172 METEOBOLOGICAL PERIODICITT. 



In 1868 also there was a great fall in the temperature in February, 

 and the average for the month was only equal to that of Marcn. 



In 1860, February temperature is again below January and 

 March, and there was less south wind in February than in either 

 of the other months. On the 9th, 10th, and 11th there were 

 storms of thunder, lightning, and heavy rain. 



Other remarkable depressions in the temperature of other 

 months might be given of the same kind, but these will suffice of 

 particular instances. 



No one can, I think, look at the temperature curve plotted 

 for a number of years without being struck by its strange 

 anomalies. One year the temperature runs up suddenly to its 

 maximum, and one month, or part of it, constitutes the summer ; 

 while in another year it rises to the same temperature and 

 retains it for two or three months, the temperature of each being 

 quite as high as the year of short summer. It is the same in 

 winter. The curve is pointed, or rounded, in direct accordance 

 with the circumstances which modify the sun's heating power. 

 That these are between us and the sun does not, I conceive, 

 admit of a doubt. Tear after year the sun rolls on, and the spots 

 which we see on his surface do not sem to affect his heating 

 power, or if they do, almost inappreciably ; while month after 

 month, or season after season, strange irregular changes take 

 place in the temperature, which can only be accounted for on 

 the supposition that space between the sun and earth is not 

 empty. To what extent these cosmical causes may interfere 

 may be judged from historical statements. 



Humboldt remarks with rega-rd to the occasional darkening of 

 the sun, that " a phenomenon of this kind, which cannot be ex- 

 plained by fogs or volcanic ashes, occurred in the year 1547 

 (24th to 28th August), and lasted three days. The sun was 

 reddish, and so dark that several stars were visible at noonday " 

 Similar darkenings of the sun's surface occurred in 1090 and 

 1208, but lasted for a shorter time — the former for three hours 

 and the latter for six hours.. Messier states that on the 17th 

 June, 1777, about noon, he perceived an immense number of 

 black globules pass over the sun's disc. Two other obscurations 

 of the sun, that of the beginning of February, 1106, and that of 

 12th of May, 1706, during which, about 10 o'clock in the morn- 

 ing, it became so dark tha*^ bats commenced flying, and persons 

 were obliged to light candles, do not appear to admit of any 

 other explanation. 



One other case from Roman history may be mentioned : — "At 

 certain times the sun appears to be not of his wonted brightness, 

 as it happened to be for a whole year when Csesar was murdered, 

 when it was so darkened that it could not ripen the fruits of the 

 earth."— F/r<7i7, Greor., Liber 1, &c. 



