Sir, I beg to submit to your readers, directions for making, managing, &c. the best of all possible boilers for steamengines in general, and marine engines in particular.

1. Let your chief I care be to make the boilers very complicated, and of such form and strength that the most trifling

accident shall eventually cause them to explode.

2. Connect them all to one steam-pipe; and take care that the openings into it are so formed that it is almost impossible for the steam to pass through; and then, to make the steam obedient to your will, put in immense fires, and thereby gene

rate steam very fast, and, by that means, oblige it to pass through the aforesaid awkward openings, somehow or other.

3. Be sure to form the flue so that a great part of the heat is appropriated to scorching the hull of the vessel, instead of to boiling the water; it may, perhaps, set the vessel on fire, which will cause an amusing excitement among the passengers, and relieve the dull monotony of the voyage.

4. Do not by any means neglect to place the chimney in such a situation as will give the engine-men a lively idea of the heat of the abode of a certain old gentleman, whose name is commonly abreviated to the first syllable.

Having made all these admirable arrangements, you may expect an explosion every hour. After it has occurred,

5. Employ some clever engineer to examine the boilers; and make a great parade of your own anxiety for a full and fair inquiry; if the engineer says the boilers are every thing they ought to be, all well; if he does not say so, bring forward as many persons as you can, who may safely swear they do not know why the boilers are not every thing they ought to be, and that, therefore, they consider they are;-declare you know they areand mystify the jury until they return a verdict which amounts to saying they have tried to understand the matter, and have failed in the attempt.

You may, however, think it prudent to make a few alterations, which you can easily do by sticking a few steam chests on the tops of the boilers, which will enable you to assure the people that, although they were perfectly safe before, they are a vast deal safer now; and that you are decidedly certain no accident can possibly happen. You may say all this with a safe conscience, because you will take care to be profoundly ignorant of every thing which would render your opinion worth one straw.

But you will prudently provide for contingencies that is, as you will not know whether the boilers are any safer or not, you will prepare yourself, as well as may be, to encounter another explosion; for which purpose the following hints may be useful :

Impress upon the mind of some one on board that, as soon after the explosion as possible, he is to go and look at the feed-cocks, and call some one else to look

too; if they can see that all the cocks are shut, and the boilers red-hot all over, it will be glorious; if not, the more red they can see the better.

Be prepared to state, that the men who have been killed, were very carefully chosen-that they were the most sober, experienced, and efficient engineers that could possibly be selected-that they were never guilty of inattention until they were employed on board your vessel; but that, when that was the case, they formed a perverse determination to do what they had manifestly no motive for doing, and which they must have known would end in their own destruction. You can intimate a suspicion, that they had agreed among themselves to commit suicide; or that they were quarrelling, and that some of them exploded the boiler for the purpose of giving the others a more effective "blowing up"; or any thing else that may occur to you, and which you think may do your cause some service, however monstrously inconsistent it may happen to be; for you must not think of sticking at trifles.

Possibly, about this time, the coroner will be kind enough to tell the jury, that he thinks they know as much of the matter as they ever will know, and the jury may think so too, and return much such a verdict as the first jury did-in which case you can try again, and kill a few

more.

But if the case happens to be before a jury who are most inconveniently determined to arrive at the truth,-declare most emphatically, that is your only object; if you can make them believe this, you will have the better chance of leading them wrong. To assist you in doing so, bring forward some one who will declare, that the strength of a steamboiler is " merely a matter of fancy." And do not by any means neglect to try figures; tell the jury" there is a matter of figures to go into," and do your best to bother them that way. For, if any one should be unkind enough to declare in print, that " any pretence to calculate the strength of your boilers would be absurd, or something worse," and give good reasons why, you have nothing to do but to say no more about the "figures," and you are but where you were before you made the attempt.

If an eminent engineer should be called upon to give an opinion of your

boilers, and should disapprove of them, write him a blustering letter, in the hope that his answer may lessen the effect of his opinion on the minds of the jury. (N.B. This last direction is to be used with extreme caution; because his answer may be any thing but such as you wish, and he may insist on its being read to the jury.)

