Their halting-place was a pool, at whose head the advance of such salt tide as ran up was checked by a huge wall of volcanic rock, down which trickled the bright clear waters of one stream, while another took a clear plunge only a few yards away right into the pool. "What a place for a lunch!" said Sir John, as the occupants of the two boats now met on shore, and Mr Bartlett placed one of the two keepers from each boat in good places for observation of sea and land, so as to guard against surprise. Edward was now in his element, and while men went with buckets to get water from the springs by climbing up the side of the huge lava wall, he spread a cloth for the gentlemen's lunch and emptied a flat basket. The sailors soon selected their spot a dozen yards away, and their preparations were very simple. "Hold hard a minute," cried Edward to the men as they returned with the buckets filled. "I want one of those. Let's see which is the coldest. Here, Mr Jack, sir, just you come and try this," he cried the next minute, and on the boy approaching eager enough, the man plunged a glass into the first bucket and dipped it full of the most brilliantly clear water possible, and handed it very seriously to his young master. "Oh, this won't do, Ned," cried the boy; "it isn't cold--why it's hot." "Hot it is, sir, but just you taste it. I did." Jack took a pretty good sip and ejected it directly. "Ugh!" he cried with a wry face. "It's horrible; hot, salt, bitter, filthy, like rotten eggs; and yet it's as clear as crystal." "Yes, sir, it's about the worst swindle I ever had." "Here, father--Doctor Instow," cried the boy; and they came up and tried the water in turn, and looked at each other. "Regular volcanic water," said the doctor. "Why that would be a fortune in England; people would take it and bathe in it, and believe it would cure them of every ill under the sun, from a broken leg up to bilious fever. There's no doubt where that comes from. Look how full it is of gas." He pointed to a stream of tiny bubbles rising from the bottom of the glass. "Sea-water ain't it, sir?" said Edward respectfully; "but how did it get up there?" "Sea-water? no, my man. Beautifully clear, but strongly charged with sulphur, magnesia, soda, and iron. Which spring did it come from?" "That one which shoots out into the pool, sir," said one of the men. "And is the other the same?" cried Jack. "No, sir; cold as ice and quite fresh." Jack and the doctor climbed up to see the sources of the two springs, finding the hot not many yards from the edge of the rocky wall, where it was bubbling up from a little basin fringed with soft pinky-white stone, while the bottom of the pellucid source, which was too hot for the hand to be plunged in, was ornamented with beautiful crystals of the purest sulphur.