RESEARCH METHODS IN STUDY OE FOREST ENVIRONMENT. 61 



positions that a near approach to a true catch will be secured. 

 Wind (81) is the factor which usually prevents all of the precipita- 

 tion of a given area from entering the gauge and which sometimes 

 removes snow from the gauge after being caught. To obtain pro- 

 tection from wind without obstructing the fall of precipitation from 

 any angle, should be the chief aim in the installation of gauges. 

 The ordinary rule is that the. edges of the shielding objects should 

 be at an elevation of 30° or less from the edges of the gauge. This 

 rule may be varied somewhat. Where precipitation is usually ac- 

 companied by high winds, the angle should be even less than 30°, 

 and the shield, to compensate, must be the tighter. Where pre- 

 cipitation is not so likely to be driven by wind, the angle may safely 

 be greater. A solid shield is less valuable than a partial one, be- 

 cause it may set up eddies in the air currents which will be fully as 

 unfavorable as the direct wind. On the whole, shields consisting of 

 trees or brush are best. 



Snow Depths. 



The depth of snow and its water equivalent will serve a useful 

 purpose in giving data on the period of dormancy for each forest 

 type, and in indicating the amount of precipitation available at the 

 beginning of the growing season, which in some localities may be 

 the larger part of the precipitation for the whole year (82, 88). 

 The period of dormancy might be obtained more exactly by tempera- 

 ture measurements, but the latter are not possible at present at 

 least on so large a scale. No data that can now be obtained will 

 cover the forest types of the mountain regions so completely as the 

 snow depth records, and the conclusions which may be drawn from 

 them, as to the water supply, will be extremely broad and com- 

 prehensive. 



Snow Scale Readings. 



The work of obtaining snow depth and density measurements by 

 the national forest ranger force, and in cooperation with the Weather 

 Bureau, is already well organized in some localities, and this work 

 is of a nature which may be done creditably by the general forest 

 forces. The same organization may possibly be effected with profit 

 in other localities. While the work was originally designed to fur- 

 nish data on the water available for stream flow and with that object 

 in view has been discontinued at the end of April each year, there 

 is no reason why it should not be slightly extended so as to serve 

 the purposes of any forest investigations. 



The general plan of the work is: 



1. To have ;< Large number of snow scales distributed over all the 

 main watersheds and throughout the entire range <>!' elevations and 



