The best radiators do not appear to belong to any particular class of bodies; litmus blue and Prussian blue are side by side, while sulphuret of lead, and the bi-sulphuret of tin, are fifteen numbers apart.

If the results be admitted as decisive of the radiating powers of the bodies used, they show that each substance has a specific power not depending upon chemical composition, nor upon colour. I do not claim to found such a conclusion upon the experiments; their object has been before stated, and if they shall prevent the introduction of an inference from an imperfect induction, as a law of science, the labour bestowed upon them will be amply recompensed.*

PARLIAMENTARY EVIDENCE ON ACCIDENTS IN MINES. (Continued from p. 319.)

Examination of Mr. George Upton, continued :

And you make the orifice sufficiently large for that purpose?—Yes; it need not be nicely calculated; if it were a little more close or a little more open, it would not, perhaps, make much difference in the action of the lamp. An objection has been made which, perhaps, I may allude to, that it is a disadvantage the glass being on the outside: it was determined to place it on the outside, after a great deal of consideration and a great many experiments. It was found that the glass was in less danger from any external accident than from the risk of coming in contact with the flame; for if it were inside, and the lamp were to be put in a small degree out of the perpendicular, the flame would come in contact with the glass, and would be very likely to break it. Another advantage of the glass being outside the gauze, which is not very immaterial, is, that it keeps the wire-gauze clean, and free from the floating dust which, I am told, is a very great inconvenience, and sometimes chokes up the meshes of the wiregauze.

Suppose the glass to be perfect for the effect for which you use it, causing the current of air to pass down the lamp, what is the advantage of the gauze above the lamp? -The gauze is put there in case of an accident, such as the glass breaking; it would otherwise do as well without. In fact, the first lamps Sir Humphrey Davy made were entirely without wire-gauze; he did not then seem to have any notion that wire-gauze was necessary. Concentric rings were placed both at the top and the bottom of the lamps referred to; and I believe this omission of the wire-gauze in them led to the contention

The scientific reader need not be reminded that these remarks do not bear upon the radiation or absorption of heat accompanying light.

between him and Mr. Stephenson, or Mr. Stephenson's friends, as to the validity of his (Sir H. Davy's) claim on that point.

Supposing the glass to break, the lamp is subject to all the accidents of a Davy-lamp? -Yes, it becomes a Davy lamp at once, and is no worse or better, except that it has perhaps this advantage: the gauze having been less liable to accident from its previous covering, is likely to be more perfect than the gauze of the Davy-lamp, which is daily and hourly exposed to external friction and accidents. It being of a very delicate nature, it is very likely, and I have no doubt very frequently is subject to small derangements in its texture, which may escape the eye of the person whose duty it is to inspect it.

Then none of those disadvantages would arise to the Davy-lamp, with the common glass over it? The common Davy-lamp would go out with the glass over it.

As far as keeping it clean?—Yes; but it would not act with a glass, and therefore a glass could not be so applied.

The principal advantage of your lamp is, that the air which enters the lamp is directed downwards?-Yes, in its way to the wick.

You also attach value to the rising cap, as being readily calculated to admit just a sufficient quantity of air, either of the atmosphere or combined with carburetted hydrogen, to preserve the combustion in the lamp? -Yes. [The Witness lighted the lamp.] The Committee will observe that the taper will not burn with the wick as in the Davy-lamp.

Then, by the experiment of lighting the two, taper and wick, which you have just performed, under the glass, you exhaust the supply of air merely sufficient for one, and thus demonstrate the advantage of the surrounding glass chamber, as depriving the lamp of any obnoxious vapour from the surrounding parts of the mine?—Yes.

Suppose the flame of the wick were near the top of the lamp, would not the gas reach it and be dangerous?-This is prevented by the following means: The flame of the wick, when acted on by inflammable air, instead of coming with any force against the top of the lamp, as with the Davy-lamp, rises merely as a smoky column, gradually narrowing at its extremity. The fact is, that flame cannot live with any force in an atmosphere of this kind: this has just been shown by the taper going out, while the wick continued burning, consequently the iron wire could not get red hot in such a situation.

Is not the heat of that part of flame which is not visible often stronger than that which is visible?-In some cases where it is least seen it is so, but not in this.

