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with Marion de l'Orme, in February, 1641. The apocryphal legend also figures conspicuously, (without any reference being made to the work of Miss Costello), in Mr. Smiles'

Life of George Stephenson, Railway Engineer :'_“Solomon “ de Caus,” says Mr. Smiles, “ who was shut up for his “ supposed madness in the Bicêtre at Paris, seems to have “ been the first to conceive the idea of employing steam for “ moving carriages on land as well as ships at sea. Marion " de l'Orme, in a letter to the Marquis de Cinq-Mars, dated “ Paris, February, 1641,” &c.; and then follows the greater portion of Miss de l'Orme's billet-doux. “It appears,” adds Mr. Smiles, “ that the Marquis of Worcester was greatly “ struck by the appearance of De Caus, and afterwards studied “his book, portions of which he embodied in his “Century « • of Inventions.'” This must be all very entertaining to the contriver of the hoax which has met with such easy victims; but we hope that henceforth the letter in question may no longer be looked upon with so much greater respect than it deserves, as a source of historic truth.

It is gratifying to be enabled to add that the fictitious letter, although at first attended with success, and adopted, in various countries, as the groundwork of dramatic performances, has been rejected with just indignation by several French writers of credit; among others, by the author of an interesting article on Solomon De Caus, in the Magasin • Pittoresque' for 1850; by M. Figuier, in his able work on the history of some modern scientific discoveries; and also, we understand, by the Society of Antiquaries of Normandy.*

The few years before and after the middle of the seventeenth century form a most brilliant era in the history of discoveries in natural philosophy; and, quite independent of the hydraulic machine invented by the Marquis of Worcester, some great advances were made at that time, by philosophers whose names have not usually been associated with the steamengine, towards the right explanation of principles on which its action was at first to depend, as well as towards the construction of the apparatus.

* For these last references we have have fallen into another when they to thank the goodness of T. Watts, say that De Caus was in the service of Esq., of the British Museum, a gentle- " Frederick V., Duke of Bavaria ;" man whose extensive learning is only thus confounding Frederick the Elecequalled by the courtesy with which tor Palatine with his great enemy he makes it available to others. It is Maximilian, Duke of Bavaria, who by singular enough that, in correcting force of arms deprived the Elector one historical error, both M. Figuier both of his dominions and of his and the Magasin Pittoresque' should dignity.

Galileo, in 1640-41, surmised the true nature of a vacuum, and of the pressure of the atmosphere. His pupil Torricelli, pursuing the subject after the death of Galileo, invented the barometer, and proved the theory in 1643. Pascal, hearing of it, as he says, at Rouen, published, in 1647, his · Nouvelles • Expériences touchant le Vuide,' confirming the deductions of the Italian philosophers; and he caused to be made, in 1648, the memorable experiment of the Puy de Dôme, thereby establishing the variation in the pressure of the atmosphere at different heights, which Descartes had before conjectured:“ Ce qui nous ravit tous,” says M. Perier, who, at Pascal's request, made the experiment,-in speaking of the phenomenon observed in it,—"d'admiration et d'étonnement.” He further developed the theory, in 1653, by many experiments, which were not published until 1663, a year subsequent to his death, in his · Traitez de l'Equilibre des Liqueurs et de • la Pesanteur de la Masse de l'Air.'

Otto de Guericke had in the meantime applied himself to the same subject, and invented an air-pump, the effects of which he exhibited to the assembled German Princes at the Diet of Ratisbon in 1654. An account of this was published by Gaspar Schottus, first in his book De Arte Mechanicâ • Hydraulicopneumaticâ,' in 1657, to which it forms an appendix; and afterwards, with several additions, as Guericke has informed us, in his Technica Curiosa,' Norimb. 1664, 4to. Robert Boyle passed some time at Florence in 1642, in which year Galileo died at a neighbouring village ; he published, in 1660, 'New Experiments upon the Spring of Air,' and described therein an air-pump he had invented two or three years before, and which had been improved by Hooke. The experiments of the “Accademia del Cimento,” which are

