of the viewers or managers of the colliery were able to explore the extent of the damage occasioned by this explosion?-It was twentythree or twenty-four weeks before they got to the bottom of the shaft, which was so shattered that it required to be repaired, and the atmospheric air to be carried down.

Were there no means of access from any of the other shafts ?-There were none; the other shafts became in the same state very soon.

Then the bodies of the sufferers were not recovered for the space of time that you have named ?—They were not. All the ditches in the "country-side" were stopped to get water to pour into the pit. We had extinguishing or fire-engines brought from Newcastle, and the water was poured in till it came above the fire, and then was extinguished.

This accident was of course attended with severe pecuniary loss to the owners of that colliery, in addition to the destruction of human life?-It was.

At the period of this accident candles only were used. Witness then thought of contriving a lamp (enclosed light) which could be taken into an explosive mixture without exploding externally. His idea was, to produce a strong current through a lamp by means of tubes. The first he made had a tube at the bottom to admit the atmospheric air, or fire-damp and air, to feed the burner or combustion of the lamp, and a chimney at the top to assist the current. This lamp was tried in the mine on the 21st of October, 1815, and it always went out when exposed to a blower of gas; but the lamp required to be carried very steadily on account, as the witness imagined, of the burnt air (as he then called it), or the azotic gas, that lodged round the exterior of the flame. When the lamp was moved backwards and forwards, this poisonous air came in contact with the flame and put it out. It then struck witness that if he put more tubes in he should discharge the poisonous matter that hung about the flame, by admitting the air to the exterior part of the flame. He, therefore, got a lamp made with three tubes, of a diameter considerably less; and this was tried in the mine, November 4, 1815. Found that it would burn much better than the other; but the result was the same as with the first lamp when it was brought into contact with a blower of gas.

These new tubes pointing towards the flame, whenever the inflammable gas came to the point of explosion in the lamp, it ran back to the tubes, but did not go down them, but simply ran from the burner to the tubes, burnt for a short time, and then went out. This proved to witness that the tubes did not require to be so long, because the gas did not actually go into them at all. His next lamp had, therefore, a double perforated plate at the bottom, with the holes considerably

smaller. Still did not know of what size the holes should be, but made them very small. This lamp was tried immediately after November 4, and found to burn extremely well. The principle of the lamp now before the Committee is now precisely the same, though the shape is rather different. It was tried at the Philosophical Society in Newcastle, and certainly before any other lamp had made its appearance. At this time witness had had no access to any scientific works, nor any intercourse with scientific men. Is still more convinced than ever that his lamp, properly constructed, is the safest lamp that could be made use of. So long as the glass keeps whole it never can fill with flame; and though he has seen the glass crack, never knew it fall to pieces in the lamp, as it only cracks to ease the expansion or contraction, and remains safe.

But you do not mean to say that your original lamp of unprotected glass would be equally safe with No. 5, now produced -do you? No, I mean with the wiregauze out-side that it is certainly the safest lamp.

Considers the system of ventilation followed in mines to be very faulty, but does not yet see how it may be remedied. Is not prepared to recommend any better mode than the use of the furnace. But thinks that there might be some instruments kept in the mines to serve as a continual guide to the miner when he goes down. Believes it very rarely happens that accidents have taken place to any great extent but only at the time when the barometer stood low. Now if a good large barometer were kept at the bottom of each mine, which the overlooker, the wasteman, or those that have any charge, should have an opportunity of seeing it, would put him on his guard in some measure to look out for danger. Has made some experiments himself on blowers to prove how this would act. Has gone down when the barometer stood very low; and found some of the blowers or fissures throwing out very great quantities of gas. Has gone again when the barometer has stood high, and the very same blowers that were sending out the quantity of gas when the barometer stood low, was taking in the atmosphere, so that there was not near the quantity of gas. In fact, it is not possible that the quantity of gas can come out when the barometer stands high that does when it stands low, because the atmosphere is varied in its pressure considerably.