Supposing the extension of the flame, which always takes place in carburetted hydrogen, and that part of the flame which is not visi

ble, which has greater heat than that which is visible, might not the gas explode in that point? The flame could not, in such a case, get through the double cap of wire-gauze, as the wire-gauze cap would be protected by the continual passage of air through it not capable of supporting flame.

You are aware that that part in a blowpipe beyond the visible flame is the hottest? -Yes; but the blow pipe has the advantage of pure atmospheric air, while the flame in this lamp above the cone which surrounds the wick, has all the disadvantage of meeting air that will not support combustion, at least, not to any great extent; consequently the Alame would, under such circumstances, be very feeble.

But much more air comes from below the light than is required to keep the light burning? Yes; but its power of supporting flame has been taken from it by its previous use, for it is a known chemical fact, that air that has supported ignition will not again support it.

In all the experiments before alluded to, you of course made use of fictitious gases, prepared for the purpose?—Yes.

Have you ever tried your lamp with the carburetted hydrogen as evolved in the mines? -Yes.

Were the results similar? They were similar as to the flame passing; but to my surprise and to the surprise of the persons present, it passed much more quickly than carburetted hydrogen. The fire-damp, instead of appearing to be the least inflammable of combustible gases, as far as could be judged by its effects upon the lamp, appeared to be quicker in its action in passing through the wire-gauze, which became heated to a white heat almost in an instant.

In that case you must have forced the current with a very strong impetus upon the gauze-Not more than Mr. Roberts considered that a blower might force it. This experiment was tried in a coal mine near Dudley; there were at least twenty miners present.

That is, supposing it had been close to the blower?-Yes. I have emitted to mention one circumstance, which is, perhaps, aaterial in this inquiry. A meeting in March, 1834, of about forty of the principal mine owners of the county of S'affordshire took place at the gas-works at West Bromwich, to witness experiments on the Davy-lamp and the new lamp: these gentlemen had heard with surprise that the Davy-lamp was an insecure instrument, and nothing but ocular demonstration would convince them of the truth of this assertion. As they had been apprised by letter of the purport of the meeting several days previously, they were prepared with a number of lamps which they

had been in the habit of using in the mines, as far as those lamps are used in Staffordshire, which is very limited. They had also a number of their men present; they were most of them persons of long experience in working coal mines. When they saw that none of their lamps would sustain the action of a jet of gas, they were much surprised, as the lamps had hitherto been considered safe.

From all those experiments, and assuming the fact that the damp found in the mines is still more explosive than the fictitious gases obtained by chemical preparation, you have come to the conclusion that Sir Humphrey Davy's lamp, undar certain circumstances, is not a safe instrument?—I consider that Sir Humphrey Davy's lamp, in most of the uses which he recommends it for, and which uses have been sanctioned by several gentlemen of great experience, is extremely dangerous, and must lead occasionally to such catastrophes as those which have occurred lately at Springwell and Wallsend collieries.

And the only contingencies that you apprehend as likely to create danger in your own lamp, is the fracture of the glass and of the gauze, and the burning of the top of the lamp? The burning of the top of the lamp I think impossible, from the experiments I have seen, and from the nature of the atmosphere at the top of the lamp.

Then the only contingencies are, the destruction of the lamp, that is to say, a fracture of the glass and a fracture of the gauze? -Yes.

Do not you think that very much depends upon the size of the aperture at the top of the gauze?-No; the cap or cone immediately surrounding the wick has an opening at the top, and that circumscribes the size of the flame of the lamp, when filled with inflammable air. If that aperture be an inch in diameter, the flame would be an inch also in diameter; if it were half an inch, it would be half an inch only; and if it were two inches, the flame would be two inches. That is the only part of the lamp in which there need be any great exactness, and that exactness merely relates to having a proper space between the wire gauze and the flame of the wick.

Supposing there were no glass at all, would not your lamp be equally safe with that aperture?-No; the lamp would then fill it with flame, as the Davy-lamp does.

The principle then is, that the supply either of atmospheric air, or combined with light carburetted hydrogen gas, is equal, and no more than adequate, for the supply of the wick?-No, that is not the principle which we have made the lamp upon; it might be regulated on such a principle, if necessary. The point which we have had in view, and which we have considered all that is neces.

sary, is to make the aperture sufficiently large to let the air pass from the wick.

