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SUGGESTIONS AS TO COLLECTING 
such as Foratuinifera or Sponge-spicules scattered through it; and 
they may be obtained by levigating the loose powder, or, where the 
material is silicified, by treating it with dilute acid. 
5. Ploughed fields, or fields in the autumn when the crops have 
been gathered, frequently yield fossils in those instances in which 
limestone or other rocks are near the surface. Molluscan and other 
shells and many other calcareous fossils often become silicified, and 
are thus rendered more durable than the limestone matrix ; and 
they remain when the rest of the rock has been dissolved. Thus it 
happens that nodules and stones picked from the surface of fields 
ior the repair of roads, etc., often contain good fossils; and heaps of 
such materials by the roadsides will repay careful scrutiny. 
Treatment of Fossils in the Field. 
1. As a general rule, it is best to do the least possible trimming 
and cleaning of a fossil in the field. Final preparation for the 
cabinet can be far better done at leisure afterwards. 
2. Large triable specimens, such as vertebrate skeletons, large 
Ammonites, or groups of shells, in a matrix which is only moderately 
hard or liable to fall to pieces on drying, need special treatment. 
The fossil ought to be first carefully uncovered as it lies in the rock. 
Then thin paper may be gently pressed over, covering the whole, and 
as far as possible filling every crevice. Next, plaster of Paris must 
be poured over this prepared face, and allowed to harden in a moder¬ 
ately thick layer. Finally, the specimen may be excavated and 
transported as a slab, the plaster covering serving as an adequate 
support. N.B.—If paper be not used, the plaster cannot be readily 
removed from the fossil, and may completely damage it. 
Strips of wood, or thin iron rods, fixed down to the specimen by 
plaster of Paris and string, may be used, to give rigidity to friable 
or heavy specimens in lifting them from the quarry to a waggon for 
transport. 
o. Some large specimens— e.g. bones in Pleistocene deposits—need 
to be hardened before removal from the matrix. This can be done 
by uncovering the upper face of the fossil, and pouring slowly upon 
it a warm, weak solution of gelatine or glue, or the preparation 
