276 THE MEDALS OF CREATION. Cnap. VII. 
the tropics, and increases the local temperature of the sea 
in those localities.* 
On Cottectine Foss, Corats.—Few instructions are re- 
quired for the collection of fossil zoophytes ; for as the most 
important characters of the several kinds have been pointed 
out in the previous descriptions, the student will be able to 
select illustrative specimens for his cabinet. The minute 
corals, &c. of the Chalk, and other limestones, are to be ob- 
tained by the same process as that directed for the discovery 
and preservation of the foraminifera, and other microscopic 
organisms, at the end of the next chapter. The larger examples 
should be left attached to a piece of chalk, when practicable, 
and the surrounding stone removed with a knife or graver, 
so as to expose as much of the fossil as may be required for 
the display of its characters, without loosening its attach- 
ment to the block. When the investing chalk is very hard, 
frequently pencilling the specimen with vinegar, or dilute 
hydrochloric acid, will soften the stone, and render its re- 
moval easy, by means of a soft brush: when acid is em- 
ployed, the specimen must afterwards be well rinsed in cold 
water.t 
The zoophytes that are in part flint, and part chalk, as 
the Ventriculites, (ante, p. 244, Lign. 81,) can rarely be ob- 
tained, except through the quarrymen who have been in- 
structed how to extract them from the rock. The first 
* Mr. Deane’s splendid and masterly work on Corals, should be 
studied by those who wish to be acquainted with the present state of 
this branch of natural history. 
+ It may be well to caution the collector against employing sul- 
phuric acid (commonly called ol of vitriol) for this purpose, for a 
white insoluble deposit (sulphate of lime) will thus be formed on the 
specimen, and its appearance irremediably injured. Many of the 
fossil corals obtained from the chalk of Dover Cliffs, are so saturated 
with muriate of soda, from long exposure to the spray of the sea, as 
to be liable to decomposition in the course of a few weeks, and are 
therefore not worth purchasing of the dealers. 
cy 