Supposing there were some difficulty in the current going under the flame, if the opening at the top were sufficiently large, might not another current go by the sides of the glass, while the current from the lamp went up the centre? The lamp would go out in that

case.

The result of your experiment is such as to lead you to believe that too much is attributed to the ignorance and carelessness of the miner, and too little to the dangerous circumstances in which the lamp is placed?I believe so.

Will you describe what the general opinions of the miners are as to the safety and the light of the lamp? In Staffordshire there is one universal opinion as to its safety. I did not meet with a single instance of any person who had the least doubt of its safety; but the miners in Staffordshire, particularly in the very thick seams, do not work with it.

Have you ever in any place had a conversation with the men as to the light given by the Davy-lamp?-Yes; they stated that it was quite inadequate for the purpose for which they wanted it in the thick mines, to give them such a light as they could work by. I beg to observe, that the light of the Davylamp cannot be increased without destroying its safety, even as far as it now extends. It is known that the heat of the flame is according to its bulk, and the consequence would be, that if Sir H. Davy had increased the cylinder of his wire-gauze lamp to the extent necessary for a larger wick, the power of such a body of flame would be so great as to oxydize or to burn the gauze to pieces in a short time.

Have you ever conversed with the men in the north of England, where it is used, as to the light given by the lamp compared with candles?-No, I have not; in the thin seams much more tight would be got from it than in the thick ones. The men were very anxious to get a better light than the Davy-lamp gave them. They were very anxious to work with lamps on account of the known or supposed safety of them over candles, but they found it impossible, as I have before stated, to work with the light of the Davy-lamp in the thick mines.

Mr. John Buddle, Coal-Viewer, examined:

Produces a diagram, showing a plan of the workings of the Bensham seam at Wallsend colliery, at the time the explosion hap. pened, on the 23rd October, 1821, when fifty-two lives were lost.

To what extent had those workings been conducted at that period?-There was not one place in the pit 100 yards from the bottom of the shaft. I found the seam pro

digiously fiery, so much so that the coal itself afforded gas enough to light the pit.

Was that independent of any particular fissure or brack?—Yes; I simply drilled a hole into the solid coal and stuck a tin pipe into the aperture, surrounded it with clay and lighted it, and I had immediately a gas light; the quantity of gas evolved from the coal was such, that in every one of those places I had nothing to do but to set a candle, and then could set a thousand fissures on fire; the whole face of the working was a gas-pipe from every pore of the coal, and when the shots were fired for blasting down the coal, they generally set fire to the gas as it was evolved from the coal. The men had what we called dusters or wet sacks on their jackets, by which, as soon as the gas began burning, they knocked the flame out, but sometimes that might not be sufficient, and in this very pit I had in the main-coal seam two cannons, because I found concussion the best mode of putting out flame, when inaccessible to dusting.

What size were those pieces ?--I had them made of a peculiar construction; they are made of malleable iron, and the bores are conical, about two inches and a half in diameter at the muzzle; the depth of the barrel is not more than fourteen inches, and we charge them the same as charging a shot, that is, we put in a quantity of powder, and stem or tamp them with oakum driven down by a heavy maul, the object being concussion.

What quantity of powder would you insert? I should suppose about half a pound, from a third to half a pound.

And this you have found successful in extinguishing fire?-Yes, I have extinguished gas fires that were not accessible by any possible means; it is a thing which I think ought to be generally known, because the immense concussion will knock out the flame of inflammable air when it is not accessible. I have succeeded in the top of one of those gasometers when the flame has run into the goafs or wastes, by explosion of one of those guns, and have thus shaken the flame out. My under-viewer performed a very clever feat some months ago in the Bensham seam at Wallsend; I gave him the highest credit for it it occurred in a stow-board.

What do you mean by stow-board?-A place to deposit rubbish in, to avoid the expense of bringing it up the pipe; we were making a railroad between two dykes, which required the blasting down of the roof.

