350 . On Crystah enclosed in [^r^a^SeTisS' 
In preparing tlie specimens, so much of tlae substance must be 
added to tbe borax that it entirely dissolves at a bigb temperature, 
but is partially deposited when kept for some time at a heat below 
dull redness. The beads should be about ^h inch in diameter, and 
ird that thickness. The loop in the platinum- wire can easily be 
made circular by bending it round a glass rod. 
I need scarcely say that no one ought to expect to obtain good 
specimens at first. Much depends on that sort of manipulation 
which is easier to learn by experience than explain by writing. 
The most useful object-glass is a yVinch, of small aperture, 
made to adjust for looking through thick glass, so that crystals may 
be distinctly seen in the interior of the beads. When no condenser is 
used, the double convex form of the beads prevents our seeing more 
than a small portion of the interior ; but by using as a condenser 
a plano-convex lens, of about -J inch diameter and J- inch focal 
length, nearly the whole bead is well illuminated, without the 
definition being materially injured ; and even this may be overcome 
by properly regulating the distance of the condenser and the size 
of the aperture below it. The full beauty of the specimens can 
only be seen with a binocular microscope, and few objects are 
better fitted to show the advantage of that kind of instrument. 
The crystals then stand out in perfect relief, and are seen to be 
equally complicated in aU directions ; but I have selected as illus- 
trations those which lay flat, for the sake of simplicity. It must 
not be thought that in each case all the crystals are alike. Those 
formed on the surface difier much from those in the interior of the 
beads ; and in both positions, though the type is constant, the 
forms vary very considerably. 
After having obtained crystals of satisfactory character, if it be 
desirable to keep the specimen as a permanent object, the ring- 
shaped loop and enclosed bead should be cut ofi" and mounted in a 
cell with Canada balsam. This is requisite, since the moisture of 
the atmosphere causes the borax to become hydrated and opaque ; 
but, when properly mounted in balsam, it alters so slowly that I 
have not remarked any change after half a year. When thus 
mounted, the curved form of the beads almost ceases to be any 
impediment in examining crystals in the interior, and an ordinary 
achromatic condenser of long focal length may be used with advan- 
tage; but in some cases crystals on the surface are much less 
distinct than when the beads are not mounted. 
Few objects of the kind are more easily prepared than the 
crystals of borate of magnesia deposited from borax saturated with 
magnesia. They first form as thin prisms, and smaller crystals are 
afterwards deposited, so as to give rise to objects very much like a 
handle with a brush at each end, as shown by Fig. 1, , ^ 
