One explanation can be given; and it is that of the strong dissolving power of sea-water. After a depth of about two miles, the delicate little shells fail to resist that power. Once at the bottom, they might be covered up and preserved; but they cease to exist _en route_ thither. So in this as in many other instances, we see opposite forces at work. The one force is perpetually undoing what the other force is perpetually doing. Innumerable multitudes of living creatures are at work, taking lime from the water, and constructing carbonate-of-lime. But the ocean is ever seeking to re-dissolve that carbonate-of-lime. Another difficult question as to the ooze was--whether the shells of which it is mainly made were those of Foraminifera living in the deep sea, far down below the surface, or of Foraminifera living near the surface. Able men took both sides of the discussion, some ascribing the ooze entirely to deep-sea jelly-specks, others ascribing it entirely to surface jelly-specks. The question cannot be said yet to have met with complete settlement. But here once more it seems that both sides have been partly in the right. There are Foraminifera which live only at great depths, and there are Foraminifera which live only near the surface. The ooze is found to consist of shells belonging to both kinds, though it may be that the surface species carry away the palm in point of greater multitudes. CHAPTER XV. OF OCEAN-WEEDS “Have hung My dank and dripping weeds.”--Trans. HORACE. “The tide is full, the moon lies fair Upon the Straits; on the French Coast the light Gleams, and is gone; the Cliffs of England stand, Glimmering and vast, out in the tranquil bay.” MATTHEW ARNOLD. Scattered through the vast Chalk-beds of Great Britain and the Continent are thousands of layers of FLINT, such layers as any of us may have seen intersecting the smooth white face of Chalk Cliffs. And as with Chalk, so with Flint--we at once find ourselves upon the track of Life. Not indeed always of animal life. Sometimes vegetable life takes its place. Though the highest Vegetables stand on a lower level than the lowest Animals, they too have Life, and thereby they are entirely apart from the whole world of inanimate Nature. Widely distinct are the Animal Kingdom and the Vegetable Kingdom; yet on the borderland between the two is found a hazy belt of uncertainty. So gently does the one glide into the other that, though a line of demarcation does exist, it is not always easily made out. But the transition from the lowest form of that which _lives_ to any and every form of that which has no Life is abrupt, absolute, precipitous. Here we see no quiet sliding of the one into the other, no wavering hesitancy as to whether a certain something may belong to this or that side of the dividing parapet.