436 



GEOLOGICAL MANIPULATIONS. 



journey to Russia seems to have opened to him a vast field of observa- 

 tion concerning living and fossil bears. 



Eeeata. — The printer, who, iu my article for July, made me say that boric 

 acid Tvas discovered in 1872 (instead of 1772) has, in composing the type of my 

 last contribution to the Geologist (at page 396, 4th note), made me affirm that 

 " Topaz contains mica," &c. The note should he, " Topaz, certain micas," &c., or 

 better, " certain varieties of mica." 



GEOLOGICAL ITAKIPULATIONS. 



KOTES Olf MAKING GUTTA-PEECHA MOULDS AHD 

 PLASTER OE PARIS CASTS. 



Py T. Rupeet Jones, E.G.S. 



{To the Hditor of the Geologist.) 



My deae Sir — As something towards enabling amateur and other 

 geologists to communicate some of the results of their researches to 

 their fellow-inquirers, I beg to offer the enclosed directions for making 

 a preparation of gutta-percha and bees- wax, much better adapted for 

 taking casts and moulds of fossils than gutta-percha itself ; and also 

 some useful remarks for the preparation of plaster-casts. These direc- 

 tions have been chiefly drawn up, at my request, by my friend, Mr. 

 John Wetherell, 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 vray, 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 them, and the latter can be at any time raised for examination. 



Of course this composition, or even gutta-percha itself, is unfit for use 

 in hot climates, and for transmission, by post or otherwise, to the 

 tropics. 



1. 'Preparation of the gutta-percha — Procure a moderate-sized pipkin, 

 into which put some bees- v\^ax, place it on the fire, and allow it to melt 

 (without boiling). Some fine cuttings of gutta-percha, which must bo 

 tree 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. Making a gutta-per<-ha mould or cast—^hQ prepared gutta-percha, 

 above alluded to, is put into a saucepan of hot water — not boiling, .'is 

 that would make it too sticky. After remaining a short time, it may 

 be taken out, and the softened part separated by the fingers, which should 

 bo kept moist to prevent the mass from sticking to them. This must bo 

 ^•t'pcated until you liave suliloient to cover the specimen which has to 



