written by James Rollock, an old dependant of his Lordship, complete the volume.

If the Marquis ever made an experiment on the elasticity of steam, (for the bursting of the cannon is a truly questionable one,) or if he ever attempted to carry his project into execution by constructing an engine, all records of his experiment and apparatus are lost. The more probable opinion is, that he never made either the one or the other; and this surmise is almost strengthened into a certainty, from a clause in the Act of Parliament, granting him the privilege of monopoly; for it is there expressly stated, (and the statement is a proof that the proceeding was an unusual one,) that the patent was secured to the Marquis, " on his simple affirmation of his having made the discovery." It were almost superfluous to suggest the improbability of this statement having been made, if he could have referred to the evidence of an engine or of an experiment.

Tradition has preserved nothing on this subject, except an anecdote* of the Marquis's attention having been first drawn to the amazing force of steam, from observing the rising of the lid of a vessel which was employed in some culinary operation in his chamber, when he was confined in the Tower of London. We should, however, pay a sorry compliment to that "learning and industry" for which this nobleman is almost as much celebrated as for his ingenuity, were we to suppose him ignorant of Branca's book; or of De Caus's inventions, pub

* "A Treatise on Propelling Vessels by Steam, by Robertson Buchanan, Civil Engineer," Glasgow, 1816, p. 16.

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lished so near his time, in a country where he resided many years, and where the volume which contained them was a common book of reference to the philosopher and mechanic, even to a period long after that of the publication of the "Century of Inventions." And, lastly, we must suppose the Marquis acquainted with his contemporary Dr. Wilkins's project of the Oelipile.

It must, however, be acknowledged, that although his merit is at an immeasurable distance from that of the inventor, the Marquis of Worcester is entitled to some mention as the probable projector of an improvement in Steam Engine Apparatus. He may have imagined the advantages which would arise from adding another vessel to De Caus's contrivance, (shewn in the Fourth Figure,) in which the steam might be generated, and then admitted into a second vessel filled with cold water. But even this improvement (and it is an important one) can only be allowed to his Lordship after making an emendation, or correcting an error, in his account in the "Century of Inventions." Instead of reading "to force and refill with cold water," it would be necessary to say, "to force and empty of cold water."* Yet the manuscript

* Dr. Brewster has made the correction, although in other words. He reads, "One vessel of water being consumed, another begins to force, and then to fill itself with cold water." This is not only at variance with the spirit of the text, but with the process,-for the water is forced. The latter part of this unintelligible description, in the original, ought probably to be read as if the Marquis's apparatus consisted of two vessels similar to De Caus's, without a separate boiler. It would then be clear enough, and the Doctor's emendation would follow as a matter of course.

in the British Museum agrees, in the usual reading, with the printed copies.

From the opinion we have expressed of its being practically impossible to produce an apparatus fulfilling all the conditions of the description in the "Century of Inventions," without introducing parts which are unquestionably due to the inventive genius of other mechanics, it is with great diffidence we propose the apparatus represented in the Ninth Figure, as being nearer to the description than that shewn in the Eighth Figure, in so far as not using the pressure of the atmosphere, which, the Marquis states, is not a principle of his engine.

But, after all, it is impossible to decide from Lord Worcester's description whether two boilers are meant, and one receiving vessel;-or two vessels, and one boiler? Or only two vessels, like De Caus's, probably having each an eductionpipe and the proper cocks, to produce a continuity in the stream of water?-as in the Ninth Figure where the dotted lines rising from the vessel a, would then represent this pipe, the fire being made under each boiler alternately. And, when mention is made of one vessel of water rarefied by fire, driving up forty of cold water, should not this be understood as the proportion of water which would be converted into steam, in order to raise the remaining portion in the same vessel, forty feet high? An apparatus designed on this supposition, would satisfy the description nearer than

any.

Having so wide a choice, we will give the Mar

quis credit for an apparatus for generating the steam in a separate boiler. a, will therefore be that boiler; c, a pipe (having a stop-cock d,) connecting the boiler with the cold water vessel e, from which proceeds the eduction-pipe f; g, a pipe and funnel, to supply the boiler with water; h, a similar pipecock to supply the vessel e, with cold water, connected with a cistern, from which the water is to be raised; i, is a stop-cock on this pipe; k, a valve to prevent the return of the water which may be in the upper part of the pipe f.

When the steam in the boiler a, is allowed to enter the cold water vessel e, by turning the cock d, the water is raised in a jet through f, until the vessel e, is emptied. When this is the case, the cock d, is shut, and i, is opened, and the vessel e, is again filled with cold water. The cock i, is then shut, and the stop-cock d, is opened; and the steam from the boiler pressing on the surface of the water in e, forces it up the pipe f. When this is emptied the same operation is repeated, and so on successively. So that here the condition of the alternate opening and shutting two cocks is fulfilled; also the forcing and refilling of the vessels; and one vessel of water rarefied by fire would elevate double the quantity of that stated by the Marquis.

After the death of the late Doctor Robison of Edinburgh, there was a "List of Dr. Hooke's Inventions" found among the Professor's papers, which contained the following memorandum: "1678, proposed a Steam Engine on Newcomen's principle:"