RESEARCH METHODS IN STUDY OF FOFEST ENVIRONMENT. 35 
ing, and the upper end should be capped, the suspending cord being 
attached to the inside of the cap. A welded pipe may be driven in 
almost any soil if the upper cap is screwed on tightly, and a mallet 
is used in driving, or wood is placed between the cap and hammer 
used. An iron hammer directly applied will tear the cap to pieces 
in a few blows. 
The conductivity of an iron pipe is so great that its use for soil 
temperatures at a depth of 1 foot or less introduces serious com- 
plications. Wood or porcelain tubes are therefore necessary. 
A porcelain wall tube, such as is commonly used in wiring build- 
ings, may ordinarily be obtained in lengths up to one foot or more 
at electrical supply shops. 
For a relatively permanent installation of thermometers at a 
depth of about a foot, wood tubes turned and bored in a wood- 
working shop are very satisfactory. The tube should have some 
taper, and the lower end should be pointed, so that it may be driven 
into a smaller hole that has been made with a bar. A wood which 
does not split readily should be used. When completed, the tube 
Fig. 1. — Sectional view of turned wood tube for soil thermometers at a depth of 1 foot. 
Telethermoscope (electric resistance thermometer) with one bulb and recording gal- 
vanometer $245 ; extra bulbs, each $15„ connecting wire, per foot about $0.10. 
and its plug should be boiled and cooled in a bath of creosote and 
linseed oil, to prevent swelling, shrinking, and cracking. The top 
of the tube may be turned with a slope outward, and the plug simi- 
larly turned, so that rain water does not enter readily. A tube which 
has proven very satisfactory in Forest Service work is shown in 
figure 1. 
A satisfactory tube for temporary use may be made by cutting a 
piece of 2 by 2 inch lumber 14 inches long, boring a 1-inch hole 
through from end to end, capping the lower end with a piece of 
tin, and cutting a plug to fit in the opening at the top. Two inches 
of the tube should be left above ground. It is hardly feasible to 
prepare this apparatus in greater lengths; in fact, for depths of 2 
feet or more, the iron pipe is to be preferred. 
In order to obtain reliable readings with a thermometer which 
must be lifted to read, it is necessary that the bulb of the ther- 
mometer be in some way protected from immediate contact with the 
air. This is clone either by placing it in a cork, by wrapping it in 
