OF MICROSCOPIC OBJECTS. 153 
Coinciding with this opening is a brass tube, fixed in the 
under side of the table (if it may be termed so). This tube 
is so cut at the bottom as to take a fine screw. Another 
screw is also placed at the same end of the “ table,” which 
works at right angles to this, so that any substance in the 
tube may be wedged firmly by working this last screw. To 
use this instrument, the piece of wood or other object of 
which a section is required must be placed in the tube, 
when, by turning the screw underneath, the wood is raised 
above the brass plate more or less as wished, and by using 
the screw at the end, itis held firmly in the same position. 
With a flat chisel the portion of the object which projects 
above the surface of the brass plate may now be cut off, and 
by means of the bottom screw another portion may be 
raised and treated in the same manner. As to the thickness 
of which objects should be cut, no proper directions can be 
given, as this differs so greatly that nothing but experience 
can be any guide. The same thickness can be obtained by 
working the screw underneath in uniform degrees, the head 
being marked for this purpose; and where the substance to 
be cut is very much smaller than the hole in the brass plate, 
it may be wedged with cork. 
*As this instrument is peculiarly adapted for cutting 
wood (though used for other substances, as before men- 
tioned), I shall notice a few particulars concerning this 
branch of sections. It may here be remarked, that to 
obtain anything like a true knowledge of the nature of 
wood, it should be cut and examined in at least two direc- 
tions, across and along. ‘The piece of wood is often placed 
in spirits for a day or two, so that all resinous matter may 
be dissolved out of it; it must then be soaked in water for 
* M. Mouchet, in order to avoid all danger of ‘‘ beards” in cutting 
wood sections, procured a knife with a semicircular blade. This was 
fastened at the end upon a flat plate, in order to revolve, as we may 
call it, the handle being long enough to give leverage for any required 
power. The wood supporter being placed in a favourable position, 
the knife is easily brought round, and the section cus by a circular 
action. 
