[VoL. 7 
54 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
allowing water to flow through the siphon. From the vapor 
pressures of the dew-point and the temperature of the chamber 
the relative humidity is obtained. The pressure of aqueous 
vapor at various temperatures was secured by recourse to the 
Smithsonian physical tables (Fowle, '10). 
Method of weighing within the humidor.—The samples of wood 
shavings which were used to measure the imbibition of moisture 
from the atmosphere were planed as needed and placed in the 
wire baskets shown in fig. 1 and 2 of pl. 1. The baskets pro- 
vided with hooks were hung on two wires which were stretched 
across the chamber, one on either side of the openings in the top 
and the right-hand side of the chamber. Balances were in- 
stalled on the top of the humidor in such a position that a wire 
supporting a counterweight passed down through the opening 
leading to the chamber. The lower end of this wire is hooked so 
that the wire baskets can be hung upon the balance by means 
of a lever which passed into the opening in the right-hand end 
of the humidor. This operation can be performed without 
opening the chamber and thus changing the temperature and 
humidity within. The wire lever and the counterbalance wire 
are each provided with a cork, which can be slipped back when 
the device is in use or into the apertures when not in use. This 
device is an adaptation of that described by Dixon ('98). 
A similar one to that described by the writer has been used 
for the same purpose by Mr. C. H. Teesdale in charge of the 
Section of Wood Preservation at the Forest Products Laboratory, 
Madison. 
Determination of moisture content of wood.—After the samples 
of shavings had come to a constant weight in the humidor they 
were weighed and at the same time the relative humidity of the 
chamber was determined and recorded. The samples were then 
dried to constant weight in a dry-air oven at 100-105? C. The 
difference between the weight taken in the chamber and that 
after drying gave the total amount of moisture in the samples 
including that absorbed at the relative humidity of the chamber. 
The per cent of moisture absorbed was based on the oven-dry 
weight of the shavings. 
Determination of resin content of wood.—To determine whether 
the influence of a high resin content on moisture absorption can 
