Some of the rivers flowing into Lake Valencia come from thermal springs, worthy of special note. These springs gush out at three points from the coastal granitic chain at Onoto, Mariara and Las Trincheras. I was only able to carefully examine the physical and geological relations of the thermal waters of Mariara and Las Trincheras. All the springs contain small amounts of sulphuretted hydrogen gas. The stink of rotten eggs, typical of this gas, could only be smelled very close to the spring. In one of the puddles, which had a temperature of 56.2°C, bubbles burst up at regular intervals of two to three minutes. I was not able to ignite the gas, not even the small amounts in the bubbles as they burst on the warm surface of the water, nor after collecting it in a bottle, despite feeling nausea caused more by the heat than by the gas. The water, when cold, is tasteless and quite drinkable.

The island of Lanzarote used to be called Titeroigotra. When theSpaniards arrived its inhabitants differed from those on the other islandsby their superior culture. They built their houses with cut stones whilethe Guanches of Tenerife lived in caves like troglodytes. At that time a strange custom - repeated only in Tibet- prevailed. A woman had several husbands, who each took it in turn to exercise the rights ofthe head of the family. Each husband was known as such during a lunarmonth; then another took his place while he returned to being a servant inthe house. In the fifteenth century the island of Lanzarote consisted of two states separated by a wall; a kindof monument, which outlives national enmities, found also in Scotland, Peruand China.