"Well, then," replied Mr. Elliot, "to-morrow we will apply ourselves to the needful instruction. I must, however, remind you that I do not approve of any animal's life being taken away in order to obtain its habitation. Empty shells are to be found, which will serve perfectly well for specimens; and should the colour not be so bright as you could wish, you will have the delightful consciousness that your amusements have been free from cruelty, and that you have not destroyed the life of any living, harmless creature, in the pursuit of pleasure. Indeed there is as much or more gratification in searching among the rocks, or digging into the sea-sand, with a view to watch the animal in its natural place, as in possessing its empty shell: and who knows what grand discoveries you may both make! "But I must leave you now--be ready for me after our usual dinner-hour." CHAPTER II. [Sidenote: INHABITANTS OF SHELLS.] "Conchology," said Mr. Elliot, on resuming the conversation with his children, "is that branch of natural history which comprehends the study of testaceous animals, or animals with _shell-coverings_, and includes those of the seas, the rivers, and the land. "All shells are formed of carbonate of lime. This you may easily prove by applying a little acid to a shell, and you will find that an effervescence takes place. "The animals that inhabit shells are bloodless, without bones, but provided with a heart, lungs, and mouth, together with other organs needful to their conformation. "Testaceous animals have the power of enlarging their habitations; they can also repair any injury that may occur to them. "Many kinds of shell-fish are made use of by man, and form a valuable article of food, such as oysters, cockles, muscles, scallops. The whelk is also used, and a species of murex. [Sidenote: FOSSIL SHELLS.] "A species of cowry is in use for money among some people of Africa; and pearls, so much valued as articles of ornament, are obtained from the oyster and mussel genera. "Within a few years, conchology has become a study of considerable importance, from its close connexion with geology. Students in the latter science must be well acquainted with fossil-shells, because they form so large a portion of organic remains. Species of recent shells, or those still existing, are also often found in a fossil state, while many fossil genera are now totally unknown in our earth and waters. "Thus you perceive that while you are obtaining knowledge in one science, you are preparing yourselves for making advances in another, most interesting and wonderful. You, Charles, who are likely to become a traveller, will perhaps in future years find the advantage of my present brief lessons. "I shall first endeavour to make you acquainted with the system of Linnæus; it is easily learned, and you should be familiar with it, as it is still adopted by some writers on conchology.