436 
GEOLOGICAL MANIPULATIONS. 
journey to Russia seems to have opened to him a vast field of observa- 
tion concerning living and fossil bears. 
Errata. — The printer, who, in my article for July, made mc s.ay that boric 
acid -was discovered in 1872 (instead of 1772) has, in composing the type of ray 
last contribution to the Geologist (at page 396, 4th note), made me aifirm that 
" Topaz contains mica,'' &c. The note should be, "Topaz, certain micas," &c., or 
better, " certain varieties of mica." 
GEOLOGICAL MANIPULATIONS. 
NOTES ON MAKING GUTTA-PEECHA MOULDS AND 
PLASTEll OF PARIS CASTS. 
By T. Rupert Jones, E.G.S. 
{To the Editor of tlie Geologist.) 
My dear Sir — As something towards enabling amateur and other 
geologists to communicate some of the results of their researches to 
their fellow-inqixircrs, I beg to offer the enclosed directions for making 
a preparation of gutta-percha and bees-wax, ranch better adapted for 
taking casts and moulds of fossils than gutta-percha itself ; and also 
some useful remarks for the preparation of plaster-easts. These direc- 
tions have been chielly drawn up, at my request, by my friend, Mr. 
John Wctherell, of Highgate. I have also to observe that the prepared 
gutta-percha is capable of being applied to the purposes of the museum 
in another way, which has been suggested to me by a friend lately. 
Thus, have some narrow slips of tin folded into squares, of convenient 
sizes, and into these press some of the composition, and use these as 
pedestals for such fossil shells, and other specimens, as will not 
stand steadily by themselves. By warming these pedestals in hot 
water, they are readily softened so as to receive the fossils when pressed 
into tliem, and the latter can be at any time raised for examination. 
Of course this composition, or even gutta-percha itself, is unfit foruso 
in hot cHmates, and for transmission, by post or otherwise, to the 
tropics. 
1. Freparalion of the gutta-percha — Procure a moderate-sized pipkin, 
into which put some bees- wax, place it on the fire, and allow it to melt 
(without boiling). Some fine cuttings of gutta-percha, which must bo 
free from any foreign substance, are then to be thrown into the pipkin, 
in the proportion of about four of gutta-percha to one of wax. The 
melted mass is then stirred up with a large metal spoon, until it is 
thoroughly mixed, free from lumps, and of an even colour. It should 
then be taken off the fire, and poured into a basin of warm water, to 
prevent its cooling too rapidly. In a few minutes it may be made by 
hand into convenient lumps for keeping. 
2. MaJdng a gutta-percha mould or cast — The prepared gutta-percha, 
above alluded to, is put into a saucepan of hot water — not boiling, as 
that would make it too sticky. After remaining a short time, it mny 
be taken out, and the softened part separated by the fingers, which should 
be kept moist to prevent the mass from sticking to them. This must bo 
i'cpcatcd until you have sufficient to cover the specimen which has to 
