4. BULLETIN 1136, U. S. DEPARTMENT OF AGRICULTURE | 
ture determinations by those who are accustomed to use it for other 
purposes. The formula for calculation follows: 
Moisture content in percent, _ original weight—oven-dry weight 
based on original weight aX original weight X100 (2) 
In the first of these systems the oven-dry weight is called 100 per 
cent; in the second, the original weight is so called. 
Although the system basing the moisture content on the original 
weight is not recommended for wood sections, conversion of moisture 
percentages from one system to the other sometimes is necessary. 
The following formulas permit such conversion: 
moisture content based on 
Moisture content based on oven- _ original weight (3) 
dry weight ~ 1—moisture content based on 
original weight 
moisture content based on 
Moisture content based on origi- _ oven-dry weight (4) 
nal weight ~ 1+moisture content based on 
oven-dry weight 
In these two conversion formulas, the values of moisture content 
must be expressed as decimals. -For example, if the moisture content 
of a piece of wood based on the dry weight is 25 per cent, and on the 
green weight 20 per cent, the formulas will read, respectively, as 
follows: 
Moisture content based onoven-___—0..20 0.20 
dry weight i {==0100 a8 O80 me 0.25 
Moisture content based on origi- 0.25 0.25 __ 0.20 
nal weight 71005 9 ieee 
BALANCES 
Any system of weights may be used for moisture sections, but the 
metric is more convenient than the others and is preferable for this 
reason. The unit weight of the metric system is the gram; a fraction 
of a gram is conveniently expressed as a decimal. 
The choice of a balance is largely a matter of service requirements, 
of personal preference, and of first cost. For general kiln use it 
should have a capacity of 200 to 250 grams and should be sensitive to 
0.1 gram. These requirements are met by the ordinary analytical 
balance in which the two pans are suspended from an overhead beam 
and which has separate weights; by the torsion balance, with its 
beams below the pans and with separate weights; and by the Harvard 
trip scale, which has the beam located under the pans and is provided 
both with separate weights and with a scale beam and rider reading 
to 10 grams by steps of 0.1 gram. (Pl. 1, A.) Kiln operators, how- 
ever, commonly prefer the multiple-beam balance, which has only 
one pan, suspended from the main beam, and which is provided with 
sliding weights. It has a normal capacity of 111 grams, with an 
auxiliary loose weight that nearly doubles this capacity, Agate 
