Aeolipile. A name that has been given to an instrument variously modified, for converting in a close vessel water into steam. The first individual who used it, appears to have been Hero the elder, a Grecian mechanic, who settled in Alexandria about 130 years prior to the Christian era, whose ingenuity and talents being fostered by the Egyptian monarch, was the probable cause of his interesting discoveries being handed down to us in his work entitled Spiri-talia, or Pneumatica. Although in the state that he has presented it to us in his aeolipile, it cannot be regarded as one of his most useful inventions, (his fountain for raising water by compressed air possessing far more intrinsic merit,) still as being the earliest germ of that great mechanic power which seems destined to change the face of the entire civilized world, it is well deserving of a description in this place, which we shall give with reference to the subjoined figure. Over a small furnace was placed a vase or caldron a, containing water, from the cover of which proceeded two arms b c, forming the axis of a hollow globe d. The arm b is a steam pipe, the other arm c is solid, having its extremity formed into a conical pivot.

At right angles to the axis of the hollow globe, there proceed from it two tubes ee, bent at their extremities, which form the outlets of the steam. Heat being applied to the caldron, raises the steam, which flowing through the tubular axis b, enters the globe; thence the steam finds its way through the tubes e e into the atmosphere, the reaction of the latter producing a rotatory motion of the globe, the velocity of which will depend upon the strength of the steam.