CONTINENTAL NOTES — FRANCE. 59 



is in the Emmenthal, some 30 to 40 kilometres (19-25 miles) 

 east of Berne. There are two valleys, each surrounded by 

 ridges forming nearly closed horseshoes, and down each flows 

 a stream. The two basins face the same way, south-west; and 

 the soil is similar. The basin called the Sperbelgraben is 56 

 hectares in extent (11 hectares between 900 and 1000 metres 

 altitude, 26 between 1000 and iioo, and 19 between iioo and 

 1200). The other basin, the Rappengrabli, contains 70 hectares 

 (i between 980 and 1000 metres, 23 between 1000 and iioo, 

 and 46 between noo and 1260). The slopes of the " thalweg" 

 (the main ravine) are, on the average, 20 % in the Sperbelgraben, 

 and 17-5 % in the Rappengrabli. The two basins are thus very 

 similar, but the side slopes of the former (which is the more 

 wooded) are somewhat steeper than those of the latter (with 

 little forest), so that topographically the Sperbelgraben favours 

 water-flow more than the other. 



The Sperbelgraben has 97 % of its area forest (silver fir 6, 

 spruce 2, beech 2 — 300 stems to the acre), 2^ % pasture, and 

 I % nurseries. The Rappengrabli has 35 % forest (spruce), 

 29 % heather with some scrub, 34 % grassland, and 2 % 

 cultivation. 



Very elaborate and careful arrangements are made for 

 measuring the flow of the streams — before, during, and after 

 rain. Observations are taken at periods of thaw, of short and 

 torrential showers, of prolonged rainfall, and of drought. 



In forest soils water sinks in and flows underground ; on 

 ground bare of trees it rushes off the surface. The rush is at its 

 maximum on grassy slopes. The influence of the forest on the 

 regime of the waters is chiefly due to the permeability and 

 porosity of its soil. Engler states, however, that it is not the 

 fact, as is generally supposed, that the flow of water is chiefly 

 checked by the great hygroscopicity of the covering of dead 

 leaves and mosses. This, of course, does absorb a great deal, 

 but once saturated it forms a quasi-impermeable mat over 

 which the water flows away. In spite of this, if the soil is not 

 frozen or previously saturated, a sudden thaw results in flood 

 far less in forest than elsewhere, and the flow of the stream 

 below is much less affected. The point which is not quite 

 clear in M. Huff"ers otherwise admirably lucid article is how, if 

 after the dead covering of the soil is saturated it shuts off the 

 percolation, the soil beneath can take up, as it is said to do. 



