no jerking nor straining of the working, but is smooth and uniform in its motion; and moreover as a first mover is not limited in its velocity to 220 nor to 2200 feet per minute; for it appears that Mr. Davenport's wheel makes from 600 to 1000 revolutions in a minute! There is no danger of explosions, and of destruction to the vessel and passengers, as in steam-engines. These peculiar mechanical properties together with the great saving of room and expense, cannot fail in establishing the use of Davenport's invention, and ultimately throwing the common steam-engine completely into the shade.

The person who does not know that engines may be made to act by other means than by steam produced from boiling water, surely cannot boast of being profoundly versed in mechanical science; there are certainly many things that "Nauticus" yet never dreamt of in his philosophy.

I had intended to have now written something concerning a remedy or substitute for the crank in steam-engines, but must defer this, till some other opportunity, and in the mean time subscribe myself, as I have been for fifteen years past,

Sir, your's very respectfully, THOMAS OXLEY. 3, Elizabeth-place, Westminster-road, April 26, 1838.

NOTES AND NOTICES.

Great Mongolfier Balloon.-An experimental trial of an immense machine was made on Tuesday, on the borders of Epping Forest, in the presence of the constructor and several scientific gentlemen connected with the undertaking, for the purpose of trying the effect of a newly-invented furnace by which the balloon is to be filled with heated air, instead of the imperfect open brazier used by Mongolfier, Pilâtre, Rozier, and others, in their ascents from Paris some years since. By means of this invention the possibility of any spark coming in contact with the machine during the inflation is entirely avoided, and although at one period of the experiment the temperature was raised to two hundred degrees, not the slightest appearance of danger was visible. So powerful were the means used to obtain the requisite degree of rarefaction,

that the vast machine was completely filled in eight minutes, and had then an ascending power of 1,200 lbs. exclusive of the furnace and car, the latter of which alone weighs, when adorned, 300 lbs., and is 15 feet long by 8 feet wide. Three persons ascended to a considerable height, but were restrained from making an aerial excursion, it being intended only to ascertain correctly the capabilities of the balloon. All the persons present expressed themselves extremely gratified with the perfect success of the experiment. The first ascent will take place from the Surrey Zoological Gardens, when the builder and two other gentlemen well versed in acrostation will ascend.-Essex Paper.

The Atlantic Steamers.-Much anxiety is evinced to learn the particulars of the voyage out of the Atlantic steamers, Sirius and Great Western, and especial interest is attached to the former, from the circumstance of her being furnished with Hall's condensers, which will thus undergo a decisive trial. The last news of her was on the 14th April, when she had been ten days out, and she was then gallantly steaming on at the rate (it is said) of two hundred and fifty miles a day. Both she and her opponent, it will be recollected, must have met on the outset of their passage with the strong westerly gales which prevailed in the beginning of April, and been much retarded in consequence. It is therefore tolerably certain that neither would arrive at New York within the "expected" time,-twelve days, although it may be anticipated that they will have beaten the sailing packets by a "pretty considerable way."

French Steamer in the Thames.-Hitherto all the steam-vessels frequenting the port of London have been virtually, if not ostensibly, of British ownership and origin. The French, however, have at length resolved to enter the field, and "carry the war into the enemy's quarters." A splendid new steamer, the "Phoenix," has been built at Havre for this purpose, and has just commenced running between her native port and London Bridge, between which places she intends to take up a regular station. She belongs to a French company, who are determined, if possible, to reap some of the benefits of the immense intercourse between the two capitals of England and France, by water as well as by land.

Sir John Soane's Benefactions.-The Scane Museum has just re-opened for the season, under the same regulations as last year,-regulations which operate to prevent any thing like the free admission of "the public." The "Soane Medal" is to be adjudged by the Institute of British Architects, and the subject for the present year is "the restoration of one of the ancient Baronial Castles of Great Britain." The first annual distribution of Sir John Soane's donations by will to distressed architects and architects' widows is also on the eve of taking place.

Charcoal Fuel.-In the London Magazine for December, 1758, there is the following paragraph in a division of the work called the "Monthly Chronologer," under the date Tuesday, Nov. 26:"Some persons having been almost suffocated lately by sleeping in a room wherein was a charcoal fire, it has been declared that experiment has proved, that charcoal fire wetted with salt dissolved in water will have no suffocating quality."

Complete Sets of the Mechanics' Magazine may now be had, twenty-seven volumes, half-cloth, price 11 78.

CHANTER AND CO.'S PATENT SMOKE

BURNER.

