Bishop Wilkins writes, in 1648 ("Mathematical Magic"), of æolipiles as familiar and useful pieces of apparatus, and describes them as consisting "of some such material as may endure the fire, having a small hole at which they are filled with water, and out of which (when the vessels are heated) the air doth issue forth with a strong and lasting violence." "They are," the bishop adds, "frequently used for the exciting and contracting of heat in the melting of glasses or metals. They may also be contrived to be serviceable for sundry other pleasant uses, as for the moving of sails in a chimney-corner, the motion of which sails may be applied to the turning of a spit, or the like." Kircher gives an engraving ("Mundus Subterraneus") showing the last-named application of the æolipile; and Erckern ("Aula Subterranea," 1672) gives a picture illustrating their application to the production of a blast in smelting ores. They seem to have been frequently used, and in all parts of Europe, during the seventeenth century, for blowing fires in houses, as well as in the practical work of the various trades, and for improving the draft of chimneys. The latter application is revived very frequently by the modern inventor. SECTION II.--THE PERIOD OF APPLICATION--WORCESTER, PAPIN, AND SAVERY. We next meet with the first instance in which the expansive force of steam is supposed to have actually been applied to do important and useful work. In 1663, Edward Somerset, second Marquis of Worcester, published a curious collection of descriptions of his inventions, couched in obscure and singular language, and called "A Century of the Names and Scantlings of Inventions by me already Practised." One of these inventions is an apparatus for raising water by steam. The description was not accompanied by a drawing, but the sketch here given (Fig. 7) is thought probably to resemble one of his earlier contrivances very closely. Steam is generated in the boiler _a_, and thence is led into the vessel _e_, already nearly filled with water, and fitted up like the apparatus of De Caus. It drives the water in a jet out through the pipe _f_. The vessel _e_ is then shut off from the boiler _a_, is again filled through the pipe _h_, and the operation is repeated. Stuart thinks it possible that the marquis may have even made an engine with a piston, and sketches it.[15] The instruments of Porta and of De Caus were "steam fountains," and were probably applied, if used at all, merely to ornamental purposes. That of the Marquis of Worcester was actually used for the purpose of elevating water for practical purposes at Vauxhall, near London. [15] "Anecdotes of the Steam-Engine," vol. i., p. 61. [Illustration: Edward Somerset, the Second Marquis of Worcester.]