Exotic Conifers in Britain. 



321 



of the English summer. In January the mean temperature of 

 much of Ireland and of the west of Scotland and England is 

 the same as that of Avignon, Florence, and Constantinople ; 

 whereas in July London is not so warm as Memel, which lies 

 more than 5 deg. further north. In winter the greater part of 

 Britain is 10 deg. or 12 deg. warmer than Munich or Vienna, 

 whereas in July the temperature of Vienna is nearly 7 deg. F. 

 above that of London. 



While the rate of tree growth may be much affected by 

 summer temperature, what determines the question as to 

 whether a particular species may be successfully grown in a 

 place is not so much the mean summer or mean winter tempera- 

 tures as the' minimum winter temperature. On the west coast 

 of Scotland and England, and over the greater part of Ireland, 

 it is a comparatively rare event for the temperature to sink 

 below 20 deg. F., while any snow that may fall lies for, at most, 

 but a few days. In the centre and east of England and 

 Scotland two or three weeks of frost may be experienced each 

 winter, when the thermometer may sink to 15 deg. F., and 

 occasionally, though very rarely, to below zero. The figures for 

 certain stations for the five years 1 893-1 897 are shown in 

 Table I., which has been kindly compiled for the purpose of this 

 paper by the Meteorological Office. 



It is in winters of unusual severity that the climate of Britain 

 contrasts most favourably with that of the rest of Europe. 

 February, 1895, was an exceptionally cold month over the whole 

 of Europe, but the mean minimum temperature (24 deg. F.) of 

 that month in London was no lower than that experienced 

 along the west coast of France, and in the Riviera, Central 

 Italy, and Turkey. In the same month the mean minimum 

 temperature was 18*5 deg. F. in Vienna, and 16*5 deg. F. in 

 Munich, while the absolute minimum temperature recorded was 

 11 deg. F. in London, 4*5 deg. F. in Vienna, and —4 deg. F. in 

 Munich. Other data are shown in Table II., the figures being 

 given to the nearest half-degree. 



In the month of May, Britain and Austria have each about 

 200 hours of sunshine, whereas in December the amount of sun- 

 shine in Austria (50-100 hours) is about double that in Britain. 

 On the mean of the year Britain gets from 27 to 36 per cent, of 



