| ree eee en ee 
os) Pee ef 
Pee EE ee ee eee Se 
C. Abbe on Terrestrial Temperature and Solar Spots. 347 
That the probable errors are on the whole very little dimin- 
ished, is owing to the presence of a few large discordances; on 
the other hand, the small probable error of the coefficient of s 
would indicate that it has a real existence. 
As the daily 2 P. M. observation may be supposed to show 
with special clearness the direct heating power of the sun, I 
have sought for a confirmation of the preceding results by 
applying the same formula to the annual means of the tem- 
peratures observed at this hour. 
The annual mean temperature at 2 P. M. is given for each 
year in the column & of the accompanying table. 
e arithmetical mean gives 
M,= +6°'830+0° 067 
p. e. of one annual mean =+0°-489 
The solution for the co-efficient of s gives 
*(t)= +7°-108(+0°-100)—s x 0° -V0801(+0° 00221) 
. &. of one annual mean =+0°465. 
This result therefore corroborates the former in indicating a 
decrease in the amount of heat received from the sun 
the prevalence of spots—a result clearly in harmony with the 
recent investigations into the nature of the solar photosphere. 
The reality of the existence of the above coefficient of s will 
be rendered more striking to the eye if the mean of several 
years’ observations is taken at the period of maximum and 
minimum spot frequency. : 
It would be interesting to seek in the above residuals for 
evidence of other temperature periods than that dependent on 
the eleyen year spot period. There are indeed plain indications 
of such a period of about fifty or fifty-five years duration— 
probably shea task with Wolf's fifty-six year period—but our 
series of observations is not extended enough to justify any 
exact conclusion. 
perature variations. Such an investigation I have begun and 
the indications are that positive results will be attained, and 
such as will demonstrate that the solar spots are but an imper- 
fect index to the periodi¢ changes in the solar radiation; these 
periodic changes besa apparently more intimately and directly 
. wit ides i 
peissenberg can be incorporated into the work. 
Cincinnati, July 20, 1870. 