That is to obtain head room?-Yes, for the horses, and also for the deposition of rubbish from several adjacent parts of the mine. The Davy-lamps were used by positive orders during the stowing up of the board; however at last, when the board was nearly filled up, the stower came with his

candle too near to the stones or end of the stowing; the gas oozing out of the stowboard from amongst the rubbish, caught hold of his light, and filled the interstices of the stowing with fire instantly, although there was a full current of air passing the boardend at the same time. It blazed furiously, and they could not get access to it; it was blazing out all across the place: it was about half-past two in the morning; I was called; the under-viewer had gone down, and he sent his son, the overman, to tell me the dilemma they were in, and wished to know what was to be done. I made the best of my way to the place, and when I arrived within a very little distance, I met some men who gave me the welcome intelligence that the fire was out. I came up to the place, and found a great quantity of smoke as I approached the place, and the men that were working in the current of air to leeward had been driven out by the strength of the smoke and after-damp. This fire was about five yards broad, and came flashing out of the top of the stowing, and the flame was playing backwards and forwards, sometimes apparently out, and then re-appearing again. When I came, I asked Mr. Atkinson," how have you managed this?" and he said, "I knew the guns were not at hand, and I drilled a large hole into the rock on the right hand of the board, and made a gun of it." He put a large charge of powder into this hole, and about half stemmed or tamped it; he then exploded it, which produced the desired effect, as it instantly extinguished the flame. I gave Mr. Atkinson very great credit for his tact on this occasion; it showed great knowledge and judgment of the subject, and he effected by this expedient what there would have been great difficulty in accomplishing by any other means.

Is not the Bensham seam considered the most dirty seam you have?-It is, because it has been but partially worked as yet in the country.

Do not you imagine that that seam will become more safe as it is more explored ?—I have no doubt but it will become more pure, because all the pillars that are standing firm become exhausted of gas in this colliery; each coal pillar, taken individually, after a certain time exhausts itself of its gas. It is very singular that this seam is only so fiery just on the north side of the Tyne. I speak of my own knowledge of the adjoining colliery of Jarrow, in the same seam; in the north part of the Jarrow colliery, which adjoins Wallsend, it is as fiery nearly as Wallsend; but at a few hundred yards to the south of Jarrow pit there is comparatively little inflammable air; and again, at the Manor Wallsend colliery, I am told that there is a very trifling quantity of gas.

Is there any fault between that part of the

mine which is most fiery and the other side which is not fiery ?-Yes; and I can speak more particularly to Jarrow: it is a fault, a slip-dyke, which makes a line of demarcation between the foul part of the mine and the comparatively clean part.

May not explosions occasionally result from the sudden discharge of electricity?—They may, but I have never known an explosion from lightning, except when it ignited the gas at the top of a pit. The Lawson mine pit was exploded by lightning; it is upwards of seventy fathoms; but the explosion took place at or above the surface; the pit itself had become a gas-pipe; something had happened, which I do not immediately recollect, to derange the ventilation. I had nothing to do with the colliery at the time, but I happened to be near the pit during the thunderstorm. The ventilation having been deranged, as already stated, the whole of the workings below were filled with gas, as well as the shaft, and consequently the shaft itself became a gas-pipe, and was then discharging what was generated below. This discharge was ascending in a current from the mouth of the pit when the thunder-storm came on; a flash of lightning ignited the gas, and a very heavy explosion immediately ensued.

Was there a current of atmospheric air passing through the mine at that time?No, there was no ventilation in the pit at that moment.

Is it not known that carburetted hydrogen will not explode without a mixture of atmospheric air?-Yes.

How could the carburetted hydrogen which was in the pit explode, unless there was a current of air?-Because in such a case it supplies itself with a sufficient quantity of air to make it explode. If you fill a bottle with this gas and set fire to it at the mouth of the bottle, as long as there is an outward pressure it keeps burning at the mouth, but by-and-by it creeps down into the bottle, supplying itself with as much air as keeps it burning for awhile, and then explodes. I have known a pit shut up for three weeks as close as we could make it; the coal was of fire below, and we thought we had it sufficiently fastened up to prevent explosion, but at the end of three weeks it exploded, although the fire below could only have been supplied with fresh air through the fissures in the rubbish at the top of the pit.

