18 
On the Preservation of Timber. 
Silicate of soda, 
Sulphate of iron. 
Another series of sleepers were first saturated with a solution 
of green copperas, or sulphate of iron, and then treated with solu- 
tions of materials named below : — 
Shumac, 
Arsenious acid, 
Gas water. 
I further tried a solution of chloride of barium alone, and 
afterwards decomposed it in some of the sleepers, by means of an 
alkaline sulphate. 
Another set of sleepers were impregnated with a solution of 
chloride of calcium, which were further treated with solutions of 
Carbonate of soda, 
Sulphate of soda. 
I also tried arsenious acid alone in solution, and combined it 
afterwards, in some of the same sleepers, with sulphur, which I 
employed in solution in the form of sulphuretted hydrogen, 
I likewise tried a solution of glue, which I endeavoured to 
render insoluble in the pores of the wood by the subsequent 
action of shumac. 
I also treated some sleepers with a solution of shumac. 
Old Sleepees. — When I had reached this point, and during 
a journey to York, I noticed the piles of old or waste sleepers 
accumulated at different points along the line ; and it occurred to 
me that it might be possible to convert them to some useful 
purpose. On returning to Newcastle, instead of continuing the 
series of experiments, in which I had intended to try various 
preparations of manganese, bi-carbonate of lime, &c., I made an 
examination of some old sleepers. 
The result of that examination led to the adoption of that 
process which I have now to detail, and in prosecuting which I 
had the benefit of the excellent advice of Mr. Browell. 
Considerations in the Choice of Materials. — In all the 
experiments related above, I was guided in the choice of my 
materials by the considerations of their effect in increasing the 
durability of the timber, the facilities they offered in their appli- 
cation, the first cost in some measure dependent on the extent of 
their consumption, and, lastly, on the market for a present and 
future supply. 
I believe it can scarcely be affirmed of any of these substances, 
that they meet all these conditions, although many of them are, at 
present, what may be termed waste manufacturing products. 
