538 Progress in Sctence. (October, 
A flame is held over the orifice, and at the moment the evolved vapour is 
ignited the temperature of the fluid is corredily indicated by the thermometer. 
In ascertaining specific gravities by this instrument, a hydrometer is also 
placed within the glass cylinder in such a manner that its scale-tube is free to 
move up or down through a hole in the brass cover. The surface of the fluid 
tested is plainly visible through the glass cylinder, and the scale may be accu- 
rately read. 
A so-called rubber-graphite paint has recently been patented, said to be 
waterproof and to present other advantages of reducing the corrosive influence 
of exposure to the atmosphere, &c. It is a solution of pure india-rubber in 
linseed oil, which is ground with graphite into a thick, elastic, smoothly- 
flowing paint. Compositions of which india-rubber forms a part possess, in a 
very high degree, the quality of resisting the action of moisture and of corrosive 
gases. The graphite is a pure form of carbon; and it is well known that 
paints containing carbon in form last longer than other kinds, holding their 
body and colour when other paints are totally destroyed. So that the com- 
bination may, as suggested, form a paint of great durability and highly- 
protective qualities. Cream colour or drab paints can be obtained by this 
method. 
An admirable paper on the preservation of wood has been written by 
M. Hermann Haupt, C.E. in an American contemporary. The experiments 
show—That so long as the celts of wood are occupied by air and moisture, no 
preservative solution can be introduced, and the expulsion of air and water must 
be the first step in any effective process for preserving timber from decay. 
That water can be expelled by a long-continued application of heat, but air 
only by expansion in a vacuum, and the combination of heat and vacuum will 
secure the most rapid expansion both of water and air. The preservative 
fluid must be introduced while the cells are empty, consequently the process 
must be carried on im vacuo. ‘That no pressure, however great, applied ex- 
ternally to the surface of timber, can force fluid into the interior so long as 
air or water is contained in the cells. When air alone is present, there may be 
penetration to a limited extent, superficially, but water is practically incom- 
pressible. If, however, the pressure is applied at one end only of a log, as in 
the Boucherie process, a fluid may be forced through and exude from the other 
end. An apparatus to fulfil the conditions which, from the preceding dis- 
cussion, appear to be essential to success, must be founded on a process 
similar to distillation in vacuo. It must consist of at least two vessels—one 
a receiver corresponding to a retort, in which the material can be placed and 
subjected to the action of heat; the other a condenser, in which all escaping 
vapours can be condensed, and the vacuum maintained during the process in 
both vessels. The condenser may be of much smaller capacity than the 
receiver ; they should communicate by pipes furnished with stop-cocks, and 
both be supplied with thermometers, vacuum gauges, and pumps. Asan illus- 
tration, suppose wood is to be impregnated with dead oil or ony other fluid. 
The receiver must be filled with the wood to be operated on, the door closed 
air-tight, and the air expelled from both the receiver and condenser. The ex- 
pulsion of the air may be effected in various ways. Steam may be admitted at 
one end to drive out the air at the other end; the subsequent condensation of 
the steam should leave a vacuum, but in the experiments of the writer this 
plan has been only partially successful. The air may be exhausted by an air- 
pump, but a perfect vacuum cannot in any way be secured. The vessels may 
be filled with water, and the water removed by a pump below the level of the 
bottom into which the water flows. This should remove all the air excepting 
that which escapes from the cells. As the atmosphere supports a column of 
water 33 feet high, pipes may lead to a tank at a level about 40 feet lower, 
where the location is favourable, and thus by filling the vessels with water and 
opening cocks to allow the water to flow by gravity into the tank, a very 
perfect vacuum could be produced. This arrangement would be particularly 
favourable for maintaining a vacuum in the condenser; a pipe in the condenser 
could throw jets of water in spray from numerous fine perforations, and the. 
