132 NOTES TO THE 



Eothschild, Editeur, 13, Eue des Saints Peres, Paris) on the 

 Anatomy and Physiology of Bees, by a Russian engineer, Mr. 

 Michael Girdwoyn. The drawings are marvellously beautiful. 

 Every one interested in bees should have a copy of this work, 

 which costs thirteen or fifteen francs. 



EFFECTS OF TREES ON RAINFALL, p. 201. Mr. Menzies, 

 Deputy Surveyor of Windsor Forest, writes me thus : 



"Mr. White has entered upon one of the most abstruse ques- 

 tions of forest economy, to which much attention has been given 

 since his time. The only time when trees do truly perspire is 

 in the summer, when some kinds, such as notably the oak and 

 beech, distil a sort of dew from their leaves. It is quite true also 

 that they prevent evaporation from the surface of the ground, 

 and so have a tendency to prolong the supply of water that any 

 district may yield ; but on the other hand they themselves are 

 great drinkers of the water in the subsoil, and so again they 

 diminish the store. Whether these two tendencies coimter- 

 balance one another, or whether trees favour the storage of water 

 most, has by no means been settled. Practically no one would 

 think of surrounding a reservoir of pure drinking-water with 

 trees ; because the falling foliage injures the water, and the 

 effects of trees, in condensing water which is present in the 

 air, are infinitesimal. Any account given by travellers of the 

 diminishing of streams in any country in consequence of the 

 denuding of the district of trees must be received with extreme 

 caution just as we know that we must be guarded in receiving 

 from people of this country stories of the extremely cold winters 

 and hot summers which used to prevail in their youth. The 

 statistics of rainfall have only been collected in England within 

 the last ten years with anything like scientific accuracy, and in 

 other parts of the world the science is quite unknown. Hence 

 we have no real data to go upon, and without a series of actual 

 gaugings of the streams extending over a number of years, a truly 

 valuable opinion cannot be formed. Since Mr. White's time 

 many thousands of acres in England have been cleared, and 

 many thousands have been planted, but no data exist to form 

 any reliable opinion as to the effect, if any, upon the rivers ; and 

 such data would become vastly complicated, as it would be 

 necessary at the same time to consider the effect of the agri- 

 cultural drainage and the formation of canals, &c., that have 

 been done since his time. My own opinion is that in England 

 the trees have had no effect one way or the other. I have read 

 many accounts of the effect, in other countries, of large forests in 

 condensing the moisture on the hills, and the balance of evidence 