Do you think that the small difference of density indicated by 14lbs. an inch and 15 lbs. an inch, would be sufficient to cause diminution or increase of the carburetted hydrogen from the fissure?-I think in one case a very large quantity of gas might come out, and

in the other very little might come out; indeed I know that it is the case.

Then the great advantage which you would anticipate from the use of the tube barometer always in sight of the underviewers and wastemen, would be to stimulate them to an increase of care under certain changes?-I think so. I used to give my instructions to the wastemen in Killingworth upon that very point, and many got barometers from my observations to them.

Are you aware whether they have continued to make observations?—I dare say they do, but I cannot speak to that, not having been among them lately.

Are you aware whether their experience in any way corroborated you?-Yes, I am sure that some of them did; I was so familiar with them, and talked to them about it, and we know that such a change took place.

They acknowledged that the mine was in a fouler state whenever the barometer indicated a diminished pressure of atmosphere? -Yes, and it was a common observation of the wastemen, that the explosion was caused by the south wind, which occasioned this state of the barometer; before they knew any thing of the barometer, that was the observation that they made.

In many mines it not the case that the hewers on turning out and finding a warm south-west wind, decline proceeding to work?

I believe it has been so.

Witness is aware that the electric spark will cause explosions of different mixtures of atmospheric air and light carburetted hydrogen, but does not think explosions in coal mines can ever have arisen from this cause.

You think that the electric spark is never given out below the surface of the earth in sufficient quantity to produce combustion ?— I think there is not the slightest possibility of that, on account of the moist atmosphere, which will not hold the electric spark; it is conducted always down into solids.

Are you not aware that the electric spark has been seen to ascend from the surface of the earth? I do not see the possibility of it.

Is it not so stated?-I cannot say the earth becomes positively charged, and the air or cloud becomes negatively charged, it may be so.

Do you think all the accidents in lighting are caused by the descent of the fluid ?—Yes, probably never the reverse.

Did you ever read this passage? "I found that the common electric spark would not explode five parts of air and one of firedamp, though it exploded six parts of air and one of damp."-Yes, I can easily conceive that such an experiment can be made, but it was by artificial means, it would be by an electrical machine or from a galvanic battery, getting the spark artificially.

Do you consider that that was his opinion on reading further, "But very strong sparks on the discharge of a Leyden jar seemed to have the same power of exploding different mixtures of gas as the flame of a taper." Do you think the descent of the electric fluid into the earth is at all times perceptible? -No, I do not imagine that he is referring there to any discharge of the electric fluid from the atmosphere, but in the Leyden jar, it was then obtained from the electrical machine.

Do you think it never exists in the atmosphere in as concentrated a state as in a galvanic battery?-I think it cannot be, I have tried to collect it with copper wires on a very large scale; I have had 500 yards of copper wire sent up by a kite for the purpose. No electricity could be obtained in damp weather. In the middle of the winter it could always be collected in the greatest quantities, and of such intensity that we could electrify any thing, by the wire merely from the kite.

Do you mean to say that the discharge that throws down a house is not equal to the discharge from a common battery?-Far more so; you might make the battery equal to any thing by increasing the size, but when a house is thrown down, that is a current of electric fluid thrown out of the atmosphere.

Do you consider that such a current would not cause explosion if it came upon a magazine of inflammable gas?-I think it might by descending in that way, if that were possible.

Do you think it quite impossible that such a portion may remain to ignite that magazine below the surface of the earth?-I do.

On what ground do you give that answer! -As soon as ever it reaches the earth it immediately becomes eased by the immense mass that takes it in. I will take a tree that is struck by lightning: the tree is sometimes shattered to pieces, but you do not see the ground disturbed at all, yet the fluid goes into the ground.

Do you consider that the tree, although a conductor, offers any resistance to the passage of the electric fluid, as compared with the atmosphere?-I think it does; when it catches the points of a tree it immediately seizes the tree with great rapidity; while it is acting upon the branches it very rarely 'disturbs the branches, from the immense space occupied by them, but when once brought into the trunk it is frequently shivered to pieces, from the small space it has to pass in.

If conductors on the surface of the earth operate so as to radiate the electric fluid, do you conceive it impossible, that by certain metallic earths it may again be concentrated

and conveyed to a magazine of inflammable gas? Perhaps so.

