Basin was covered by a lake, which possibly may have been a hot lake. In our American region, siliceous cones surmounting broad sloping mounds seem to predominate. Although New Zealand has a number of cones or chimneys, the large basins are more numerous. The pool of Te Tarata measures eighty by sixty feet, and the basin of Otakapuarangi is fifty feet in diameter. The springs in Iceland are comparatively small, as a rule, and chimney-like forms are not numerous.