72 
Yet its use insures, probably, a more thorough impregnation tban 
any of the other methods employed at present. It does not injuriously 
affect the strength of the wood, and requires a comparatively small 
outlay for plant. It can be started almost anywhere within a short 
time. 
Its drawbacks are that it can be carried on only during a compara- 
tively brief season; that it takes considerable time, although less than 
the steeping process ; and that it cannot be applied to square timber. 
Considering that the large quantity Of air which even fresh-Cut wood 
contains must necessarily obstruct the passage of the solution through 
the log and prevent the fluid from reaching every portion of the wood ; 
considering, moreover, that in pushing the solution through the ducts 
by pressure it was exposed to waste at every point where the ducts 
reached the surface, and that such; leaks were difficult to stop, I con- 
cluded to make an experiment to see whether better results could not 
be attained by reversing the Boucherie process, and applying suction 
instead of pressure for passing the antiseptic solution through the logs. 
Instead of using an elevated tank, I employed two small closed vessels ; 
in one of which a partial vacuum was kept up, while the other was 
being emptied of the sap and solution delivered into it by the pipe, 
which passed along the ends of the logs, and which was connected 
with the vacuum tanks, and by small rubber hose with the chambers 
formed at the head of each log. The caps, in this case, consisted of a 
thin, flexible metal ring, with sharpened edges. One edge was driven 
in near the circumference of the cut, and when firmly fixed, the disk, 
2 to 4 inches thick, which had been cut from the end of the log to pre- 
pare it for treatment, was driven into the other edge of the metal ring. 
This wooden bottom of the chamber was made air-tight by smearing 
clay or tallow over the outside face. 
A small knob fixed to the circumference of the metal ring contained 
a short tube, to which the rubber hose was attached by merely slipping 
it over the end of the tube. A cock in the short tube served to permit 
or to stop the exhaustion of the air from the chamber at the end of the 
log. The log was always placed so that the suction end was at a higher 
elevation than the end at which the solution entered the log. The in- 
troduction of the solution was managed in two different ways. In One? 
a chamber, identical with that at the suction end, was formed at the 
other end of the log, and the solution introduced into this chamber 
from a trough running along and 4 feet above the lower ends of the 
logs. This arrangement gave pressure at one end and suction at the 
other, thus greatly expediting the operation. Cuts of the fibers at the 
surface of the log, such as would be produced by chopping off branches, 
through which the air might be sucked, were readily detected and 
could be quickly stopped by rubbing clay or tallow into them. When 
the cock in the pipe connecting the suction chamber with the main pipe 
vas opened, the first result was that the air contained in the cells of 
