310 



DISCUSSION OF THE SECULAR VARIATION 





Fort Leavenworth, Kan. 



Fort Gibson 



Indian Ter. 



Fort Jes 



up. Fa. 



San Franc 



isco, Cal. 



>< 



C. II. 4th or. 



C. III. 



4th or. 



C. I. 



4tli or. 



C. V. 



4th or. 





Q 



Q 



P 



^ 



Q 



^ 



^ 



^ 



IS20 



















IS2I 



















IS22 



















1823 











67'3 









1824 











69.2 



68.4 







1825 











67.7 



68.5 







IS26 











68.9 



68,6 







1827 











69.1 



6S.4 







1828 







63.0 





68.1 



67.6 







1829 







60.9 



62.3 



65.1 



66.2 







1830 



56.6 





64.6 



61.6 



66.4 



65,1 







I83I 



49.8 



52.4 



57-7 



60.7 



62.6 



64.8 







1832 



53-4 



53-1 



61.3 



60.5 



66.0 



65.5 







IS33 



55-5 



53-6 



61. 1 



60.7 



67.1 



66.4 







1834 



52.4 



52.8 



61.S 



60.3 



67.S 



66 I 







1835 



51-7 



51-5 



58.1 



S9.6 



64.0 



65.0 







1836 



48.7 



51-0 



59.0 



59-5 



63-7 



64.4 







IS37 



52.9 



51-4 



60.8 



59-7 



65.1 



64.6 







IS38 



5 1. 1 



52.0 



58. 1 



60.0 



64.3 



65.4 







IS39 



53-6 



52.2 



61.9 



60.3 



67.3 



66.4 



... 





IS40 



Si-4 



52.0 



60.5 



60.4 



67.8 



66.6 



... 





1841 



51.2 



51.6 



59-1 



60.3 



65-1 



66.1 







1842 



52.8 



51-4 



61.6 



60.3 



66.4 



65.7 







IS43 



49.0 



51-4 



59-3 



60.5 



64.3 



65.5 







1844 



52.7 



52-3 



61.5 



60.8 



66.3 



65.7 







1845 



54.8 



53.6 



61.4 



61. 1 



65-7 









1846 



55-3 



53.3 



61.5 



60.7 











1847 



49.8 



52.1 



59-1 



60.0 











1848 



51-7 



51-7 



59-6 



59-5 











1849 



52.2 



51.9 



S9-S 



59'9 











1850 



52.0 



52.2 



60.4 



60.2 











1851 



53-2 



52.3 



61.4 



60.3 







5S.5 





1852 



51-5 



53.0 



59.0 



60 I 









57-8 



IS53 



53-1 



53-9 



60. 1 



60.3 







57-2 



57-7 



1854 



55-9 



54-1 



61.8 



60.6 







56.3 



57-3 



1855 



54-3 



53-4 



60.4 



60.1 







57-8 



56.S 



1856 



50.0 



52.4 



58-4 



59.0 







56-3 



56.6 



1857 



52.2 



52.6 



58.7 









56.S 



56.2 



IS58 



55-3 



53.6 











,55-7 



.S5-7 



IS59 



52-9 



54-3 











54-9 



55-4 



IS60 



56.0 



54-4 











55-4 



55-2 



IS6I 



54.0 



S4.0 







'... 





SS-5 



55-2 



1862 



52.7 



S3- 1 











54-7 



55-2 



1863 



52-9 



52.7 











55-2 



55-3 



1864 



52.0 



52.6 











56.3 



55-4 



1865 



53-5 



52.5 











54.8 



55-5 



1 866 



52.0 



52-3 











55-4 



55.6 



1867 



51.8 



52.0 











56.3 



55-9 



1868 



52.1 



52.0 











55-3 



56.3 



1869 



51-3 



52.2 











58.0 



57-2 



1870 



54-1 













57.6 





The character of the secular variation in the mean annual temperature, as 

 exhibited on the accompanying plate, is that of a series of irregular waves repre- 

 senting a succession of warmer and colder periods, during which, however, the 

 mean temperature d.eviates only about one or two degrees, in excess or defect, from 

 its normal value. Irrespective of the minor irregularities, which have to some 

 extent been eliminated, some of the single progressions appear quite systematic; 

 tlius, for instance, at New Haven, the temperature steadily declined from 1802 to 

 1817, it then increased till 1827, after which it again decreased, reaching a decided 

 minimum in 1836. These undulations, when compared for a number of stations 

 exposed to similar climatological conditions, approach to parallelism over large 

 tracts of country, and exhibit considerable uniformity in their general character ; 



