62 EFFECTS OF FORESTS ON HUMtDlTT. 



**M. Mathieu, sub-director of the Forest School, has uniertaksa a 

 series of experiments under vsry favourable conditious. Of these the 

 foUowia^ is one wbioh is pirtioularly intorostia^, and one, the results 

 obtained by which scarcely agree with those of Mirshal Vaillaut. 

 Two udom^tres were placed at the forest statiou of Ouiq-TranchSes, 

 the one in the open wood, under a patch of beeches and hornbeims, 

 of average denseness, and of the age of 42 years ; the other, at a 

 little distauce, iu the middle of an opea space many hectares ia 

 extent. It may be well to note tliat the forest udom^tre is of special 

 construction; that the receiver embraces the stem of one of the 

 perches of the clump, and presents a surface quite equal to the 

 projectioa of the top of the tree ; tliat by this means the indications 

 of the instrument are quite exact, and represent well, without 

 exaggeration or diminution, the depth of tlie sheet of water received 

 by the wooded ground ; and that this water, dropping from leaf to 

 leaf, passes through them, or flows down the trunk. 



" Under these conditions the udomHregave, in 1853, the following 

 quantities of rain : — 



MEASUREMENT OF RAIN. 

 Monthg. Under wood. Outside wood. Proportion. 



miliim^tres. mm. mm. 



January, 68 73 0-931 



February, 37 36 1-025 



March, 50 50 1 



April, 69 73 -945 



May, 8 8 1 



June, 48 52 -923 



July, 31 34 -911 



August, 26..... 37 -702 



September, 59 61 -962 



October, 118 122 -967 



November, 26 28 -928 



December, 163 174 -936 



Total, 703 749 -939 



" It may be astonishing to see in the table that during the months 

 of February, March, and May the sheltered pluviomfetre received as 

 much or more rain than the pluviomatre in the open space ; it is 

 necessary to consider that, either through some caprice of the rain, 

 or by some such effect of the trees, there fell more water in the wood 

 than in the adjacent open space. This result, moreover, might 



