean 



Mean to max. 

 Max. to mean. 



Mean 



6-949 



7-881 



+0-932 

 +0-256 



7415 



6922 

 7-178 



7-050 



we find a difference between the averages of annual temperature 

 during the periods of minimum and of maximum inclination of 

 o, 365, the difference of the averages of temperatures for 

 1848-57 and 1857-66 being 0°-339. The latter period of 9| 

 years (calculated in both ways) is found to be warmer; and the 

 secular increase of temperature will therefore be from 1 0, 883 to 

 2°-028. 



Period. 



The mean temperature calculated for 1840-53 is 7-428 13 years. 



1854-66 „ 8-035 13 „ 



Difference 607 



The secular increase would be 2°*33, a number rather too great ; 

 for Mr. Glaisher found a secular increase of l°'l C. by means 

 of 30- year periods for London. 



On the contrary, the averages of atmospheric pressure during 

 the periods of maximum inclination are greater than those of 

 the periods of minimum inclination : — 



