158 PREPARATION AND MOUNTING 
“The nitre is thus polished on both its surfaces, which 
should be brought as near as possible to parallelism.” 
Some sections of the naturally formed crystals also show 
the “rings” very well,—as Iceland spar, which gives a 
single ring and cross; but the difficulty of cutting and 
polishing them is almost too great for the amateur, and 
must be left to the lapidary. This curious phenomenon, 
however, may be seen by using a plate of ice smmmavine"s: 
formed of about one inch in thickness. 
Before concluding these remarks on sections, I must men- 
tion a few difficulties which may be met with, and their 
remedies. The foremost of these is the softness of some 
objects, which have not resistance enough in themselves to 
bear cutting even with the sharpest instruments. This may 
often be removed by soaking in a solution of gum, and then 
drying, which will render the substance firm enough to be 
cut, when the sections must be steeped in water, and the 
gum thus removed. Small seeds, &c., may be placed in 
wax when warmed, and will be held firmly enough when it 
is again cold to allow of them being cut into sections.* 
And, lastly, where a substitute for a microscopist’s hand- 
vice is required, a cork which fits any tube large enough 
may be taken and split, the object being then placed between 
the two parts, and the cork thrast into the tube, a sufficient 
degree of firmness will be obtained to resist any necessary 
cutting. 
* Mr. T. K. Parker informs me that he uses paraffine as an ‘‘ ob- 
ject-support ” when sections are required, as follows :—‘‘ The mixture 
use for embedding objects consists of solid paraffine (ordinary paraf- 
fine candles will do very well) melted down and mixed with a little 
paraffine oil, without which the paraffine is too hard to be easily cut. 
The mixture when cold is cut into suitable pieces, a hole is scooped 
out in the centre, the object to be cut placed in it, and a little of the 
melted mixture poured round it. Thé sections are cut with an ordi- 
nary razor, which, as well as the object, must be continually wetted 
with spirit. This method is useful for all objects which are either too 
small for the hand or too soft or brittle to be cut in the ordinary way. 
is especially useful for histological specimens, leaves, embryos, 
re, ” 
