THE SUN'S SPOTS. 373 



astronomer has himself observed, because the price of corn 

 in one part of Europe cannot be taken as a criterion of the 

 state of vegetation over the whole continent; but more espe- 

 cially because a diminution of the mean annual temperature, 

 even if it affected the whole of Europe, would afford no 

 evidence that the Earth had derived a smaller quantity of 

 solar heat throughout that year. It appears from Dove's 

 investigations of the irregular variations of temperature, 

 that extremes of meteorological conditions always lie laterally 

 by one another, i. e. in almost equal degrees of latitude. 

 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 con- 

 versely. These compensations in the local distribution of 

 heat, when associated with vicinity to the ocean, are attended 

 by the most beneficial results to mankind, owing to the indu- 

 bitable influence exercised by the mean quantity of summer- 

 heat on the development of vegetation, and consequently on 

 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. 15 This opinion coincides with 



15 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 disc, which 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 instance, we read in Aulus Gellius, Noct. Att. ii. 28, 

 " Verba Catonis in Originum quarto hasc sunt : non libet 

 scribere, quod in tabula apud Pontificem maximum est, 



G2 



