84 
covering tbe ties, Avhere they touched the rails, with coal tar, and by 
using; galvanized spikes. Sulphate of copper is less hygroscopic than 
chloride of zinc, and ties treated with it are more liable to crack. 
There is one point, however, in which it is superior to chloride of zinc, 
and which is of very great importance, when the treatment is to be 
effected under contract. While it is difficult to control the strength of 
a solution of cbloride of zinc used in impregnation, or to find by chemi- 
cal analysis the actual quantity of zinc contained in the timber after 
impregnation, both of these operations can be performed with great 
accuracy, and without much expenditure of time or money, when sul- 
phate of copper is used. There can be less cheating, and, therefore, 
the success of the treatment as a means of preservation is more fully 
assured. To show the efficiency of the sulphate of copper in prolong- 
ing the life of wood, it may be stated that, according to German experi- 
ments, 60,000 fir ties which had been merely steeped in a solution of 
sulphate of copper lasted on an average 13.0 years ; that 36,000 ties of 
the same kind of timber, which had been boiled in a solution of this 
same antiseptic, and laid on the Berlin, Potsdam and Magdeburg Kail- 
road, lasted on an average 14 years ; and that 111,000 fir ties, impreg- 
nated with sulphate of copper under pressure, averaged 16 years of 
usefulness; while unimpregnated fir ties used in the same railroads 
lasted only from 7 to 9 years. It may, therefore, safely be assumed 
that the durability of such ties would be doubled by proper treatment 
with sulphate of copper. 
The use of sulphate of copper has been nearly abandoned in France, 
but is still carried on by some of the German railroads. 
In this country it has been used only in connection with the Thilmany 
process, which will hereafter be described. One obstacle to its use may 
have been found in the fact that sulphate of copper formerly cost much 
more than chloride of zinc ; but the price of copper has declined so much 
of late that the difference in cost has been greatly reduced. 
Note. — The outfit for the Boucheric process is light and inexpensive, as well as that 
for Kyaniziiig, consisting of tanks in which to mix aud store the preserving liquid and 
troughs to receive the sap ; or, with the latter process, tanks in which to soak or steep 
the timber. The Burnettizing process and the Bethel] process must prepare tbe wood 
by steaming, etc., aud require iron cylinders, a steam boiler, aud pumps. But the 
usual form cau he modi lied, as Colonel Flad has indicated, by using two or more 
smaller cylinders with boiler and pumps, all attached to trucks or arranged to he 
easily handled, aud with all pipe connections so arranged as to be made or broken 
readily. 
The advantages of a movable plant have received less attention and have been 
tested less than they deserve. Tbe transportation of timber is of course a consid- 
erable item of expense. A plant of moderate size could he taken to the various 
sources of supply from which the timber comes or to the most economical distribut- 
ing points, and thus the cost of transportation, in one direction at least, would often 
be saved. — H. C. 
