200 



DISCUSSION 01' THE ANNUAL FLUCTUATION 



He further communicated two tables,^ showing by five-year means that January was 

 warmer than February in ] 841-5, and has since become gradually colder, and that 

 by forming two groups of years, whose centres were distant about 20 years, the 

 temperature of winter and spring (1841-50) had now (1861-8) become lower, and 

 the temperature of summer and autumn higher, and suggests an examination of the 

 larger series of places in the United States with a view of learning whether the 

 progressive change is general or confined to special locaHties. 



In taking up the study of this subject the existence of such an inequality was 

 confirmed for a number of places, and its geographical range and epochs were 

 approximately determined. Selecting, from our general tables of monthly tempera- 

 tures, such stations as appeared to me best suited for the purpose, on account of 

 their location and length of record, the differences (J. — F.) of the monthly means of 

 January and February, as well as the differences (J. — A.) of the monthly means of 

 July and August, were formed for each year, and the results were united into 

 means of five years: — 



Table of a 



iJ^ 



erences {J 



-F.): 



a -\- sign indicates February 



colder than Ja 



nuary, 



a — sic, 



n th 



e reuerse. 



Epochs. 









rt 



S 



s 



tK 



u 









in 







i 







 c 





IS 







i 



s 





p 

 H 



■a 

 P-i 



U 



c 

 > 



s 



r 











;, 



(, 







^ 



^ 



^ 



^ 



^ 



^ 



^ 



^ 



^ 



1781-85 













—1.9 

















1786-90 











+2.1 

































1791-95 











— 



.8 



—0.8 



— 



5 























1796-1S00 



— V.8 









— ; 



■5 



—1.6 



— I 



4 























iSoi-05 



—4.1 









— : 





—2.4 



—2 























■ 1 



1S06-10 



— 2.3 



-4.6 





— ; 



•4 



—4.2 



—4 



5 





—4 



5 















• B 



iSu-15 



-4.6 



—4.0 





— : 



•9 



— 5.4 



— 2 



5 





— 2 



.0 















1 



I Si 6-20 





— 2.9 





— 1 



•9 





— I 



2 





—3 



.6 















• I 



1 82 1-25 







— 4.2 





— : 



•7 





— 2 



4 







7 







— 2.9 



■ — 3 



3 





• 1 



1S26-30 







-J-5 





— : 



.1 





2 



S 





— 2 



I 







—4.0 



—3 



6 





■ 1 



1S31-35 







— 1.2 



— 3-2 













3 



+ i".6 



— I 



7 



—3-1 



-4.6 



— 3-0 



^i 



I 



+o.3| 



1S36-40 







—2.8 



—3-3 









■ — I 



3 



+ 1-4 



— 



I 





—2.9 



— I.I 



—3 



3 





1841-45 







— 0.1 



+0.1 







—0.7 



+0 



3 



+2.6 



[+2 



I] 



[+i'-7] 



[+0.3] 



[+0-5] 



[-1 



7] 



°-2 1 



1846-50 







[+0.1] 



[+1-2] 







+ [2.3] 



[+1 



6] 



[+2.6J 



+ 1 



5 



+0.5 



-|-0.2 



— 0.1 



—4 







— 3-3i 



1851-55 







—4.9 











— I 



I 



-1-0.8 



— 2 







—4.2 



-6.5 



-3-S 



—6 







— 6.6l 



1S56-60 







-5.S 











— 3 



4 



—0.4 



— 2 



6 



—5-1 





—4.4 



—3 



9 



5.3 1 



1861-65 

















2 



9 



—1.6 



. — 2 



6 



—3-7 







—4 



2 



5.6 1 



1866-69 

















— 2.1 



— 3 



9 











__l 



' Comparison of means of Jan. and Feb. in groups of five years, from observations at Toronto: — 

 1841-45 Jan. warmer than Feb. 2°. 6 j 185G-60 Jan. colder than Feb. 0°.3 

 1846-50 " " " " 2.6 1861-65 " " " " 1.5 



1851-55 " " " " 0.9 I 1866-69 " " " " " 2.1 



Comparison of seasons in two groups of years : — 



Winter. Spring. Summmer. Autumn. 



1841-50 25°.l 41°. 64°.7 46°. 4 



1861-68 23.4 40.3 65.6 4T.4 



Difference _1,T — O.T -|-0.9 -fl.O 



In General Sabine's paper, the coldest day is Feb. 14, the warmest July 28. 

 In 1849-68 " " " " Jan. 6, " " " 22. 



(Letter to the Secretary of the Smithsonian Institution of Jan. 25, 18*70.) 



