6i8 SCIENCE PROGRESS 



even where suitable conditions of temperature exist. Destruc- 

 tive as snow may be in certain circumstances it cannot preclude 

 the growth of forest, and is not, as is commonly supposed, 

 responsible for the creeping of certain varieties of trees. 

 Precipitation and humidity of the air may be equally important 

 to tree growth. But it will suffice to say that the rainfall of 

 the United Kingdom from May to August averages nearly 

 9 inches, while investigations have shown tree growth to be 

 possible where 2 to 4 inches of rain falls in the vegetative period, 

 provided, at the same time, that the humidity of the atmosphere 

 is not less than 50 per cent. 



Wind if strong and steady may render the growth of trees 

 impossible, but light is nowhere known to be insufficient. 



Contemplating these absolute climatic limitations it is ap- 

 parent how little they come into effect in the United Kingdom, 

 for only 3,537,172 acres lie above 1,500 feet in Great Britain, 

 while the rainfall is ample, and steady strong winds do not 

 prevail over large areas. On the contrary, the mild, moist 

 summer climate is infinitely better, and gives much greater 

 elasticity in the matter of selection of species than that of most 

 of the well-wooded European countries with their continental 

 climate of extremes. Gales, it is true, have made havoc of 

 extensive areas of forest, but any excessive damage in the 

 United Kingdom is ascribable to the way in which the forests 

 have in the past been grown and treated. This can, and would 

 be, removed once the study of forestry became more common, 

 and owners relied less on learning each by his own experience. 

 Forests are said to have been growing throughout the land 

 in the time of the Romans, and a study of local conditions and 

 the means of protection from wind should make the exclusion 

 of but little land necessary. 



Another not uncommon contention by writers on the British 

 afforestation question is that much of the soil apparently avail- 

 able is too poor for the growth of trees. As a matter of 

 fact this is never literally the case, for it is impossible to 

 conceive of a soil, with the exception of that of volcanic 

 origin, the composition or consistency of which prevents it 

 from sustaining some species of trees ; and thus where there 

 is sufficient soil, say one foot or more, the question immedi- 

 ately becomes which of a limited number of species suitable 

 is to be grown. Fortunately it is just the shallow or poorer 



