# The Coral Island/Chapter 12

Something wrong with the tank—Jack’s wisdom and Peterkin’s impertinence—Wonderful behaviour of a crab—Good wishes for those who dwell far from the sea—Jack commences to build a little boat.
Chapter XII.
SOMETHING WRONG WITH THE TANK—JACK'S WISDOM AND PETERKIN'S IMPERTINENCE—WONDERFUL BEHAVIOR OF A CRAB—GOOD WISHES FOR THOSE WHO DWELL FAR FROM THE SEA—JACK COMMENCES TO BUILD A LITTLE BOAT.
Rest is sweet as well for the body as for the mind. During my long experience, amid the Vicissitudes of a checkered life, I have found that periods of profound rest at certain intervals, in addition to the ordinary hours of repose, are necessary to the well-being of man. And the nature as well as the period of this rest varies, according to the different temperaments of individuals, and the peculiar circumstances in which they may chance to be placed. To those who work with their minds, bodily labor is rest. To those who labor with the body, deep sleep is rest. To the downcast, the weary, and the sorrowful, joy and peace are rest. Nay, further, I think that to the gay, the frivolous, the reckless, when sated with pleasures that cannot last, even sorrow proves to be rest of a kind, although, perchance, it were better that I should cal it relief than rest. There is, indeed, but one class of men to whom rest is denied. There is no rest to the wicked. At this I do but hint, however, as I treat not of that rest which is spiritual, but more particularly, of that which applies to the mind and to the body.
Of this rest we stood much in need on our return home, and we found it exceedingly sweet, when we indulged in ​it, after completing the journey just related. It had not, indeed, been a very long journey, nevertheless we had pursued it so diligently that our frames were not a little prostrated. Our minds were also very much exhausted in consequence of the many surprises, frequent alarms, and much profound thought, to which they had been subjected; so that when we lay down on the night of our return under the shelter of the bower, we fell immediately into very deep repose. I can state this with much certainty, for Jack afterwards admitted the fact, and Peterkin, although he stoutly denied it, I heard snoring loudly at least two minutes after lying down. In this condition we remained all night and the whole of the following day without awaking once, or so much as moving our positions. When we did awake it was near sunset, and we were all in such a state of lassitude that we merely rose to swallow a mouthful of food. As Peterkin remarked, in the midst of a yawn, we took breakfast at tea-time, and then went to bed again, where we lay till the following forenoon.
After this we arose very greatly refreshed, but much alarmed lest we had lost count of a day. I say we were much alarmed on this head, for we had carefully kept count of the days since we were cast upon our island, in order that we might remember the Sabbath-day, which day we had hitherto with one accord kept as a day of rest, and refrained from all work whatsoever. However, on considering the subject, we all three entertained the same opinion as to how long we had slept, and so our minds were put at ease.
We now hastened to our Water Garden to enjoy a bathe, and to see how did the animals which I had placed in the tank. We found the garden more charming, pellu​cid, and inviting than ever, and Jack and I plunged into its depth, and gambolled among its radiant coral groves; while Peterkin wallowed at the surface, and tried occasionally to kick us as we passed below. Having dressed, I then hastened to the tank; but what was my surprise and grief to find nearly all the animals dead, and the water in a putrid condition! I was greatly distressed at this, and wondered what could be the cause of it.
"Why, you precious humbug," said Peterkin, coming up to me, "how could you expect it to be otherwise? When fishes are accustomed to live in the Pacific Ocean, how can you expect them to exist in a hole like that?"
"Indeed, Peterkin," I replied, "there seems to be truth in what you say. Nevertheless, now I think of it, there must be some error in your reasoning; for, if I put in but a few very small animals, they will bear the same proportion to this pond that the millions of fish bear to the ocean."
"I say, Jack," cried Peterkin, waving his hand, "come here, like a good fellow. Ralph is actually talking philosophy. Do come to our assistance, for he's out o' sight beyond me already!"
"What's the matter?" inquired Jack, coming up, while he endeavored to scrub his long hair dry with a towel of cocoa-nut cloth.
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 its 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 further 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 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.
For many days after this, while Peterkin and Jack were busily employed in building a little boat out of the curious natural planks of the chesnut-tree, I spent much of my time in examining with the burning-glass the marvellous operations that were constantly going on in my tank. Here I saw those anemones which cling, like little red, yellow, and green blobs of jelly, to the rocks, put ​forth; as it were, a multitude of arms and wait till little fish or other small animalcules unwarily touched them, when they would instantly seize them, fold arm after arm around their victims, and so engulf them in their stomachs. Here I saw the ceaseless working of those little coral insects whose efforts have incrusted the islands of the Pacific with vast rocks, and surrounded them with enormous reefs. And I observed that many of these insects, though extremely minute, were very beautiful, coming out of their holes in a circle of fine threads, and having the form of a shuttlecock. Here I saw curious little barnacles opening a hole in their backs and constantly putting out a thin, feathery hand, with which, I doubt not, they dragged their food into their mouths. Here also, I saw those crabs which have shells only on the front of their bodies, but no shell whatever on their remarkably tender tails, so that, in order to find a protection to them, they thrust them into the empty shells of wilks, or some such fish, and when they grow too big for one, change into another. But most curious of all, I saw an animal which had the wonderful power, when it became ill, of casting its stomach and its teeth away from it, and getting an entirely new set in the course of a few months! All this I saw, and a great deal more, by means of my tank and my burning-glass, but I refrain from setting down more particulars here, as I have still much to tell of the adventures that befell us while we remained on this island.