28 Beautiful Shells. 
acid with the water; but this must be done very 
cautiously, for if too strong it will remove all the 
lustre from the surface of the shell subjected to 
its influence. Sometimes the file, and a substance 
called pumice-stone, has to be used, but these are 
dangerous agents in inexperienced hands. The best 
polish for the shell, after the skin is removed, is a 
red earth called tripoli, applied on a piece of soft 
leather. 
FOSSIL SHELLS. 
An eminent geologist, named Dr. Mantell, has 
very beautifully and poetically termed rocks “the 
Medals of Creation.” As on coins and medals we 
see stamped enduring records of great historical 
events, so upon the rocks are written by the finger 
of God a history of some of the mighty changes 
which the earth has undergone, and fossil shells 
are among the plainest and most easily read of 
the characters or letters in which these truths are 
written. As Dr. Harvey, in his “ Sea-side Book,” 
observes, “ Shelly-coated mollusca have existed in 
the waters of the sea, and in rivers, from a very 
early period of the world’s history, and have left 
in its most stratified rocks and gravels abundance 
of their shells preserved in a more perfect manner 
