At Gyser, not far from Skallholt, one of the Episcopal sees in Iceland, within the circumference of three English miles, forty or fifty boiling springs are seen together; and the largest, which is in the middle, particularly engaged our attention the whole of the day that we spent here. The aperture through which the water arose is nineteen feet in diameter; and round the top is a basin nine feet higher than the conduit. Here the water does not continually, but only by intervals several times a day; and, as I was informed by the Icelanders, in wet weather higher then at other times.
On the day we were there the water spouted ten different times, between the hours of six and eleven in the morning, each time the height of fifty or sixty feet. Before, the water had not risen above the margin of the pipe; but now it began by degrees to fill the upper basin, and at last to run over. Our guides told us that the water would soon spout up much higher than it had done.
Soon after four o'clock we observed that the earth began to tremble in three different places; as well as the top of a mountain which was about three hundred fathoms distant from the mouth of the spring. We also frequently heard a subterraneous noise, like the discharge of a cannon; and immediately afterwards a column of water spouted from the opening, which at a great height divided itself into several rays, and according to our observation was ninety-two feet high. Our great surprise at this uncommon force of the air and fire was increased, when many stones which we had flung into the aperture wore thrown up again with the spouting water." _Troil._
[94] Savary, Newcomen, Cawley, Watt, and Boulton, Englishmen; and Betancourt and the brothers Perrier, Frenchmen; are names well known in the history of steam-engines. And those persons who wish to acquaint themselves with the principles and manner of operation of this most important class of machines, says Dr. O. Gregory, may be referred to the following work:--The Repertory of Arts and Manufactures, the Philosophical Journal, and the Philosophical Magazine, in various places; the second volume of Mr. Brewster's edition of Ferguson's Select Lectures, the second volume of Gregory's Mechanics, and the second volume of Prony's treatise entitled Nouvelle Architecture Hydraulique.