48 THE MEDALS OF CREATION. Cuar. IIT. ~ 
cliffs, and of Walton in Essex, are friable, and apt to split 
and separate in the direction of the vertical plates of den- 
tine and bone: the pieces should be glued together, and 
when set, the tooth be thoroughly saturated with thin glue, 
used very hot, and the superfluous cement removed with a 
sponge wrung out as dry as possible from boiling water. 
If there be any portion of the jaw attached to the teeth, it 
must be carefully preserved; and search should be made 
for fragments of the articulations, or parts of the joints and 
sockets. 
In argillaceous strata, as the Lias-shale, London Clay, &e., 
the fossils are frequently saturated with brilliant pyrites, or 
sulphuret of iron ; a mineral which decomposes upon expo- 
sure to the atmosphere, and occasions the destruction of the s 
specimens. The fossils of the Isle of Sheppey are peculiarly } 
obnoxious to this change. 
The remains of vertebrated animals in the Lias, very 
often occur as skeletons more or less perfect, the entire con- 
figuration of the original being preserved in many instances 
(Bd. pl. 7. Petrifactions, p. 340). But the deposit in which 
they lie is generally laminated, and the shale flakes off with- 
out great care; much time, labour, and practice are therefore 
required, to obtain specimens of any considerable size. To 
the late Miss Mary Anning, of Lyme Regis, the merit is due, 
of having first accomplished this difficult task ; Mr. Hawkins 
has subsequently carried the art to perfection, as may be 
seen in the marvellous examples of Ichthyosauri and Plesio- 
sauri, in the British Museum.* 
The small specimens, such as the detached paddles, groups 
of vertebree and ribs, &c., that are likely to come under the 
collector’s notice in his personal researches, are not difficult 
of preservation. Mr. Hawkins employed a strong watery 
solution of gum arabic as the cement, and plaster of Paris 
as the ground, using shallow wooden trays of well-seasoned _ 
* Petrifactions, Room IV. chap. iv. pp. 341, 376. 
tot Fee 
