Sir H. Davy's Safety Lamp.

THIS Lamp of Safety, for coal mines, is the invaluable and splendid invention of Sir H. Davy. We shall here describe its construction.

In the parts of coal mines where danger was apprehended from fire-damp, miners had been accustomed to guide themselves, or to work, by the light afforded by the sparks of steel, struck off from a wheel of flint. But even this apparatus, though much less dangerous than a candle, sometimes produced explosions of the fire-damp.

A perfect security from accident is, however, offered to the miner in the use of a safe lamp, which transmits its light, and is fed with air, through a cylinder of iron or copper wire gauze; and this fine invention has the advantage of requiring no machinery, no philosophical knowledge to direct its use, and is made at a very cheap rate.

The apertures in the gauze should not be more than one-twentieth of an inch square. As the fire-damp is not inflamed by ignited wire, the thickness of the wire is not of importance, but wire from one-fortieth to one-sixtieth of an inch in diameter is the most convenient.

The cage or cylinder should be made by double joinings, the gauze being folded over in such a manner as to leave no apertures. When it is cylindrical, it should not be more than two inches in diameter; for in larger cylinders, the combustion of the fire-damp renders the top inconveniently hot; and a double top is always a proper precaution, fixed one half or three quarters of an inch above the first top.

The gauze cylinder should be fastened to the lamp by a screw of four or five turns, and fitted to the screw by a tight ring. All joinings in the lamp should be made with hard solder; and the security depends upon the circumstance, that no aperture exists in the apparatus, larger than in the wire gauze.

The parts of the lamp are,

1. The brass cistern which contains the oil, pierced near the centre with a vertical narrow tube, nearly filled with a wire which is recurved above, on the level of the burner, to trim the wick, by acting on the lower end of the wire with the fingers. It is called the safety trimmer.

2. The rim, in which the wire gauze cover is fixed, and which is fastened to the cistern by a moveable screw.

3. An aperture for supplying oil, fitted with a screw or a cork, and which communicates with the bottom of the cistern by a tube; and a central aperture for the wick.

4. The wire gauze cylinder, which should not have less than six hundred and twenty-five apertures to the square inch."

5. The second top three quarters of an inch above the first, surmounted by a brass or copper plate, to which the ring of suspension is fixed.

6. Four or six thick vertical wires, joining the cistern below with the top plate, and serving as protecting pillars round the cage.

When the wire gauze safe lamp is lighted and introduced into an atmosphere gradually mixed with fire-damp, the first effect of the fire-damp is to increase the length and size of the flame. When the inflammable gas forms as much as one-twelfth of the volume of the air, the cylinder becomes filled with a feeble blue flame, but the flame of the wick appears burning brightly within the blue flame, and the light of the wick augments till the fire-damp increases to one-sixth or one-fifth, when it is lost in the flame of the fire-damp, which in this case fills the cylinder with a pretty strong light. As long as any explosive mixture of gas exists in contact with the lamp, so long it will give light, and when it is extinguished, which happens when the foul air constitutes as much as one-third of the volume of the atmosphere, the air is no longer proper for respiration; for though animal life will continue where flame is extinguished, yet it is always with suffering. By fixing a coil of platinum wire above the wick, ignition will continue in the metal when the lamp itself is extinguished, and from the ignited wire the wick may be again rekindled, on going into a less inflammable atmosphere. "We have frequently used the lamps where the explosive mixture was so high as to heat the wire gauze red hot; but on examining a lamp which has been in constant use for three months, and occasionally subjected to this degree of heat, I cannot perceive that the gauze cylinder of iron wire is at all impaired. I have not, however, thought it prudent, in our present state of experience, to persist in using the lamps under such circumstances, because I have observed, that in such situations the particles of coal dust floating in the air, fire at the gas burning within the cylinder, and fly off in small luminous sparks. This appearance, I must confess, alarmed me in the first instance, but experience soon proved that it was not dangerous.

"Besides the facilities afforded by this invention, to the working of coal mines abounding in fire-damp, it has enabled the directors and superintendents to ascertain, with the utmost precision and expedition, both the presence, the quantity, and correct situation of the gas. Instead of creeping inch by inch with a candle, as is usual, along the galleries of a mine suspected to contain fire-damp, in order to ascertain its presence, we walk firmly on with the safe lamps, and, with the utmost confidence, prove the actual state of the mine. By observ

ing attentively the several appearances upon the flame of the lamp, in an examination of this kind, the cause of accidents which happened to the most experienced and cautious miners, is completely developed; and this has hitherto been in a great measure matter of mere conjecture.