If another eminent engineer gives a clear and decided opinion against your boilers, listen to him with all the patience you can; you will naturally feel very glad when he has said his say, and will not be so foolish as to ask him any questions-you will have had quite enough of him without that.

Throughout the whole business, you will take every opportunity of declaring that your boilers are the very best boilers in the world; and that the more boilers that burst, and the more people they kill, the more you and the company they belong to will feel convinced of their safety. This will make a forcible impression on the jury in favour of your good sense and discretion.

But there is yet a last resource when all other hopes fail. If you can only bring forward some one who may be supposed to know something about the matter, but who, from illness, or being nearly scalded to death, or any other trifling cause, has been unable to appear before the jury until the last stage of the proceedings, you need not despair. You may sooth yourself with the hope, that what he will say, may obliterate from the memories of the jury and the public, the unanimous opinion of all the engineers in the world,-much less in such a paltry place as London.

But, if the jury persist in refusing to be persuaded to think as you wish,why, you will, of course, conclude, they are the most obstinate set of men that could be collected together; and you have nothing left for it, but to yield to your fate with the best grace you may. I am, Sir,

2nd August.

With due commiseration, Your obedient servant,

S. Y., an Engineer.

LONDON MECHANICS' INSTITUTIONCLASSIFICATION OF THE MEMBERS.

Sir,-Widely differing opinions, havbeen very frequently circulated as to the description of persons constituting the members of the London Mechanics' Institution, I beg to hand for insertion in your Magazine the following classified list, recently made out by a sub-committee specially appointed to conduct this investigation.

A similar analysis has been made upon previous occasions by individual members of the institution, but the present is the first official document of the kind that has been prepared. The constitution of some provincial Mechanics' Institutions having appeared in your previous volume, I trust that of the parent establishment will be received with some degree of interest.

Had the particular occupation of the members been more carefully inquired into, from the commencement of the institution, I am confident that the accompanying table would have shown more favourably for the mechanics; but I apprehend, as it now stands, it will bear examination, and is such as can hardly fail to prove satisfactory to all the advocates of general education. The high integrity of the members forming this subcommittee is a sufficient guarantee for the accuracy of their report, which is also to a certain extent corroborated by the results of previous investigations.

The report says, "Your sub-committee have been at much pains, to render their report as accurate as possible; in order to effect this, they have gone over the whole list of members three times, and the result of their investigation will be found in the following report:"

"Some little difficulty has been experienced in classifying the trades, but where several members were found belonging to different branches of one trade, they have all been included in that trade. Thus, for instance, all the various branches of watchmaking, have been included under that head; and the same course has been adopted with other businesses.

"In consequence of such a classification as the present not having been probably expected, all the members, on entering, have not been particularly required to describe their trade or profession. Hence it happens, that a considerable number have given

FLAT CHAMBER BOILERS-SIR JAMES Sir, Mr. Hancock states (page 278), that he has examined the wood-cut and description referred to, in No. 775 of your Magazine, of a patent boiler, and finds that the boiler (Sir James Anderson's) is composed of flat chambers, for which he obtained a patent in the year 1827; and he adds, that as he "has never granted a license to any person to use his said invention for steam-carriages, no person can have a legal right to adopt it." Now, Mr. Editor, this sounds very well; but I will, with your leave, endeavour to show, first, that Mr. Hancock has no patent which gives him a legal

ANDERSONS' AND MR. HANCOCK'S. right to attempt to restrain any person from adopting flat chambers for boilers; secondly, that he has no legal patented right to prevent any person adopting or arranging such flat or any other sort of chambers, in a vertical position, side by side, with spaces between for the caloric and smoke to pass through; and, thirdly, that he has no legal patented right to prevent any person strengthening such chambers in any way he may please, whether by having bolts or rivets through each particular chamber, or by having link-bolts externally round one or more chambers.

In 1824, a Mr. Smith, of London, patented a boiler, for evaporating fluids, composed of two narrow flat chambers, he having previously obtained a patent for a single flat chamber, each composed of thin metal, which were strengthened by having a number of bolts and nuts through the said narrow flat chambers, such bolts being placed about nine inches apart, over its whole surface* (I believe nine inches is mentioned in Mr. Hancock's specification). Again, in 1825, a Mr. J. C. C. Baddaly+ obtained a patent for a boiler for evaporating fluids, which boiler was to be composed of several flat narrow chambers, placed vertically side by side, with spaces or flues between them for the caloric and smoke to pass through, with fire and furnace underneath the chambers.