You state this to show that it is impossible to prove how much atmospheric air may be supplied under those circumstances?—Yes; but it supplies enough to produce explosion. I went to see the havoc that had been made at the Lawson main pit, and had been there a short time, with a great number of other people, when another explosion, a most furi

ous one, took place, when I was within eighteen feet of the top of the pit.

How far had the explosion passed into the workings?—I should conceive but a short distance; indeed, there was not much space below.

The explosion was in the pit?-Yes, and in part of the workings. There might be an interval of an hour and a half between the two explosions.

Was the explosion so immediate upon the flash of lightning as to leave no doubt of the lightning being the cause?-I cannot state the interval between the flash and the gas being perceived to be ignited, but I understood it to be instantaneous.

Have you ever thought of the possibility of the electric fluid descending through the earth, conducted by any metallic vein or otherwise, in such a body as to occasion subterranean explosion?-I have no reason to believe that it has occasioned subterranean explosion; but I know a fact, recorded by my father, of the engine-pump having acted as a conductor, and carried the electric fluid to the bottom of the pit.

And what were the consequences, as he described them? Nothing injurious; the fluid ran down the pumps into the water at the bottom of the pit, and nothing excepting a considerable noise was occasioned.

What would your theory be, if the bottom of the shaft was in a foul state?-Explosion immediately, because in certain circumstances the gas may be fired by the electric. spark.

Are the lamps in general use in the county of Northumberland made by the best lampmaker in the town of Newcastle, Mr. Watson? They are. I lately had reason to find fault with the manufacture of some lamps, and more especially with the gauze; that is not very lately, perhaps twelve months ago; for people were going round selling gauze cheap, which was not what it ought to be; and from that time I have found it useful to carry a piece of standard gauze in my pocket, one inch square, with a small lens, which enables me to examine the state of the gauze and cylinders accurately. When there is any doubt that the gauze is not the proper thing, my small lens (the same as is used by the Paisley manufacturers for examining their muslins) enables me at once to ascertain if the gauze is of the right sort. There is an aperture of a quarter of an inch square in the frame of the lens, which forms a proper gauge for the meshes of the gauze. This is a piece of the standard wire-gauze of the right size, and by placing this little instrument so, and looking through the lens, you may count the number of apertures in a quarter of an inch as a multiple for a whole inch; that is what I call my gauze gauge.

The Committee will see by the lens that there is a kind of indentation that prevents the movement of the wires where they decussate when the workmen brushes the inside of the cylinder to clean it, so that he cannot displace the gauze by any ordinary application of the brush.

Was there any other defect in the gauze? -The irregularity of the interstices is to be apprehended. By placing the lens upon the cylinder in any lamp I immediately perceive whether the gauze is regularly made, and if it is in good order. The number of apertures per square inch in that standard size is about 784; it may vary between that and 800.

Have you ever met with any gauze so slightly constructed that the indentations you have spoken of were by no means perfect?— I have not examined any lately, for I have repudiated the whole of that sort of gauze; if it differs from the standard I do not allow it to be used, and I have prohibited the use of any such gauze. I have samples at every one of the shops where our Davy-lamps are repaired, with the strictest injunctions that no other gauze is to be used but what corresponds with that sample.

Is this gauze that you have made the one originally prescribed by Sir Humphrey Davy? -I think it is, as near as may be. I do not at this moment recollect the number of apertures which he prescribes; it depends upon the size of the wire; but in my very extensive practice I have found this to be perfectly safe.

But you have reason to suspect that imperfectly woven gauze is in use in certain places ?-I believe it is. I have not been in any part of the kingdom, with the exception of Whitehaven and Workington, in the collieries, where the Davy-lamp seems to be considered a working implement; it is rather considered as a matter of curiosity or precaution to inspect certain places of the mine, to discover where gas may be found, rather than considering it as a working implement belonging to the mine. Now we consider it as an actual implement of our trade, as much as a pick or a maul; and hence it is that we have it under very strict regulation, and, I flatter myself, very good management. I may state that the number of Davys used in the collieries that I am immediately connected with varies from 1,000 to 1,500 in daily use; in the Marquis of Londonderry's collieries alone there are nearly 900 in daily

use.

Having that large number constantly under your notice, what should you describe as the accidents to which they were most liable in their use?—Nothing, I conceive, but violence or injury arising from some extraneous cause. In nearly twenty years' practice I