Do you mean to say that the electric spark cannot be conveyed by conductors into the earth?—I mean to say that it can, and it is; but not in quantities.

Mr. George Upton, Lamp Manufacturer, Cheapside, examined:

Has paid great attention to the subject of the safe lighting of mines. Was induced to go particularly into the examination of it from having been told by his partner, Mr. Roberts. who had been a working miner for twenty-five years, that the Davy-lamp was not safe. After two or three years experimenting, in conjunction with Mr. Roberts, produced a lamp which is wholly free from the defects of the Davy-lamp.

Will you describe to the Committee in what respect that lamp varied from Sir Hum. phrey Davy s?-The lamp of Sir Humphrey Davy's which is in general use, fills with flame inmediately it is placed in an inflammable atmosphere; it receives the air through the meshes of the wire-gauze from the point of the wick to the top of the cage, as it may be required. In our lamp, which I will now produce [the Witness produced the same], the air passes between a layer of wire-gauze and a cone before it can pass from the wick; the cone brings the whole air admitted into the lamp in immediate contact with the flame, or as nearly the whole of it as possible. The consequence is, that the air that passes from the wick has been rendered incapable of supporting flame by that contact, and consequently no other part of the lamp but at or near the wick is capable of supporting combustion; the advantage of which is, that the flame never comes in contact with the wiregauze. It has not power, therefore, to act with force upon the top of the wire-gauze, which is most powerfully acted upon in Sir Humphrey Davy's lamp; the top is the most vulnerable part of his lamp. I should name that in our lamp a glass is put over the wiregauze cage to drive the air under the horizontal layer of gauze below the wick, otherwise it would not pass that way.

Ilow is the air forced down?-It is drawn through certain protected holes by the flame of the wick, the access of air being prevented in all other parts of the lamp by the glass covering. If it were not for the glass, the air would go the readiest way, and pass through the gauze cage as it does in Sir Humphrey Davy's lamp.

How is the air prevented from going through how?-By the glass covering before stated; the current of air passes out of the top of the lamp.

And you contract the upper orifice not

MR. HERAPATH AND HIS RAILWAY THEOREMS.

Sir, The correspondent who figures in your last Number as "A Looker-on" puts one in mind of one of the finny tribe (ordo salmonis) who, when hunt ed to death by torch-light, pokes its head under some convenient bank, in the vain hope that nobody will be able to recognise it by its tail. Who so stupid as not to be able to assign at once to this "Looker-on" his real name and sur. name? Aut Diabolus, aut Herapathius. Close pursued by that brave old Highlander, Iver M'Iver, with spear in one hand and lighted brand in the otherdriven out of one hole after anotherchased from one side to the other, down stream, up stream-pricked and bleeding in a hundred places the fish (a queer one, it must be confessed) has taken, in despair, to the bank at last, thrust its nose in the mud, and turned its tail on the foe! To drop metaphor, Mr. Editor, who but Mr. John Herapath himself would have ventured to say ("an act of justice" he calls it!) that "Mr. Herapath has the merit of having given the first direct solution to the problem of finding the relative velocities of a locomotive-engine carrying different loads on a plane and up different inclines" (which solution is just no solution at all)? Or who but Mr. John Herapath himself could have gone the greater length (still in all modesty) that " no other mathematician COULD have directly solved the problem?" (!!!) Who, again, except Mr. John Herapath himself, would have ever dreamt of talking of the said Mr. John Herapath's "own physical discoveries," seeing that though the world has heard much about such discoveries (from Mr. Herapath himself, as usual), the world has yet to learn what single thing of the least consequence Mr. John Herapath has discovered? Or who but a controversialist of Mr. Herapath's surpassing candour and ingenuousness, would have ascribed

(as "Looker-on" has done) to Iver MIver a theorem for railway velocities which Iver Miver never promulgated? Twice in the course of this discussion has Iver M'Iver distinctly warned your readers, that the true theorem (his theorem, at least) still remained to be given; and it is impossible for Mr. Herapath, or any one, to tell as yet what that theorem may be.

