PRESERVATION OF WOOD. 197 
have obtained a certain notoriety. Among these may be classed that of Kyan, 
who proposed to steep the wood in a solution of chloride of mercury, or to press 
the latter into it. So strongly had this method been recommended that the 
building of the Leipsic-Dresden railroad was deemed a suitable occasion for put- 
ting it to the proof. 'The superstructure of this road was formed, after the former 
' American system, of long wooden sills, strengthened by cross-ties, with iron 
rails attached, and these sills it was proposed to protect from decay by treating 
them in Kyan’s much-extolled manner, with an infusion of chloride ef mercury. 
The experiment, however, yielded a most unfavorable result. In the tirst place, 
the cost exceeded all expectation, amounting in the case of hard wood to $1,500 
per mile, and in that of soft to as much again. Moreover, the solution had 
penetrated the hard wood to the depth of but two or three lines, and hence the 
protection was highly problematical. It is true that by frequent treatment or 
by pressure a complete penetration of the wood might have been effected, but 
in that case the expense would have certainly countervailed every advantage. 
In England the same experiment has been tried with several railroads, and also 
with the pins used in the wooden pavements of London. 'Thesills of the London 
and Birmingham railroad were entirely decayed in three years, while those of the 
Great Western road, after six years, were still fresh and sound. These different 
results are attributable to the different modes of impregnation and to the con- 
tents of the respective liquids. The pins of the London pavement were found, 
after forty-six months, to be totally decayed. 
Dr. Boucherie, of Paris, has acquired much repute for his method of preserv- 
ing wood by means of copper vitriol, an expedient to which he was determined 
by long and sedulous experiment. So favorable were the results that, in 1856, 
after seven years’ experience, large contracts were made with him for the im- 
pregnation of the sills of railroads and posts of telegraphs. In considera- 
tion of important public services thus rendered, the jury of the great industrial 
exhibition of Paris, in 1855, on the concurrent recommendation of two sections, 
awarded to Dr. Boucherie a large medal, while the public authorities, on the 
same grounds, extended his patent five years beyond the limited time. The 
basis, as well as the scientific principle of his procedure, is supplied by the as- 
sumption of the circulation of the vegetable sap, the existence of the cellular 
tissue, and of tubes within the plank through which this cireulation is conducted. 
The second postulate is the possibility of displacing the sap and substituting a 
fluid possessing preservative properties. 
In 1838, Dr. Boucherie obtained a patent for a process which depended en- 
tirely on the circulation of the sap. Upon this first system, a tree with its full 
garniture of boughs and leaves was sawed off, and its lower end sunk perpen- 
dicularly in the fluid, which thus ascended with the sap to the top of the tree. 
This process, though satisfactory in a scientific point of view, was not adapted 
to practical use. It remained to discover some means of causing the conserva- 
tive fluid to penetrate intu the felled tree without recourse to the natural cireu- 
lation of the sap. Repeated experiments showed that it was practicable, by a 
high pressure, to expel completely the watery particles which remain for some 
time in the cells of felled trees, and to replace them by some other fluid. The 
problem was thus narrowed to the determination of a suitable fluid, and the 
application of a cheap and practical method of expelling the sap and introdu- 
cing its substitute. é 
After employing, experimentally, various antiseptic substances, Dr. Boucherie 
obtained the most satisfactory results with a solution of the sulphate of copper 
(copper vitriol) in water. This substance, when introduced, is destined to a 
two-told purpose—to expelthe sap, which is the cause of decomposition, and to 
fix itself in the wood. 
A small portion of the sap adhering to the inner walls of the cells is required 
for the fixation of the sulphate of copper; a combination of the two forms a 
covering which withstands external action, whether in the air, the earth, or the 