very full upon this subject, were published at Florence in 1666. Otto Guericke did not himself publish until a later period; for although he states in the preface to his work entitled 'Experimenta Nova Magdeburgica de Vacuo Spatio,' that it was completed on the 14th of March, 1663, yet he adds, that, partly in consequence of illness, and partly from other occupations, a delay of seven years occurred in placing it before the world. It was at last published at Amsterdam in 1672; and its appearance then seems to have been in part owing to the exertions of certain illustrious friends of its author. Looking at chapters 27 and 28 of book 11., and at the iconismi, or plates, numbered xiv. and xv., where Guericke describes and delineates a cylinder with a packed piston and rod, and states his mode of forming a vacuum, by extracting the air under the piston by means of his air-pump, and thus producing a power for raising weights by the pressure of the atmosphere, we observe a great similarity to the apparatus in which Papin, several years later, when residing at Marburg, formed his vacuum by the condensation of steam. Papin's first publication, also, which appeared in 1674, within two years of that of Guericke, was a description of new experiments on a vacuum, and of the machines, or air-pumps, employed to make them; and many of his subsequent papers in the ‘Philosophical Transactions' are on the same subject. Thus we think it quite evident that the Marburg Professor not only borrowed the form of the apparatus, but took the novel idea of using the pressure of the atmosphere as a power, from the far-famed burgomaster of Magdeburg; and Germany has a just claim to a share in the invention of THE GREAT MACHINE, as it is called in the letter to the Marchioness of Worcester from her confessor.

The notion of the existence of such a thing as a vacuum,which the old doctrine had taught that “Nature abhorred,”— and the right explanation of its true nature; the construction and use of the air-pump; the cylinder with its piston-rod, and piston packed so as to be air-tight although moveable in the cylinder, and with its upper surface exposed, so that the air should act on it as a power, when the close cylinder beneath

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was exhausted; are all so many distinct steps towards the formation of the atmospheric steam-engine of last century: which, under the hand of Watt, cast off altogether its dependence on the atmosphere, and for the first time became in every sense a true steam-engine; deriving its vacuum from the condensation of steam on one side of the piston, and its power from the impulse of steam on the other, and vice versâ, according as the stroke made is downwards, and upwards, in uninterrupted succession.

CHAPTER XI.

DENYS PAPIN - HIS MEMOIR OF 1690 – ATTEMPT TO FORM A VACUUM BY GUNPOWDER — HIS SUBSEQUENT ADOPTION OF SAVERY'S PRINCIPLE

HIS DIGESTER -MISTAKES OF ENGLISH AND OF FRENCH WRITERS IN REGARD TO HIS INVENTIONS TRANSLATION OF HIS PAPER OF 1690.

We come now to the Memoir in which Denys, or Dionysius Papin, in the year 1690, availing himself of the apparatus of Guericke, and of the true ideas as to a vacuum and the pressure of the atmosphere, of which we have just been speaking, set forth another important fact which he had observed. This was, that if a close cylinder were filled with steam, and the steam were then allowed to condense, a vacuum would be formed within the cylinder; and that, consequently, a moveable piston, fitted to the interior of the cylinder, would then fall, under the pressure of the atmosphere ; just as it did in Otto Guericke's experiment, where the vacuum had been formed by the air-pump.

Papin mentions, in the outset of his Memoir, that he had applied steam to that purpose, in consequence of the failure of a previous attempt he had made to obtain a vacuum by the explosion of gunpowder, in the same cylinder, beneath the piston; the explosion always leaving the vacuum imperfect, on account, as he supposed, of a portion of the air which remained, or, as we should now say, of the gases which were the products of the combustion. But he proposed to carry out his ingenious idea of forming the vacuum by condensation, by the clumsy, tedious, and unprofitable expedient of removing the fire from beneath the cylinder, previous to each stroke or descent of the piston; a method which even the greatest of his admirers among his own countrymen admits was “scarcely tolerable even in an experiment in“ tended to verify the accuracy of a principle;" and which

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