from which a pipe communicates with a third cylinder, in which the piston works, and into which the air is admitted alternately under and over the piston, while the vacuum extends to its opposite sides. By this contrivance a much greater rapidity of motion may be given to the piston, it required.

The ways being therefore explained, in which, by the pressure of the air, the vacuum produced (and continued) is applied to useful purposes, Mr. Brown claims to be the inventor of the combination above described for effecting a vacuum, however much it may be varied by the mechanical means with which it may be used, and also the inventor of applying a vacuum produced by the combustion of inflammable gas, to raising water, and to the production of motion in machinery by the pressure of the atmosphere.

The different scientific journals were much divided, as to the result of Mr. Brown's experiments: not that any one questioned the effective operation of an engine on this principle, such having been clearly established by actual construction, soon after the publication of the scheme; the question simply being, whether the apparatus could be purchased and maintained, at a less or at a greater cost, than the steam on the most approved construction. It would be needless to repeat the various inquiries on this subject, nearly all of them having been merely theoretical, and some of them written by persons unable to calculate from all the facts of the case. We have before us the report of a committee, appointed by the shareholders of a company called the "Canal Gas Engine Company," formed expressly for the purpose of trying on a large scale, and if practicable, of bringing into general use, Mr. Brown's engine. Mr. Routh, a director, stated, that "They had been appointed to ascertain the practicability of Mr. Brown's engine, for the application of gas instead of steam, to the propulsion of vessels either on canals or navigable rivers. Two experiments had been made; the one on the 1st of January, and the other on the previous day, under the inspection of the committee. The gentlemen who were entrusted to examine and report to the shareholders, dif

fered greatly in their opinions derived from those experiments; but they were now ready to state their individual opinions on the subject, which was certainly one of great national importance. The day on which the first experi ment was made, being extremely boisterous, was particularly unfavourable to the performance of the experiment, inasmuch as the boat itself was leaky, and the machinery defective. The boat then made way, but not in such a manner, as to give a highly advantageous opinion of the powers of the engine. In the second experiment, however, it was in a more perfect state. The boat, which was started from Blackfriars Bridge, went at the rate of from seven to eight miles per hour, with all the regularity of steam boats; the paddles moved as regularly; and it appeared the power of the engine might be sustained for any length of time by gas, as well as by steam. It was the opinion of most persons present, that the engine answered every pur pose expected of it; and he owned that, as far as power went, it was his own opinion; but he considered that the expense of procuring gas would entirely prevent its application as a prime mover, instead of steam.-It was said that gas could be readily and cheaply procured by the decomposition of water. We understood the chairman to express himself of opinion, that this proposition had not been yet made out. He was decidedly of opinion that the company ought to be dissolved. In fact, it was impossibie that it could go on. The sum of rather more than £5000 had been subscribed. £1000 had been given to Mr. Brown, for the share of his patent right in the invention; £1000 more had been paid for constructing an engine, under his superintendance, for the application of his principle, which had failed. £1700 was locked up in the hands of their bankers, Sir John Perring and Co.; then £300 was paid for a boat, and the remaining available funds were otherwise absorbed. The company could not, therefore, proceed without another call, which could not of course be made, or, if made, attended to."

On the other hand, it was stated by Mr. Brown, "that the experiment had succeeded to the full extent contem

plated by himself and friends. On the first time of the experiment, the engine itself was not got into any state of completeness, until the midnight preceding the morning of trial, and the boat was accidentally run on shore, and stove in her side. They had to make the experiment on a boisterous day, and before this accident was repaired, the paddle-wheel was found to be too small, and deficient in power. A second experiment was made on the river, before the Lords of the Admiralty and a number of scientific men, and the result was such as to confirm their minds in favour of its eligibility. He would state further, that it would, without doubt, be adopted."* He did not, however, shew by figures, or any other calculation, that gas could be obtained at such a cost, as to allow a fair competition with the steam engine; and we are therefore inclined to give full credit to the statements of the chairman and directors, namely, "that the expense of procuring gas would entirely supersede its application as a prime mover, instead of steam."

Previously to the year 1823, carbonic acid had never been exhibited but in the gaseous or aeriform state, and it was a commonly received opinion, that no degree of pressure nor of cold would cause it to assume a more concentrated form; in the early part of that year, however, Mr. Faraday of the Royal Society, under the direction of its then illustrious president, Sir H. Davy, succeeded in reducing it (as well as several other gases) into a liquid state, by the mechanical pressure of a condensing pump.

This liquid, at the temperature of freezing water, in its endeavour to assume the aeriform state, exerts an expansive force equal to 30 atmospheres ; at ordinary temperatures, a force of from 40 to 50 atmospheres ; and on a heat of only 120 Fah. being applied, the force is increased to 90 atmospheres; the pressure increasing in a similar ratio for higher degrees of heat; in other words, at the rate of about 11 or 12 pounds increased pressure upon the inch, for every single additional degree of heat.

• Public Ledger.

We may easily conceive that to construct an apparatus by which a power so immense, and apparently so economical, might be rendered available, like the steam engine, as a first mover to all kinds of machinery, has occupied the attention and study of many of the most scientific and clever men, not only of this, but of every country in the civilised world; since it cannot be doubted that the paper of Sir H. Davy, "on the application of liquids formed by the condensation of gases as mechanical agents," has been published every where, and translated into the language of every country where mechanics are studied as a science. Nearly four years have intervened since the publication of the important facts detailed in the paper alluded to, during which period, not only individual talent, but the abilities of one of our first chemists have been united with those of one of our most eminent engineers, for the accomplishment of this great desideratum. In this honourable spirit of rivalry, the talents of Mr. M. I. Brunel have been employed, and he has so far satisfied himself of the advantages arising from such an apparatus, as to have procured a patent for an engine on this principle.

It is proper that we should here remark, that the patent right for Mr. Brunel's apparatus is not limited to the employment of carbonic acid, but that it extends to all liquids which are the result of the condensation of the gases. The preference being however given to the former, we may perhaps infer that the engine we have to describe, is better adapted to the peculiar properties of carbonic acid gas, than to those of the others. Carbonic acid gas may be obtained by decomposing any of the carbonates by the action of the common acids. The mode of obtaining the liquid from the gas, is by forming the gas under a gasometer, and condensing it afterwards in another vessel, by means of a condensing pump, and continuing the operation until it passes to the liquid state.

The apparatus, as shewn at fig. 2, consists of five distinct cylindrical vessels; the two exterior vessels a and b contain the carbonic acid reduced to the liquid form, and are called the receivers; from these it passes into the two 2 M

12.