12 BULLETIN 87, U. S. DEPARTMENT OF AGRICULTURE. 
tighter than where unseasoned lumber is used. The power used for 
operating the small mill to cut out the necessary timber and lumber 
to construct a flume is usually the ordinary portable type of boiler 
and engine, sometimes in the combined form. There will be found 
cases and localities in which the use of an overshot or an undershot 
water wheel will more economically furnish the necessary power, 
where there is an ample supply of water and favorable conditions for 
x ts being used for this purpose, and there will be some cases in which 
electric power to operate the mill, transmitted from a convenient 
line of some electric-power plant, will be found most economical. 
After the mill is installed it is advisable to use prepared frames, 
"forms," or miter boxes in cutting the brackets, frames, or arms 
with the " power saw" into the desired length and shape, and also 
in cutting the braces, stringers, sills, overla}'s, and material for use 
in trestling. Experience has demonstrated that the material can 
be shaped at the mill and transported to the p]ace where it is to be 
used by means of the water in the flume much more economically 
than in any other manner. It is advisable to prepare the frames 
and arms at the mill ready for setting up, and flume them in their 
finished form down to the point where they are to be used; this 
method requiring only that they be placed and fastened in position 
after arriving there. (Fig. 5.) 
A CAREFUL SURVEY NECESSARY. 
An accurate and careful survey of the proposed line of flume con- 
struction is a prime necessity and often a great economy. A need- 
lessly expensive survey should always be avoided, but accuracy of 
grade and careful and reliable "leveling" is imperative in order to 
insure lasting flume construction. The equalization of grade is very 
advisable wherever it can be accomplished without too great an 
expense. And right here a practical knowledge of the comparative 
benefits to be derived from having a steady or an even and moderate 
grade, considered in relation to cost, is of great value. The grading 
of soil in knolls or hillocks or ridges along the prospective flume line 
is advisable up to a certain point, if necessary to maintain a reason- 
ably steady grade for the flume. A careful preliminary survey fol- 
lowed by a location survey, using a transit and level, will make it 
possible to obtain a reliably constructed profile map which will show 
to the prospective operator what the grading should be at different 
points of his line. It is always best to know just what the grade 
is going to be when completed, and approximately what it is 
going to cost, before starting the construction work. No detailed 
estimate of the cost of survey is included here, for the reason that 
the wide range in conditions where flumes might be constructed 
would make any set figures unreliable and possibly misleading. A 
