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The pressure corresponding to the last notch to be equal to the bursting pressure, under which the engine is to work.The second valve to have a weight fixed immoveably upon it, the pres sure of which upon the seat, together with that of the atmosphere upon the valve, is equal to the working pressure of the engine. This valve should be so arranged as to admit not This end it should be placing additional enclosed. The rise allowed by the inclosure should father exceed half the radius of the valve-seat. vom iw 205/60190 St 9012

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Second. The Committee recommend to constructors the disk-valve. The diameter of the disk should not exceed once and a half that of the valve-seat, as a less ratio than this will leave sufficient margin, and any sensible tendency to close from the effect of the issuing current will certainly be avoided. That a cord be attached to the valech it may be raised at free valve. And that the working of ans of each t ascertained at least every two hours. 000096 & 97% CINO IN Fourth. That an open mercury-gauge be provided for each boiler of every engine not carrying more than twos atmospheres of working pressure. The height of the mercury to be indicated by a float which shall truly mark upon a graduated scale the bursting pressure in inches.

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For high-pressure boilers they recommend the thermometer, graduated to show the pres sures corresponding to the temperatures of saturated steam, as a convenient gauge.

Fifth. That the lever of the lock-up valve be bent upwards at the end, so that in rising it shall relieve the valve of part of the weight. A suitable proportion for such relief would be about one-tenth of the pressure derived from the weight, and the height of the bend above the lever should be regulated to meet this.

The lever would have a form similar to the annexed. The part ag, wh which is turned

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up, may be straight or otherwise. The adjustment should be made so that de is nearly nine-tenths of ac. g being the centre of gravity of the ball, lever, &c. will lie a little out of the centre of the weight, towards the fulcrum. aftats 209 sdr vd bare

Sixth. As there can be no doubt that the competition in regard to speed is, or has been, a strong temptation to an undue increase of pressure by engineers or firemen, it should be expressly prohibited by law, and

When the scale has been satisfactorily verified, it may be divided into one thou sand equal subordinate parts; and as the models of the adopted scale can he correctly multiplied, one may be preserved by each of the leading scientific societies of the European kingdoms. If two of the original pendulums could be preserved for ages, they might afford one simple method of ascertaining whether gravity and the earth's diurnal revolu tion did continue unchangeably the same. The conditions, as to the construction of the pendulums, and as to all other circumstances, are arbitrary and optional in the first instance; but when once pre scribed by scientific men, they must be rig rously adhered to afterwards to obtain the true result.

COLLIER'S STEAM-BOILER.

E.

Sir, I feel much obliged by your noticing my pamphlet, describing the particulars and experiments of my improved steam-boilers, in No. 695 of your valuable and widely-extended work, the Mechanics' Magazine, of the 3d inst.; and notwithstanding the severity of your remarks on my invention, I feel grateful to you for affording me an opportunity of explaining that part which you must admit I could not with delicacy have referred to in my pamphlet; and should not have done so now, had I not been

publicly attacked. You say, "The public will be surprised to learn (and we wonder Mr. Collier does not inform them how and why it so happened) that the Lords of the Admiralty ordered Mr. Collier's boilers to be removed, and the Meteor to be placed out of commission, till she could be refitted with boilers on the common plan."

Now, the facts as narrated in my pamphlet of the successful trials of my boilers till the arrival of the Meteor at Falmouth, after having successfully completed her voyage, are indisputable! It was not until after the boilers were removed, and altogether out of my control and superintendence, that an injury was done to them, and in consequence they were reported to their Lordships as unfit for use and past repair, without my being present or being referred to for explanation; this Report their Lordships ordered to be sent to me, and I accord

ingly inspected the boilers, when I found that a few of the chambers only were in a trifling degree injured; a defect that I could have repaired for a few pounds; I remonstrated with their Lordships on the subject, but without effect; they relied on their official reporter, for it was, I verily believe, pre-determined at Woolwich they should be condemned; and like many others who have had to do with Government reporters, 1 was obliged to submit, having no means to oppose them. I was, however, fortunately enabled to purchase the boilers; I say fortunately, because the possession of the boilers gives me now the means of convincing every unprejudiced individual how unmerited was the condemnation.

