THE EARTH IN METEORIC SHADOW. 141 



THE EARTH IN METEORIC SHADOW. 



THE occurrence of certain spells of exceptionally cold 

 weather in February, April, and May has long been 

 recognised as among the most mysterious of meteoro 

 logical phenomena. Not in every year, but still so 

 often that the change is recognised by other than 

 scientific observers, the temperature falls from about 

 the 7th to the 12th of February, from about the 10th 

 to the 14th of April, and from about the 10th to the 

 14th of May. It had been thought sufficiently strange 

 that this should have been noted, as Kaemtz long since 

 pointed out, throughout the whole of Europe ; and 

 Erman had been led, by this evidence alone, to ascribe 

 the peculiarity to some extra-terrestrial cause. When 

 it was found that the peculiarity is observable in North 

 America also, the evidence in favour of some cosmical 

 cause for the phenomena was greatly strengthened. 

 Still there were those, myself among the number, who 

 could not accept the only extra-terrestrial cause which 

 had been assigned, and were disposed to believe that 

 possibly some process usually or ordinarily taking place 

 at the observed times, as, for instance, the breaking 

 up of special ice-fields in February, April, and May, 

 might occasion the lowering of the temperature ob- 

 served at these seasons. Now, however, evidence has 

 been obtained which seems to show that the cooling in 

 question affects not the northern hemisphere alone but 



