Now there is something very remarkable about Carbonate of Lime. It is absolutely different from the materials of which sandstone and granite are made. Wherever we stumble upon carbonate-of-lime, there we are on the track of LIFE. And the moment that we touch upon LIFE, even in its simplest and lowest forms, we rise to a higher level. Hitherto, in this subject of the Mighty Deep, we have had to do with things inanimate; things without consciousness; things blindly controlled by the forces of nature. In the story of ocean-waters, of ocean-salt, of ocean-rivers, of icebergs and ice-floes, Life has no part. There is no life in a grain of sand, no life in a granite rock. But here, suddenly, we are arrested. Here, in the composition of Chalk, we come across a difference. Here, at one step, we pass over a vast dividing chasm, and stand face to face with that which has Life. Not indeed that which lives now, but with that which did live, the signs of which may better help us to understand Life in the present. Is this so new? Have we not already in former chapters found tokens of creatures which once existed, of fossil remains embedded in rock? Yes; but that was not the same. Fossil remains are discovered in many kinds of stratified rock. Here we are not concerned with separate remains, buried in masses of chalk, but with the actual substance of chalk itself. The mere building of it, as earlier told, closely resembles the building of sandstone. Chalk, like sandstone, was formed in past ages out of tiny particles, carried by ocean-waves, dropped upon ocean’s bed, slowly consolidated, then gradually upheaved. Particles of---- Ah, there we reach the great distinction! Not particles of inanimate mineral substances, such as grains of quartz. No; but particles which once formed the habitation of living creatures. More than this--particles which once shared in the Life of the beings with which for the time they were in touch. Infinitesimal specks, often so minute as to appear only as fine dust to man’s unaided sight; yet real organic remains, each one of which has been the home of an active animal. A lump of chalk is a mass of densely packed tiny fossil shells, more or less crushed and broken. It has been reckoned that a cubic inch of chalk probably holds at least one million shells. Try to imagine what this means. The work of the Ocean in building solid sandstone, from unnumbered myriads of myriads of grains of sand, is marvellous enough. But here we have something far more wonderful. Here we have rocks and cliffs, ranges of hills and extents of country, to a great degree composed of almost invisible sea-shells, so small, so numerous, that a million or more of them may be packed into one little cubic inch of space, while the chalk-beds lie through hundreds of miles.