"It is not necessary that I should enlarge upon the national advantages which must necessarily result from an invention calculated to prolong our supply of mineral coal, because I think them obvious to every reflecting mind; but I cannot conclude without expressing my highest sentiments of admiration for those talents which have developed the properties, and controlled the power, of one of the most dangerous elements which human enterprise has hitherto had to encounter."-See Letter to Sir H. Davy, in Journal of Science, Vol. I. p. 302. by John Buddle, esq. generally and justly esteemed the most scientific coal miner in the kingdom.

Dillon's improved Safety Lamp.

MR. DILLON has lately introduced to the notice of the scientific world, an improvement upon the Safety Lamp of Sir Humphry Davy, which appears to us of sufficient interest for illustration. As the Davy Lamp is too well known to need special description here, it will be merely necessary to allude to the principle of the invention, in order to point out Mr. Dillon's improvement.

He maintains, in opposition to Sir Humphry Davy, that the Davy lamp acts by its heat and rarefaction, and not from Sir H. Davy's theory, that flame is cooled by a wire-gauze covering. He shows, by a simple experiment, that the Davy lamp is not safe in a current of hydrogen or carburetted hydrogen gas, and that many lives may have been lost from the confidence of miners in its perfect safety. A current of hydrogen or carburetted hodrogen gas steadily directed on the flame of the lamp from a bladder and stopcock, by cooling the wire gauze, brings the flame of the lamp through the gauze to the mouth of the stopcock (even should there be six folds of gauze intervening.) He shows also, by immersing the lamp, when cold and newly lighted, into a jar of dense hydrogen or carburetted hydrogen gas, or an explosive mixture with atmospheric air, that explosion takes place inside and outside of the lamp; whereas, when the lamp has burnt sufficiently long to heat the wire gauze, no explosion takes place on the outside of the lamp. These experiments appear incontrovertible in support of his theory, which is, "that the wire gauze is merely the rapid receiver and the retainer of heat, and that it is the caloric in its meshes which prevents the flame of the lamp from being fed by the oxygen of the atmosphere on the outside."

The experiments of Libri, showing that flame is inflected by metallic rods, and that "when two flames are made to approach each other, there is a mutual repulsion, although their proximity increases the temperature of each, instead of diminishing it," support Mr. Dillon's theory-the inflection being occasioned by the rarefaction of the air between the rod and the flame, the latter seeking for oxygen to support it in a denser medium, the two flames repelling each other for the same reason, and not from any mysterious and "repulsive effect of the wires of the gauze tissue." Mr. Dillon increases the heat of the lamp, and places on it a shield of talc to protect it from a current, and, upon his theory, the shafts or workings of iron and coal mines may be lighted with gas with perfect safety, protecting the flame with wire gauze and a circular shield of talc.

We have been favoured with the following letter, on the subject of the Fire-damp and Sir H. Davy's Safety Lamp, from the learned Chemist and Lecturer, Mr. Murray, F. S. A. F. G. S., &c. &c.

Sir,

Derby, 1st October, 1828.

Agreeably to your request to me, I beg now to give you a few cursory remarks on the production of fire-damp (the protocarbonated hydrogen of modern chemists) in mines, and Sir H. Davy's Safety Lamp.

Davy ascribes, as Mr. Langmire had done before him, the production of fire-damp in coal mines to the high pressure under which it is assumed coal has been formed. All this, however, is vague conjecture; and hypothesis happily now receives but little attention or respect, and this dogmatism, in reference to the first creation of coal, but ill becomes the character of those who assume the Philosophy of Bacon as the standard of appeal in matters of Science. As the fire-damp is most abundantly liberated in the vicinity of faults or dykes which abrupt the strata and crumble the coal, it seems to me most accordant with observed facts to ascribe the liberation of fire-damp (from the coal itself) to their mechanical agency —and cæteris paribus the amount of this accumulation in coal mines will be in some ratio with the numerical amount or extent of such dislocations. Thus, too, a piece of coal, simply broken under water, will evolve bubbles of this inflammable gas.