This invention essentially consists in so arranging the form of the furnace and position of the bars, that the fuel is regularly advanced by gravitation, without the aid of machinery, or any apparatus besides the simple instruments in common use for the management of furnaces. This is effected by placing the fire-bars at an angle of about 45°, and sloping the bottom of the boiler in the same degree; the carbon and various more inflammable gases are set free at the commencement of combustion at the upper end of the furnace, and being charged with the oxygen of the atmosphere proceed through and over the fire, which increases in heat to its lower end, gradually subjecting the less combustible gases to perfect combustion. Saving in fuel is thus effected; for in the present furnaces, these latter gases are not only passed off unconsumed, but by preventing the ignition of more combustible materials necessarily waste a large portion of the fuel. Thus the effect, in the operation of this furnance, may be stated to be that of obtaining, at the termination of the furnace, that intense degree of heat indispensable to the entire combustion of the various substances emitted from the burning fuel. The invention is exhibited in Mr. Chanter's specification in twelve different forms, shewing its application to various descriptions of furnaces. The engraving on our front page shews the application of the inclined fire-bars to a locomotive-engine furnace.

The

secondary furnaces beneath the principal fire-bars are for the purpose of heating the air as it enters the ash-pit; a hot blast is thereby obtained to effect the more complete combustion of the fuel. It appears from numerous testimonials, given by the first engineering authorities, that the intended object is effectually performed-the most common coal being burned without any appearance of smoke from the chimney.

STEAM NAVIGATION TO INDIA.

Sir, The pamphlet recently published by Sir John Ross for the purpose of showing the practicability of forming a steam communication with India via the Cape of Good Hope, has just come under my notice. I fully concur with him in opi

nion as to its practicability, but cannot yet bring myself to the belief that it can be accomplished in the short period he has stated (less than 50 days), for the following reasons:-First, assuming the distance to be about 12,000 miles by the most direct route; if the steam-vessels were able to maintain an average rate of 10 miles per hour, fifty days would be required for the voyage, exclusive of the necessary delays for receiving additional fuel on board, cleaning the machinery, &c. I have not at present met with any steam-vessel in the course of my somewhat extensive observation, that has been able to maintain such an average speed for several consecutive days, and my opportunities for acquiring information relative to the actual performance of steam-boats, are very frequent. Some few boats will maintain ten miles an hour for 30 or 40 hours, or even 80 hours ; yet these fast vessels would not be found to maintain an average of quite ten miles an hour during the whole of the voyages made from the 1st of January to the 30th June, or from the 1st July to the 31st December, in the British seas, with a fair average cargo on board; although these voyages are comparatively so short that the machinery may be reasonably expected to run the whole passage without requiring to be stopped for a sufficient length of time to occasion any material reduction in their average rate. Some months since I had an opportunity of examining the account (regularly kept) of the performance of some of the fastest boats plying between Glasgow and Liverpool, which fully bears me out in the preceding statement. The reports of the speed of steam-vessels are very generally exaggerated. An instance recently came to my knowledge in which it was confidently stated that a speed of 14 miles an hour had been attained by a new steamvessel. One of the gentlemen present at the trial proved that the speed attained was only from 114 to 11 miles per hour, and this with the engines in the best possible condition. His statement was confirmed by the facts, that the number of strokes and size of the wheels would not admit of her going at a greater speed unless the resistance of the boat is reduced in the same ratio as her velocity through the water is increased. Something like this theory was advanced by a gentleman upon whose work some remarks were

made by the present writer in a former number of your magazine.

It now appears highly probable that a communication by means of a line of steam-vessels with India, will be accomplished very shortly. Mr. Seaward, I am informed, has long since maintained its practicability; but not having had the opportunity of seeing his remarks upon the subject, I am unable to give you the details of his plan, which ought to be again brought under public notice.

The Dutch Government are taking measures for the introduction of steam navigation in the East Indies, and have some vessels building there for that purpose. Surely this ought to incite those who have the management of British interests in that quarter to take care that our pre-eminence there is not sacrificed through their supineness.

If we wish to carry steam navigation on to its greatest degree of perfection, there must be a cordial co-operation between the builders of the vessels and the constructors of the machinery, and the present jealous system of procedure be given up; for unless the vessel be properly constructed with regard to sailing properties, there will continue to be a vast expenditure of power to obtain speed beyond what is really required if the vessels be properly constructed for the purpose.

Another point requiring more attention than has hitherto been paid to it is, that the vessels should be constructed in such a manner as to have the necessary strength to bear the unavoidable strain arising from the unequal distribution of the weight of the machinery, in relation to the volume of water displaced. At some future period I may possibly offer some remarks upon the method by which the evils arising from this unequal distribution of weight may be avoided, without materially, if at all, increasing the expence beyond the present method of construction.

I am, Sir, your obedient servant,
GEORGE BAYLEY.

RAILWAY SIGNALS.

