418
Book IV.
Three years after Bacon ’s death, the first printed account was publishedof any modern attempt (yet discovered) to communicate motion to solidsby steam, and as usual an eolipile was employed. Occupying a place onthe domestic hearth, as this Instrument did, the shrill current proceedingfrom it must have often excited attention, and led ingenious men to ex-tend the application of the blast to other purposes. The first idea thatwould occur to a novice when attempting to obtain a rotary movementfrom a current of vapor, would be that of a light wheel, having its wingsor vanes placed so as to receive the impulse, in a similar manner as littlepaper wheels are made to revolve, which children Support on a pin orwire and blow round with the mouth—or those which resemble Ventila-tors and revolve when held against the wind at the end of a stick. Thesetoys are vertical and horizontal windmills in miniature, and windmills andsmoke-jacks were the only Instruments in the 16th Century that revolvedby currents of air. Hence it was natural to imitate the movements ofthese in the first applications of steam; and the more so since steamat that time was generally considered to be nothing but air. a Such wasthe device of Giovanni Branca , as described in a work entitled The Ma-chine, written in Italian and Latin, and published at Rome in 1629. Thevolume contains sixty-three engravings. The twenty-fifth represents aneolipile, in the form of a negro’s head, and heated on a brazier: the blastproceeds from the mouth, and is directed against pallets or vanes on theperiphery of a large wheel, which he thus expected to turn round; andby means of a series of toothed wheels and pinions, to communicate mo-tion to stampers for pounding drugs. He proposed also to raise water byit with a chain of buckets, to saw timber, drive piles, &c.
It is hardly necessary to observe that the apparatus figured by Branca in all probability never existed except in his imagination, and that hisstampers, buckets, saws, piles, &c. could no more have been moved bythe blast of his eolipile, than those venerable trees were which Wilkinsand older writers have represented being torn up from the earth by a man’sbreath —the blast being directed against the vanes of a wheel, and theforce multiplied by a series of toothed wheels and pinions, until its energycould no longer be resisted by the roots. b Branca seems to have had thesechildish dreams in his mind when he proposed a continuous stream ofsteam from an eolipile, in lieu of intermitting puffs of air from a person’smouth. Italian writers have however claimed for him the invention ofthe steam-engine, a Claim quite as untenable as that put forth in behalf ofDecaus; for, in the first place, his mode of producing a rotary motion bya current of vapor was not new : all that can be accorded to him in thisrespect is, that he perhaps was the first to publish a figure and descriptionof it. Then it indicates neither ingenuity nor research. There probablynever was a boy that made and played with “ paper windmills” who wouldnot have at once suggested it, had he been consulted ; and when eolipileswere common, many a lad doubtless amused himself by making his “ mills”revolve in the current of vapor that issued from them. Moreover, thedevice is of no practical value. How infmitely does it fall short whencompared with that of Heron, (No. 180.) The philosophical principle of
a A horizontal and a vertical windmill are figured at folio 49 of Rivius’ translation ofVitruvius , A. D. 1548.
b By the multiplication of wheels and pinions it were easy to have made, says Wilkins,“ one of Sampson's hairs that was shaved off, to have been of more strength than all ofthem when they were on : by the help of these arts it is possible, as I shall demonstrate,for any man to lift up the greatest oak by the roots with a straw, to pull it up with « hair,or to blow it up with his breath.” Math. Magic, book i, chap. 14.