Apropos de bottes.-On the 5th Dec. last a certain "Pailo-Anti H." (so wondrously resembling our present "Lookeron," that one might safely swear they are alter et idem), challenged all the world

to point out in the thirteen letters of Railways, within a fortnight, the cases of intentional and prejudicial misrepresentation on the part of Mr. Herapath," and pledged himself" within another fortnight to answer the charges," and exhibit H. and his aspersions in their true colours." Within less than a fortnight after this bold challenge, that is to say, in the next following Number of your publication, "Miso-Philo-Anti-H." pointed out certain pages in the Mechanics' Magazine (No. 641, p. 133, and 134, and No. 642, p. 167 and 168), where Philo-Anti-H. (or Mr. Herap ith), would find charges touching the Greenwich Railway of as broad and definite a character to refute as any person could desire to grapple with. But though far more than the "other fortnight" has elapsed, within which the challenger pledged himself to give his answer, no such answer has yet appeared; nor, I presume, been received.* How, sir, are we to account for this ?

What else can we infer from the silence of the challenger than that he cannot (on further consideration) refute "the broad and definite" charges brought against him?

As H. has silenced Mr. Herapath on the subject of the Greenwich Railway, So I venture to prophecy will Iver Milver silence him ere long on the subject of his locomotive theorems (about which it will assuredly be found in the end, "the less said the better").

One word before I conclude, by way of grave and (taken as it may be) kindlymeant advice to Mr. Herapath:-If he wishes to sustain (were it not that I might be thought offensive, I should say improne,) the scientific reputation he has acquired, let him in future think a little

• Not received certainly.-ED. M. M.

before he writes-think less of himself, and more of others-(for it were unjust to nature to suppose that all genius and wisdom are centred in one individual)— look upon the cause of truth as something even dearer than self-glorification -eschew all paltry shifts and still pal. trier disguises, when proved to be in error (as even the best of frail mortals may occasionally be) and be ever as ready in his own proper person to pay to reason the homage of a willing submission, as to share personally in her triumphs.

I have the honour to be, Sir,
Your most obedient servant,
F. M. MEREDITH.

Cambridge, Jan. 19, 1836,

NOTES AND NOTICES.

The Comet.-M. J. Muller, assistant in the Ob servatory here, again saw Halley's comet on the night of the 31st of December. It was very faint indeed, but precisely in accordance with the calcnlation of Professor Gautier, Director of the Observatory. M. Muller directed his telescope at the minute given to the spot designated, and saw the comet really appear, and pass across the objectglass. This was on the 31st of December, at night, at 12h. 45m. 15 1-7 sec. astronomical time; or 5. 56mm, January 1, civil time; right ascension, 16.18.; and south ascension, 24.44.- Geneva, Jau. 4.

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Chimney Cowl." In your 610th Number, there is a cow stated to be invented by an ingenious friend of Mr. L. H. Mundy. If Mr. Mundy will refer to your 2nd vol., August 7, 1824, he will, I think, find that he has been forestalled. It is there stated to have been copied from a French frigate by Captain Warren, R. N.

Communications received from Iver M'Iver (100 late for this week)-Mr. Pine-Mr. R. SimpsonMr. Brackenbury-An Old Mechanic.

The Supplement to the last volume, containing title, index, &c. and portrait of Charles Vignoles, Esq., C. E., is just published, price 6d. Also, the volume complete, in boards, price 9s. 6d.

Patents taken out with economy and despatch; Specifications, Disclaimers, and Amendments, prepared or revised; Caveats entered; and generally every Branch of Patent Business promptly transacted. Drawings of Machinery also executed by skilful assistants, on the shortest notice.

LONDON: Published by J. CUNNINGHAM, at the Mechanics Magazine Office, No. 6, Peterborough-court, between 135 and 136, Fleet-street. Agent for the American Edition, Mr. O. RICH, 12, Red Lion-square. Sold by G. G. BENNIS, 55, Rue Neuve, Saint Augustin, Paris. CUNNINGHAM and SALMON, Printers, Fleet-street.