PROCEEDINGS OP GEOLOGICAL SOCIETIES. 
437 
bo operated upon ^vith a thin coating, not exceeding the sixteenth of 
an inch. Having obtained a smooth even surface of the gutta-percha, 
warm the specimen by dipping it into warm water, or otherwise, and cover 
it with the preparation. It is advisable sometimes to wet or oil the 
specimen previously to putting on the gutta-percha, to prevent it ad- 
hering. It must now be well pressed on the specimen, in order that it 
may delineate the more delicate structure, and this manipulation must be 
contiuued until it becomes hard ; then remove it from the specimen, or, 
if necessary, cut it with an oiled knife. Previous to cutting, marks 
should be made, to ensure the mould beiug correctly joined in taking 
the plaster-cast. It is desirable to make a small hole in one of the 
pieces, to allow the plaster to be poured in. 
3. Maldng the pJmter-cmt : — Sprinkle the plaster into a basin con- 
taining water enough to fill the required mould. Mix it well until it 
forms a thick paste ; it is then fit for use. 
Take the pieces of the gutta-percha mould, and join them by means 
of India-rubber bands, exactly according to the marks previously made. 
A small quantity of plaster is then poured into the opening, and the 
mould is turned round several times. This must be done quickly, as the 
plaster dries very rapidly. More plaster is added until the mould isfull. 
It is then left for a few minutes to set. The mould is then taken off, 
and well cleaned, to be ready for another easting. The tools should be 
put into water immediately after using them, to prevent the trouble 
which otherwise arises from the hardening of the plaster. 
In taking a plaster-cast from a large open gutta-percha mould, after 
carefully oiling the surface of the latter, the moist plaster should be first 
poured on in a fluid state, and carefully and quickly worked iuto all the 
irregularities of the surface by means of a stiff brush; a shortened 
" painter's tool" is best for the purpose ; and the plaster subsequently 
added should be cautiously and continuously jogged, holding the mould 
between the hands, and knocking its base on the table with steady, 
slight successive blows, so as to ensure the bubbles of air leaving the 
mould, and rising to the top of the plaster, as long as it is fluid. 
It is often advisable to place the ends of a piece of folded string in 
the soft plaster whilst making the cast, to supply means of pulling at 
the cast to release it from the mould, 
London, August 23rd, 1858. 
EEPOETS OF THE PEOCEEDINGS OF GEOLOGICAL 
SOCIETIES. 
East Kent Natural IIistokt Society. — Tlio East Kent Natural History 
Society held tlieir annual meeting on the 28th of August, and selected Dover as 
their head-quarters upon the occasion. The Association has been in obscure 
existence some years, but appears to have been lately revived -witli great vio-our 
and we hope vrill long continue to labour earnestly and well in a district in which 
much as has been done, so much yet remains to do. 
The arrangements of the day comprised the double attraction of an excursion in 
the morning and a dinner in the evening ; the scene of the first portion of this 
programme being the coast lying between Folkestone and Dover. The gatheriu'r 
was further favoured by splendid weather, and by every other external circurn^ 
stance which could contribute to ensure its complete success. 
