[Illustration: Boiling Lakes of Roto Mahana] These waters are richly impregnated with carbonate of lime, which has formed all round the margins of the basins beautiful incrustations of snowy whiteness. The sand round the lake is very warm; and if a stick be thrust into it, jets of steam arise. Doubtless, some years hence, the enterprising English settlers will establish hot baths here. Not far from the lake there are smaller basins, in which the water is not beyond what would be agreeable for a warm bath; while it is of a blue colour and beautifully clear. On both banks of the river Waikato, also in this neighbourhood, are found numerous basins full of boiling mud or slime, which cannot be approached save with extreme care, owing to the softness and slipperiness of the soil. The largest of these basins is oval in form, 14 feet long by 8 feet wide, and about as much in depth. It contains hot mud of a bright red colour, being strongly impregnated with oxide of iron. Large viscous bubbles are continually rising to the top, and on bursting they emit a fetid, sulphureous smell. These phenomena are nearly akin to those of a mud volcano. CHAPTER XIII. Underground Sounds--Quito--Rio Apure--Guanaxuato--Melida--Nakous. Not the least remarkable among the phenomena produced by volcanic forces, are the strange underground noises which are occasionally heard. For the most part these are the preludes either of shocks of earthquake or of volcanic eruptions. Those which for months preceded the upheaval of the volcano of Jorullo, will recur to your remembrance. For about a month before the great mud eruption from Tunguragua on 4th February 1797, already described, there proceeded from the interior of that mountain noises of the most fearful kind. These would occur suddenly in the midst of perfect silence. They were heard by Antonio Pineda, the naturalist, who was there at the time, and they led him to foretell the approach of some great convulsion. Strange to say, however, the catastrophe itself was unaccompanied by underground noises any where near the volcano. But, stranger still, at Quito, which is distant about 200 miles, a short time after the eruption began, there were heard tremendous underground thunders. But this distance, between the site of the underground noises and the probable focus of disturbance, was far exceeded in another remarkable instance. It is stated by Humboldt that, in the grassy plains of Calaboso, on the banks of the Rio Apure, a tributary of the Orinoco, there were heard, over a large extent of country, loud underground thunders, unaccompanied by any shaking of the ground; while great streams of lava were being poured forth from the crater of Morne-Garou, in the Island of St. Vincent, at the distance of no less than 632 miles in a right line. This was as though an eruption of Mount Vesuvius were accompanied by underground thunders in Normandy.