Note 4 — HOME STUDIES IN CHEMISTRY AND PHYSICS.

“Minute animals.” The carbonate of lime which is found in rocks is most of it formed directly of shells, corals, and other animal remains. These little creatures take their stony-like structures from the water or from their food through the power of secretion, just as man forms his bones, and after their death they are given over to be made into rocks. The great extent and thickness of the limestone rocks of the earth give some idea of the amount of life that flourished there in past time.