45 



mouth, than in the neighbourhood of London : that is, we have a milder 

 winter, with a cooler summer. 



[Since the above was written I have ascertained the average mean 

 temperature at Greenwich for the past 105 years (from Mr. Glaisher's 

 remarks on the weather published in the Registrar General's Quarterly 

 Returns of Marriages, Births, and Deaths,) viz. — 



January 36"5° April 46*0° July 61 "6° October 49"6° 



February 38-6° May 52-8° Aug. 60-8° Novr. 42-3° 



March 41-1° June 58-2° Sept. 56-6° Deer. 39"i° 



It is noteworthy that the mean temperature for each month, except May, 

 was higher during the last thirty-five than in the previous seventy years 

 of this period, at Greenwich.] 



These results, as regards the winter months, may surprise those who 

 have not paid much attention to climatology, but they are quite in 

 accordance with ascertained facts. It is well known that whilst the 

 isothermal lines, (or lines of equal temperature) in summer cross the 

 British Isles from East to West, in winter their direction is from south 

 to north. In other words, in summer the mean temperature increases 

 from north to south; whilst in winter the increase is in a direction from 

 east to west; so that the former of these facts account for the lower 

 summer temperature here in the north, whilst the longitude of Cocker- 

 mouth, west of Greenwich, (about 3° 23') may in like manner account 

 for the warmer winter months. 



Very possibly, however, the means obtained for the fifteen years of 

 observation may have to be modified by a more extended series, as 

 there are known to be cycles of hot and cold years, in periods varying 

 from nine to fifteen years ; but these results agree very well with the 

 isotherms which Mr. Buchan gives on outline charts of the British Isles, 

 in his handbook of Meteorology. In the month of January, the isothermal 

 line of 39° is there represented as skirting the west coast, and passing 

 through Cumberland, to the east of Cockermouth. Whilst for July, the 

 isothermal lines of 59° and 60", cross the former to the north of 

 Cumberland, and the latter to the south of it, or about the mouth of the 

 Duddon. 



