iHB SUN S SPOTS. 69 



laterally by one another, i. e., in almost equal degrees of lat- 

 itude. Our own continent, and the temperate parts of North 

 America, generally present such contrasts of temperature. 

 When our winters are severe, the season there is mild, and 

 conversely. These compensations in the local distribution of 

 heat, when associated with vicinity to the ocean, are attend- 

 ed by the most beneficial results to mankind, owing to the 

 indubitable influence exercised by the mean quantity of sum- 

 mer heat on the development of vegetation, and consequently 

 oxi the ripening of the cereals. 



While William Herschel attributed an increase of heat on 

 the Earth to the activity of the central body — a process from 

 which result spots on the Sun — Batista Baliani, almost two 

 and a half centuries earlier, in a letter to Galileo, described 

 solar spots as cooling agents. =^ This opinion coincides with 

 the experiment made by the zealous astronomer Gautierf at 

 Geneva, in comparing four periods characterized by numer- 

 ous and by few spots on the Sun's disk (from 1827 to 1843), 

 with the mean temperatures presented by thirty- three Euro- 

 pean and twenty-nine American stations of similar latitude. 

 This comparison proves, by positive and negative differences, 

 the contrasts exhibited by opposite Atlantic coasts. The final 

 results, however, scarcely give 0'7G° Fahr. as the cooling 

 force ascribed to the Sun's spots, and this might with equal 

 propriety be attributed to errors of observation and the direc- 

 tion of the winds at the localities indicated. 



It still remains for us to notice the third envelope of the 

 Sun, to which we have already referred. This is the most 

 external of the three, inclosing the photosphere, is cloudy, and 

 of imperfect transparency. The remarkable phenomena of 



* We find a reference in the historical fragments of the elder Cato to 

 an official notice of the high price of corn, and an obscuration of the 

 Sun's disk, wliich continued for many months. The " luminis caligo'^ 

 and " defectus Solis^^ of Roman authors does not invariably indicate an 

 eclipse of the Sun ; as, for instance, in the account of the long-continued 

 diminution of the Sun's light after the death of Caesar. Thus, for in- 

 stance, we read in Aulus Gellius, Noct. Att., ii., 28, '' Verba Catonis in 

 Originum quarto haec sunt: non libet scribere, quod in tabula apud 

 Pontificem maximum est, quotiens anona cai'a, quotiens Lunte an Solis 

 lumini caligo, aut quid obstiterit." " The words of Cato in the fourth 

 book of his Origines are these : I may not write what is frequently en- 

 tered in the tables of the priests, that corn was dear whenever there 

 was any decrease in the light of the Sun and Moon, or when any thing 

 obscured them." 



t Gautier. Recherclies relatives a VLiJluence que le vombre des tachet 

 Sofaires exerce sur les temperatures Terrestres,\i\ the Bibliothfque Uni- 

 teisp.Uedc Genive, Nouv. S^'rie, torn, li., 1844, p. 327-335. 



