66 



between 40 and 50 degrees north in the months of March, 

 April, and even May." And such an occurrence was sug- 

 gested by Mr. Fairbairn, in a communication to the British 

 Association in 1842, " as a probable cause of the low tempe- 

 rature of the summers of 1838, 1839, 1840, and 1841."* 

 But it would not be easy to determine beforehand what 

 seasons, or at what particular time, these icebergs, which are 

 detached from the general mass of ice in the Polar Seas by 

 local and accidental causes, shall occur to produce the unfa- 

 vourable effect which they have on our climate. 



Take again the phenomenon of that "peculiar haze or 

 smoky fog," as it has been called, occasioned by the presence 

 of foreign matter in the atmosphere, traceable in some cases 

 to volcanic eruptions in regions far away, and causing more 

 or less obscuration of the sun for long periods of time. A 

 notable instance of this fog occurred in the year 1 783, sup- 

 posed by some to have been due to a volcanic eruption in 

 Iceland, which broke out on the 8th of May, and continued 

 till August. This mist is said to have overspread " a consi- 

 derable portion of Europe and Asia, as well as of the north 

 of A.frica,"-f- the darkness and thick air which it occasioned 

 continuing for nearly two months. It forms the subject of 

 one of White's Letters in his " Natural History of Selborne,"| 

 and is also alluded to by Cowper in one of his letters to the 

 Eev. John Newton, dated June 13, 1783. The latter says, — 

 " The fogs I mentioned in my last still continue, though, till 

 yesterday, the earth was as dry as intense heat could make it. 

 The sun continues to rise and set without his rays, and hardly 

 shines at noon, even in a cloudless day. At eleven last night 



* See also " The Athenaeum," No. 1,726, p. 710, where the late Admiral 

 Fitzroy, in an article on "The Weather," suggested that icebergs may have 

 been the cause of the wet cold summer of 1860. 



tSee "Humboldt's Cosmos," vol. iv., part 1, p. 405, where he expresses a 

 doubt as to its having been caused by volcanic eruptions. 



X Letter Ixv. to Daines Barrington, 



