THE PRESERVING OF TIMBER FOR ESTATE PURPOSES. 83 
which the timber can be placed in position and withdrawn, permits 
of a greater quantity being dealt with in a given time than when 
it is placed by hand into the receiver. 
The proportion which the quantity of timber in each charge 
bears to the total capacity of the receiver varies with the size and 
form of the timber, and the manner in which it is stowed, but may 
be stated as being approximately 75 per cent. on the average, for 
such timber as railway sleepers. The timber requires to be loosely 
packed when placed in the receiver, so as to permit the creosote to 
have free access to every part of its surface. 
The creosote is stored in a tank (or series of tanks) placed below 
the level of the receiver, so that the latter may drain into it. The 
storage tank may be constructed either of wood or iron, and for 
convenience is usually sunk into the ground immediately below 
the receiver. The tank requires to be large enough to contain 
sufficient creosote to fill the receiver after the timber is placed in 
it, as well as the quantity required for injection into the wood in 
the process of creosoting. 
As the naphthaline contained in the creosote becomes solid at 
ordinary temperatures, it is necessary to raise the temperature of 
the oil to 120° Fahrenheit, in order to dissolve the naphthaline, 
and render the creosote perfectly fluid. This is effected by means 
of pipes of cast or wrought iron laid in the tanks, through which 
steam circulates from the boiler of the steam-engine attached to the 
apparatus. Similar pipes are sometimes laid inside the receiver, to 
keep the creosote from cooling down too quickly in cold weather. 
From the lowest point of the receiver, a pipe, provided with a 
stop valve fixed at a convenient place, is led directly to the creosote 
tank. This pipe serves the double purpose of conveying the creosote 
to the receiver, from which the air has been exhausted, and of 
draining the surplus creosote from the receiver back to the tank 
when the process of injection 1s completed. 
The receiver is connected by other pipes, each having a stop 
valve, to an air-pump, and to a force-pump, both driven by the 
steam-engine which works the whole apparatus, and it is also pro- 
vided with a safety valve, a vacuum gauge, and a pressure gauge. 
The timber having been placed in the receiver, the end door is 
closed and securely bolted up, a suitable packing being used to 
make the joint air-tight; the valves on the connecting pipes, 
except that leading to the air-pump, being at the same time closed. 
The air-pump is started and kept going until the air is exhausted 
