146 LIGHT SCIENCE FOR LEISURE HOURS. 



and have shown that the following interruptions occur 

 from year to year, with very rare exceptions : 



1. 7th to 10th February. 



2. llth to 14th April. 



3. 9th to 14th May. 

 Six cold periods . . 4 , 



4. 29th June to 4th July. 



5. 6th to llth August. 



6. 6th to 12th November. 

 (I. 12th to 15th July. 



Three warm periods . j 2. 12th to 15th August. 

 I 3. 3rd to 9th December. 



It will be seen that the six most remarkable cold 

 periods, and the chief of the warm periods, are recog- 

 nisable in Scotland as well as in England. 



But on the Continent, also, these anomalies have 

 been clearly recognised. The cold weather which 

 occurs in May is prominent in the weather saws of 

 every country in Europe. Madler examined the mean 

 temperatures for May, as determined from the Berlin 

 observations for eighty-six years (VerhancUung des 

 Vereins zur Beford. des Gartenbaues, 1834), and 

 found a retrogression of temperature amounting to 

 2-2 Fahrenheit, from the llth to the 13th of May 

 which, be it noticed, is about the time when the most 

 rapid rise of temperature might be expected. Humboldt, 

 in his Cosmos, speaking of this anomalous cold, says, 

 * it is much to be desired that this phenomenon, which 

 some have felt inclined to attribute to the melting of 

 ice in the north-east of Europe, should be also investi- 



