69 
of wood is such that, wM\h it oilers but slight resistance to the flow of 
liquids through its longitudinal ducts, it is very difficult, even, under 
great pressure, to force any liquid from the surface to its center, at right 
angles to the direction of the fibers. Hut the entrance of any preserv- 
ing liquid through the ducts and other cells is resisted by the sap re- 
maining in the wood and by the air which fills the cells not occupied 
by sap, so that steeping, as generally carried out, causes the antisep- 
tics to penetrate but a short distance from the surface of the wood. 
It is evident, therefore, that wood which is to be preserved by this 
method of impregnation should be fully framed to the exact form in 
which it is to be used before it is treated. 
Steeping may sometimes be useful as a process preparatory to others. 
(2) The Boucherie Process. — About 45 years ago Boucherie, a French 
chemist, conceived the idea of impregnating wood with a preserving 
fluid, by introducing it into a living tree through a groove cut around 
its surface near the ground, from which it was to arise, together with the 
sap, through the cells of the wood. 
But this was soon found impracticable, and in 1841 Boucherie pat- 
ented a process for preserving wood by forcing a solution of sulphate 
of copper through the cells of the wood under hydrostatic pressure ap- 
plied at one end of freshly cut and unbarked logs, so as to remove the 
sap and replace it by the solution of copper. Since then impregnation 
with sulphate of copper lias been generally known as the ''Bouche- 
rie process," although this term is more properly applied to the method 
of impregnation invented by him, which may also be used in connec- 
tion with other preservatives as well as with copper. 
To secure the ready percolation of the fluid through the cells of the 
wood it is necessary that the sap of the wood to which the process is to 
be applied should possess the greatest possible degree of fluidity. This 
it has during the first months of the year. Timber cut during the au- 
tumn may also be used, although the sap at that season is more viscous 
and less readily removed. During the spring and summer the sap con- 
tains so much gummy extractive matter that it is not fit for treatment 
by this process. The timber is treated in the form of round logs, wdth 
the bark left on. The treatment should be applied as soon as possible 
after the timber has been cut. When exposed to the action of the at- 
mosphere, even for a short time, the. sap . will solidify aud greatly retard 
the process. It is customary, therefore, to cut the logs of somewhat 
greater length thau that ultimately required, and to saw off a few inches 
from the ends just before subjecting the logs to the process. 
Logs which are placed in clear water immediately after they are cut 
will remain for some time in proper condition for treatment. If the logs 
are intended for railroad ties they may be cut of suitable length to make 
either one or two ties, and the mode of introducing the solution varies 
accordingly. Logs cut for siugle length treatment are placed (with a 