Mr. Hancock, therefore, whose patent is said to have been obtained in 1827, being two or three years later than the above, cannot legally claim either flat chambers, or the mode of arranging them side by side, with flues or spaces between them, or the mode of strengthening them by bolts, or the fire or furnace underneath,-all these principles being combined and claimed in the above two patents.

I am, Sir,

Your obedient servant,

A SHAREHOLDER IN THE STEAMCARRIAGE COMPANY.

July 31, 1838.

*Smith's (Furnival and Smith's) flat boiler we are acquainted with; it is totally different from Mr. Hancock's. Smith divided his boiler into two flat horizontal chambers, both of which contained water, but the fire was only in contact with the lower chamber, the steam in the upper being generated by the heat of that in the lower. As the partition dividing the boiler into two chambers was of thin metal, cross-ties of iron were used to strengthen it, as well as the top and bottom of the boiler, somewhat in the manner patented by Mr. Russel, and described in our 22nd volume, p. 386.-ED. M. M.

+ Will our Correspondent give us a more particular reference to this alleged existing patent of Mr. Baddaly's? We have examined the register of patents kept in our Patent Agency Office, (for the accuracy of which we think we can vouch,) and can find no such patent as "A Shareholder" mentions. Fearing the existence of a flaw in our list, we likewise caused search to be made at the Inrolment, Petty Bag, and Rolls Chapel offices, in which all specifications are enrolled, but no invention by any one of the name of Baddaly, or of any name at all similar to it, had been specified. We hope that this is an error on the part of our correspondent, and not a wilful attempt at deception, as we were at first inclined to think.-Ed. M. M.

REPORT AS TO THE SAFETY AND EFFICIENCY OF JOYCE'S PATENT HEATING APPARATUS: BY J. T. COOPER, ESQ., &c. AND WILLIAM THOMAS BRANDE, ESQ. F. R. S. PROFESSOR OF CHEMISTRY IN THE ROYAL INSTITUTION.

In compliance with your letter addressed to me on the 10th of March last, I have undertaken an investigation of Joyce's Heating Apparatus, in relation to its heating powers, the quantity of fuel consumed in a given time to produce in an appropriate room a certain increase of heat, also the amount of contamination the air of the room sustains in a certain time, as likewise the deterioration of the air by the combustion of oil, tallow, spermaceti, stearine, and gas, with the view of estimating the comparative injurious effects of Joyce's stoves, and of other methods, by which heat as well as light are produced; and also of the amount of contamination the air undergoes, in places where a number of individuals are congregated, and in which no injurious effects are found to occur.

In the outset I may state, that the room in which the experiments have been conducted, is nearly 14 feet long, 13 feet wide, and 12 feet high, and, consequently, contains about 2000 cubic feet. It has a chimney, and a peculiarly accurately fitted and well constructed register stove, which, when shut, effectually closes its lower aperture. Whenever a particular trial was to be made, bags of sand were placed on the junctions of the window sashes, and also at the bottom of the doors, and every precaution taken to make it as air tight as could be.

I find that one of Joyce's stoves, the internal cylinder of which is six inches in diameter and fifteen inches high, with an inverted cone, having twelve holes, each a quarter of an inch in diameter, burns three ounces of the prepared fuel per hour, when the regulating apertures at the top are quite open; in one instance, with a particular kind of fuel (such as is not commonly sold) it burnt three ounces and 4-10ths. ; but taking the average of a great number of trials car ried on for days, its rate of burning is a fraction less than three ounces per hour; but in all cases the combustion proceeds without producing any of the unpleasant odour that occurs when charcoal of the ordinary kind is burnt in a similar manner.

In one instance, the stove was kindled, and at eleven o'clock in the evening was placed in the above-named room, the temperature of which was 62 degrees Fahr.; the room was then closed, and not entered till ten o'clock the following morning; I ther remained in the room about an hour, the doors and windows being kept closed, and