I am, sir, one of that body of me, chanics whose interests your valuable Magazine is presumed to uphold and protect; my existence depends on my ingenuity and talents, and I therefore claim equally with my fellow-labourers your unbiassed support and protection, if my inventions deserve it. I do not regret the observations you have made, as it enables me to invite and solicit as a favour, that all my brother mechanics and all men of science will inspect my boilers, and see the very trifling defect that caused the Government reporter to condemn my invention the labour of many anxious hours, and from which condemnation I have had for some time past to bear up. These identical boilers now stand at Globe-stairs Docks, having had the bottoms of the injured chambers repaired, and are now as sound and as good at this hour as the day they were first placed in the Meteor! Does not this speak for itself? I have added to these boilers such improvements as my experience suggested, and they are now in a condition to bid defiance to a recurrence of similar injury, either from accident or DESIGN. These improvements, you are pleased to say, are a little ingeniously arranged complication, and consequent increase of expense." Now, with great submission, 1 beg to state that I consider them judiciously arranged, and neither complicated nor increasing expense, for not one fraction will be added to the charge for my boilers. Toa discerning and discriminating public, I confidently appeal, and am sanguine enough to believe that it will ultimately awake to its interests, and duly appreciate

ON THE ACTION OF THE ATMOSPHERE.

Is not the agitation which takes place in water when it boils, caused by a current of air which enters through the hottom of the vessel, rises up through the water, and thereby causes the bubbling which is called boiling?

And does not the light coloured matter which is called steam consist of small particles, globules, or bubbles, thrown up and carried off from the surface by the air as it rushes through the body of warming or boiling water?

The process through which cold water passes to a boiling state, seems to indicate that the boiling or bubbling is caused by a current of air passing through it. The process commences by the formation of immense numbers of small bubbles on the bottom of the vessel, which gradually enlarge, run into each other, and begin to ascend to the surface of the water, and still they go on increasing in size and number, and in the rapidity of their risings, until they form here and there streams from the bottom of the pan to the surface of the water, and their united action produces the agitation in the water called boiling.

Now these appearances seem to be caused by air, and not by heat, for if a tin vessel containing water be partly impiersed in a vessel of boiling water, the water in the tin vessel may be raised to boiling heat, but it will not boil.

From this it seems that the heat is not the cause of the agitation in boiling

If a tumbler or common drinking glass be put into a pan of water sufficiently deep to cover or completely immerse the glass, and then turned upside down, that is, with the mouth to the bottom of the pan, the glass being turned under the water in such a manner that no air can enter it in the act of turning, and that the water may have full possession of the interior of the glass when turned, and the pan then put on the fire to boil, the air will gradually take possession of the glass and drive the water out. The operation of the air under the glass will be plainly perceived by watching the glass. W.

NOTES AND NOTICES.

Antiquity v. Novelty.-The New Islington Cattle Market seems destined to present another illustration of the difficulty with which an old-established trade is removed from its accustomed channels. When the public-spirited proprietor" had ob tined, in spite of the vigorous opposition offered by the City authorities, the Act duly authorising him to open his opposition-shop, it was expected that as soon as he commenced operations, the old Smithfield would be deserted, especially as the walls of the metropo is were profusely placarded with declarations purporting to be signed by all the principal graziers in the country, to the effect that they would employ no salesman who did not car y on business exclusively at Islington. Yet what has been the result? Ever since its opening in April, the return of "head of cattle" at Islington has presented a ludicrous contrast with that at Smithfield, and the number has been regularly diminishing even from its original insignificance. At length the degree of comparison seems to have reached the superlative. Monday, December 12th, was the butchers' carnival,-the grand day of preparation for Christmas,-and the following state ment shows the "state of the poll" at the rival markets:

may be supposed, by their triumph, the Common. Council are determined to proceed with vigour in the enlargement of old Smithfield. They have also had dear-honght experience of the danger of removal in matters of traffic!-the New Farringdon Market having proved so decided a failure, that it is seriously proposed forthwith to convert it into a prison!

Progress of a Delusion.-The South Australian Colonisation scheme is likely, at any rate, to have a fair trial; the Governor and a considerable number of emigrants being now on their way across the ocean, to test the wonder-working effects of a high price of land and low rate of wages on an infant colony. Before se'ting out they published the first number of a newspaper, of which the second is to appear in the capital of South Austra lia. The Governor is a Captain Hindmarsh, of the navy, who accepted the appointment after it had been thrown up by Colonel Napier (not the author of the "History of the Peninsular Wer", on the ground that it would be impossible to found the proposed colony without a military force of at least two hundred men. The Captain is to establish it with no other for e than the regulations as to the sale of land will give him. Time will show whether the soldier or the sailor is in the right, and, most probably, prove in all respects such a "telltale," as to astonish greatly the projectors of the scheme.

