79 
wood, in i he form of ties, was IoiuhI to be 6.6 pounds; by 100 cubic, feel 
of oak, 5.5 pounds, and 5 pounds by 100 feet of pine moderately dry, 
containing a large amount of resin. 
On the Eastern railroads the strength of the solution at first was lin 
240 parts, and at present a solution of 1 in 99 is used. The timber is said 
to absorb about 2.G pounds per cubic foot, while Mr. J. B. Francis states 
that in the Lowell works the wood is found to absorb about G pounds of 
sublimate per 100 cubic feet. In England solutions have sometimes been 
used containing 1 pound in 46, but without securing as good absorption 
as was obtained with weaker solutions, since only 2.2 pounds per 100 
cubic feet were attained, it being probable that some of the sublimate 
was precipitated in the pores near the surface, stopping them sufficiently 
to partly prevent the entrance of the solution to the inside of the wood. 
The impregnation of wood with corrosive sublimate has always been 
carried on by steeping. In Germany wooden tanks, from 20 to 35 feet 
long and from 4 to 5 feet in height, are used. The rule observed as to 
the length of time of immersion has been to leave ordinary railroad ties 
ten days in the tanks, lumber five days, bridge timbers fifteen days. In 
some works the rule is to steep pine ties for eight days, and oak ties for 
fourteen days. 
At Lowell, Mass., where this process was introduced by Jas. B. 
Francis, C. E., in 1848, and has been carried on (with an interruption of 
twelve years, 1850 to 1862) up to this time, the steeping is performed 
in wooden tanks 50 feet long, 7i feet wide, and 4 feet deep. The rule 
laid down by Mr. Francis for the duration of steeping is, that the tim- 
ber should be kept immersed a length of time depending on its least 
thickness, one day being allowed for each inch in thickness, and one 
day in addition, whatever the thickness. This makes the time of im- 
mersion for a G-inch timber seven days. At the works of the Eastern 
Itailroad at Portsmouth, Me., tanks G9 feet by 9J wide, and G feet deep, 
built of granite laid in cement, are used. The inside of these tanks is 
coated with coal-tar, applied hot. Ties 6 inches thick, according to H. 
Bissell, M. M. W., Eastern Kailway, require one week ; 12-inch timber, 
two weeks. The time of immersion is, therefore, nearly the same at all 
works. The difference in thequantityof sublimate absorbed (2.6pounds 
per 100 cubic feet at Portsmouth, against G pounds per 100 cubic feet at 
Lowell and in Germany) could be due probably only to the fact that the 
timber treated at Portsmouth was not air-dried. 
Bichloride of mercury being a very active poison, great care in hand- 
ling it is plainly indicated. In Baden it was considered necessary to 
take extra precaution against the poisoning of the workmen, and some 
prejudice was created against this mode of preservation on this ac- 
count; but the experience in this country on this point is somewhat re- 
assuring. Mr. Francis states that, in an experience in Kyauizing, ex- 
tending over more than thirty years, he has known no case where themen 
operating with it have been made ill. He says that men working over 
the tank in which the corrosive sublimate was being dissolved in hot 