Sir, The attention of the scientific world has been so engrossed by railway projects as to leave but little time for the

consideration of those minor details which, however trifling they may appear at first, ultimately demand the careful attention of the engineer. Upon the perfection of the details, the ultimate success of the system depends. Already we have had painful evidence of the want of a judicious system of working day and night signals, announcing the approach to, or the departure from, stations or other parts of the line, where it appeared most requisite. There are two signals at present in use that require a passing notice. The first of these, the " whistle," certainly does possess considerable advantages; its portability, sharpness, and clearness of tone, renders it worthy of being retained in the service, and to be used on certain occasions. The other signal in use is of a far different kind; I know not what to call it. The war-whoop of the Blackfeet must be positive harmony compared with the execrable shriek caused by the rush of the steam! I should presume that a signal of this kind is likely to make matters worse-in case of an accident or alarm it would be perhaps difficult to tell which uttered the cry of danger, the engine or the passengers; add to this the alarm given to the female portion of the travellers, and there is sufficient ground for its abandonment. They manage these things better in Russia. I have lately seen an apparatus intended to be applied to the Russian locomotive engines which is well worth the attention of our railway directors. It consists of a moderate sized oblong box containing three or four "reed pipes" (as they would be technically termed by organ builders); these pipes are of brass, and shaped trumpet like. The box also contains a cylinder upon which the trumpet flourish or movement is pricked. The cylinder being put in motion by the action of the engine, the keys are raised, and act upon levers connected with the valves at the mouth end of the trumpets; the bellows attached to the apparatus (which is also worked by the same action) supply the wind to the instrument, and produce an excellent effect. A small swell might be added to increase or diminish the sound. I have had an opportunity of hearing one of these contrivances, and was much gratified with the accuracy of intonation. Near at hand the sounds were of immense volume, and I am certain fully equal to any thing re

quired on a railroad. The apparatus was constructed by Messrs. Robson and Son, organ builders, of St. Martin's lane.

It is a matter worth serious consideration whether the night signals could not be so contrived as to be clearly exhibited at a considerable distance (say one mile); a revolving light might be conveniently worked by the engine-or what might perhaps be better, a preparation of strontian, to be ignited at a given time in a receptacle hoisted for that purpose, but sufficiently protected from the weather. In perfecting the details of this estimable mode of travelling, much is required to be done let the correspondents of the Mechanics' Magazine render the public still further indebted to them by turning their attention to these matters, thereby ensuring greater safety to railway travelling.

Your's, &c.

CHRIS. DAVY. P.S. I regret to hear the unfounded rumours of the failure of the Kilsby Tunnel-nothing has occurred to warrant such statements. I shall shortly resume my description of that laborious work.-C. D.

CONDENSATION BY EXTERNAL COLD.

Sır,-Observing in your last number a claim to the invention for producing a vacuum by passing cold water between a series of metallic pipes or chambers open to the steam on its exit from the eduction pipe of the cylinder of a steam-engine set up for a Mr. Buchanan, in opposition to Mr. Hall, it may be right to state that several others appear to have a prior right of claim to either. Dr. Church, it would seem, obtained a patent in 1833, from which the latter inventions differ in no essential degree; and a gentleman connected with a large engine manufactory in Scotland, so early as the year 1828, had prepared the material, consisting of half-inch tubes, &c. for a condenser, arranged in the manner of Mr. Hall's; but owing to a pressure of business, it was not completed for some time after.

On reference to a memorandum, it appears that the gentleman above alluded to, informed the writer on the 2nd February, 1830, that "his mode of condensing by external cold fully succeeded;

DR. ARNOTT'S STOVE IMPROVED. Sir,-As the subject of warming apartments, &c. has occupied my attention for some time, I will, with your leave, make a few remarks thereon. First, as to Messrs. Harper and Joyce's stove. Everybody knew that a shovel-ful of live charcoal will burn in a brazier or other vessel, where there is a free circulation of air. H. and J.'s stove is no more in principle than the brazier in common use in the south of Europe, only of a different shape and with an apparatus at top, to regulate the exit of heated air and of carbonic acid gas. So much for this "nine days' wonder."

Next, as to Dr. Arnott's Stove and Essay. You are too severe in your critique (March 10). True there is much in his Essay we know already: the same remark applies to his "Elements of Physic;" but it is in the agreeable and familiar style in which the latter is written, that its chief merit consists. The Doctor certainly has been a principal agent in directing public attention to the subject. His stove can only be used for warming rooms, but I think he has made it too complicated for general use. I should dispense with the fire-screen, dome, funnel, and partition in the inside, as I conceive the last rather impedes than assists the free circulation of air in the stove. To prove this, put a small quantity of powdered gum myrrh in a wine glassful of water; apply heat to the side of the glass, or to the bottom partially, and an upward and downward current will soon be perceived; then introduce a piece of tin-plate so as to fit the sides of the glass, dividing it in two, but not reaching either to the top or bottom of the