The Charter of the London University has just been made public It gives to the Fellows the power of conferring degrees, and King's College is considered a part of the University, the Gower-street Institution being for the future to be content with the title of the University Clege. The Earl of Burlington is the first Chancellor, and Mr. Lubbock, Vice Chancellor: the list of Fellows includes several distinguished names, with a preponderance, however, of those of the same way of thinking as the founders of the original establishment. The King reserves to himself the powers of Visitor; and the whole proceedings of the Senate appear to be liable to the control of the Secretary of State to such a degree, as to augur ill for the future independence of the new "seat of learning."

The Euphrates Expedition.-It is now under stood that Colonel Chesney's expedition is given up as impracticable, and that he is on his return to Europe, after expending a sum very far excee ing his e-timate before the Parliamentary Committee, without effecting the intended purpose.

City Improvements.-It has sometimes been recommended to carry on a bit-by-bit reform in our streets, instead of making those sweeping altera. tions which sweep so much money out of the City pocket. But from the account which Goethe gives, in the Memoirs of his Life," of the effect of an improvement of this kind which was in progress while he lived at Strasburg, in 1769, one would hardly feel inclined to recommend is adoption in any city which can possibly spare the wherewithal to repair and beautify at once. Blondel, an architect of Paris, had furnished the authorities of the town with a plan for amending its ways, by which 140 houses would gain increased space and 80 lose some they already had. The proprietors of these doomed houses were then prohibited from making any repairs to the exterior, and compelled when they rebuilt, which, of course, they were at last necessitated to do, to adopt the prescribed plan, thongh we do not hear of any compensation being made to those who suffered a loss by it. Of course, those who were entitled to bring their houses further forward were the most ready to rebuild, and accordingly the streets at that time presented a most chaotie appearance, from the number of newbuilt houses which were seen here and there rushing out "single-handed" into the middle of the street-while in other parts one might occasionally

be detected shrunk back in apparently the most behind unaccountable manner its neighbours. Goethe was not aware at the time he wrote, about forty years after, if the plan yet approached completion; but while he lived there, the strange appearance of the streets was the never-ending subject for the jokes and jeers of the students of Strasburg.

Algerine Mortar.-The mortar used by the an cients in their buildings has always been highly praised as much superior to that of the moderns. Pananti, a recent Italian writer on Algiers, paid a good deal of attention to the subject when residing in Africa, supp sing it probable, from the well. known stationary character of Oriental habits, that the ancient method of preparing it might be preserved there, though lost in Europe. He informs us, that the mortar used at Algiers is made of two parts wood-ashes, three parts lime, and one part sand-to this composi ion, they give the name Tabbi. After mixing these ingredients together, they throw in a quantity of oil, and heat the whole together for three days and nights without intermission, by which time it has attained the proper consistence. After being used in building, it be comes harder than marble, is impermeable to water, and resists the operation of Time and the elements.

Completion of the Great Viaduct on the Grand Junction Railway.-On Friday, Dec. 9, the ceremony of keying the last arch of this great structure took place. A party of the Directors from Liverpool attended for the purpose of witnessing the completion of this work, and were met by Mr. Locke, the engineer, and the resident engineers and contractors on the line. At two o'clock the trowel was presented to Mr. Heyworth, as the senior Director present, who, after placing the last stone in its bed, addressed the party present. Excellent speeches were afterwards delivered by Mr. Locke, the engineer, and the Rev. W. Stanhope, who spoke highly of the general good conduct of the workmen and all employed. In the evening the viaduct was illuminated with torches, and fireworks were displayed in great abundance, during which time the workmen were regaled with a good dinner and excellent cheer.-Staffordshire Advertiser.

The Supplement to Vol. XXV., containing Titie, Table of Contents, Index, and Plate of Specimens of English Metallic Engraving by Mr. Bate, was published on the 1st of December, price 64.

British and Foreign Patents taken out with economy and despatch; Specifications, Dis. claimers, and Amendments, prepared or revised; Caveats entered; and generally every Branch of Patent Business promptly transacted.

A complete list of Patents from the earliest period (15 Car. II. 1675.) to the present time may be examined. Fee 2s. 6d.; Clients, gratis. Patent Agency Office,

Peterborough court, Fleet-street.

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