The Coral Island: A Tale of the Pacific Ocean

by R. M. Ballantyne

I repeated my thoughts to Jack, who, I was happy to find, quite agreed with me. “Your best plan,” he said, “will be to put very few animals at first into your tank, and add more as you find it will bear them. And look here,” he added, pointing to the sides of the tank, which, for the space of two inches above the water-level, were incrusted with salt, “you must carry your philosophy a little farther, Ralph. That water has evaporated so much that it is too salt for anything to live in. You will require to add fresh water now and then, in order to keep it at the same degree of saltness as the sea.”

“Very true, Jack, that never struck me before,” said I.

“And, now I think of it,” continued Jack, “it seems to me that the surest way of arranging your tank so as to get it to keep pure and in good condition, will be to imitate the ocean in it. In fact make it a miniature Pacific. I don’t see how you can hope to succeed unless you do that.”

“Most true,” said I, pondering what my companion said. “But I fear that that will be very difficult.”

“Not at all,” cried Jack, rolling his towel up into a ball, and throwing it into the face of Peterkin, who had been grinning and winking at him during the last five minutes. “Not at all. Look here. There is water of a certain saltness in the sea; well, fill your tank with sea water, and keep it at that saltness by marking the height at which the water stands on the sides. When it evaporates a little, pour in fresh water from the brook till it comes up to the mark, and then it will be right, for the salt does not evaporate with the water. Then, there’s lots of sea-weed in the sea;—well, go and get one or two bits of sea-weed, and put them into your tank. Of course the weed must be alive, and growing to little stones; or you can chip a bit off the rocks with the weed sticking to it. Then, if you like, you can throw a little sand and gravel into your tank, and the thing’s complete.”

“Nay, not quite,” said Peterkin, who had been gravely attentive to this off-hand advice, “not quite; you must first make three little men to dive in it before it can be said to be perfect, and that would be rather difficult, I fear, for two of them would require to be philosophers. But hallo! what’s this? I say, Ralph, look here. There’s one o’ your crabs up to something uncommon. It’s performing the most remarkable operation for a crab I ever saw,—taking off its coat, I do believe, before going to bed!”

We hastily stooped over the tank, and certainly were not a little amused at the conduct of one of the crabs which still survived it companions. It was one of the common small crabs, like to those that are found running about everywhere on the coasts of England. While we gazed at it, we observed its back to split away from the lower part of its body, and out of the gap thus formed came a soft lump which moved and writhed unceasingly. This lump continued to increase in size until it appeared like a bunch of crab’s legs: and, indeed, such it proved in a very few minutes to be; for the points of the toes were at length extricated from this hole in its back, the legs spread out, the body followed, and the crab walked away quite entire, even to the points of its nipper-claws, leaving a perfectly entire shell behind it, so that, when we looked, it seemed as though there were two complete crabs instead of one!

“Well!” exclaimed Peterkin, drawing a long breath, “I’ve heard of a man jumping out of his skin and sitting down in his skeleton in order to cool himself, but I never expected to see a crab do it!”

We were, in truth, much amazed at this spectacle, and the more so when we observed that the new crab was larger than the crab that it came out of. It was also quite soft, but by next morning its skin had hardened into a good shell. We came thus to know that crabs grow in this way, and not by the growing of their shells, as we had always thought before we saw this wonderful operation.

Now I considered well the advice which Jack had given me about preparing my tank, and the more I thought of it, the more I came to regard it as very sound and worthy of being acted on. So I forthwith put his plan in execution, and found it to answer excellently well, indeed much beyond my expectation; for I found that after a little experience had taught me the proper proportion of sea-weed and animals to put into a certain amount of water, the tank needed no farther attendance; and, moreover, I did not require ever afterwards to renew or change the sea-water, but only to add a very little fresh water from the brook, now and then, as the other evaporated. I therefore concluded that if I had been suddenly conveyed, along with my tank, into some region where there was no salt sea at all, my little sea and my sea-fish would have continued to thrive and to prosper notwithstanding. This made me greatly to desire that those people in the world who live far inland might know of my wonderful tank, and, by having materials like to those of which it was made conveyed to them, thus be enabled to watch the habits of those most mysterious animals that reside in the sea, and examine with their own eyes the wonders of the great deep.