I was the first individual who ever proposed a safety lamp for mines. Its principles were founded on the low specific gravity of the carbonated hydrogen. It was an air-tight lamp, supplied with air from the floor of the mine. This proposition will be found in the first edition of my Elements of Chemical Science, published in June, 1815, and in November following the late Dr. John Murray, of Edinburgh, adopted the same plan. In reference to the principal of safety in Sir H. Davy's wire gauze lamp for mines, it is assumed by its inventor that it is entirely and exclusively dependant on a presumed cooling influence. This view of it, however, is at best problematical, and is one which I have combated from the period of its introduction to the mining world. Having had the wire gauze which composes the cylinder red hot in the fiery wastes of the mine, I do own I cannot comprehend an idea of cooling influence as applicable to red hot wire, and I moreover formed a safety cylinder of muslin, having previously dipt it into phosphate of ammonia to prevent its ignition by flame, and this I proved to be equally safe with the wire gauze.

Towards the close of last year I gave a course of Chemical Prelections in Belfast, wherein I stated these views, accompanied also by new illustrations on the structure and phænomena of flame. Since that period I perceive that a gentleman (Mr. Dillon) of that town has much improved the safety lamp of Sir H. Davy by the attachment of a semicircular shield of talc, which prevents the cooling of the wire gauze by forming a countercheck to the current of

the mine.

The phænomena of safety appear to me ascribable to a compound cause-the rarefaction by heat of the gaseous elements of explosion and an admixture of a portion of the products of combustion evolving from the flame of the wick.

The truth is, that the safety lamp, when first lighted and the wire gauze is coldest, is unsafe, but when heated it is on the contrary safe.

From a very early period of the enquiry I pointed out the great danger which would ensue from using copper wire gauze as the cylindrical tissue of the safety lamp. Iron wire must be alone employed, since I found that the flame of the fire-damp assumed a green tint when burning within a safety lamp constructed of copper wire, and in one instance, in my hands, it had nearly burnt its way out.

Mr. Glover.

I am,

Sir,

Yours most obediently,
J. MURRAY.

Having resided upwards of eight years at Wirksworth, the capital of the mineral district in this county, and having during that time received the friendship of some of the principal lead merchants and agents, and experienced the civility of all the miners, I feel interested for their welfare; this induced me to give as full an article on the mines as the limits of this volume would permit; to extract the particulars of Sir H. Davy's Safety Lamp from Dr. Ure's Chemical Dictionary, and to make an application to the eminent lecturer and chemist Mr. Murray, (whose obliging answer to my enquiries is given above) with a view of being instrumental in giving every possible publicity to an invention, calculated to lessen one of the dangers to which the industrious miner is so frequently exposed. I also hope our article on the mines and minerals, the documents we have selected, and the list of lessees of mines under the crown, from an early date, (though not so perfect as we could wish) furnished by my friend Mr. Thomas Norris Ince of Wirksworth, (to whom we are much indebted for other valuable communications,) may not be uninteresting to many of my friends connected with the lead mines. Before I conclude this division of the work, it is but due from me to declare, to the credit of that numerous body of men, employed in the mines in the wapentake of Wirksworth, and the High Peak in this county, that, I am convinced, not a more honest, civil, moral, and laborious class of men, ever existed in a community. At the celebration of the general peace in 1815, at Wirksworth, nothing afforded me a greater grati

fication on that day of rejoicing amongst the cavalcade, than the sight of a company of these hardy veterans, who had stood many a blast during the war, and had been instrumental in furnishing their king with deadly weapons,+ equipped in their mining dress, and carrying the emblems of their calling, viz. their venerable men the books of law, containing their ancient rights and customs, preceded by flags and a band of music, and the more athletic their mining tools, such as picks, buckers, nogers, skewers, &c. slung about them, which had a very formidable and novel appearance.

That the mines which has through so many centuries furnished employment to the labourer, and riches to the proprietor, may still continue to flourish to the end of time, is the sincere wish of the Publisher.

Copy of the Roll of Battell Abbeie, and a List of the Noble Captains who assisted William the Conqueror to subdue this Isle.

IT may probably afford some amusement to give a list of the names of the noble captains and gentlemen who came over with, and assisted king William in the conquest of this land. They are to be found in the Chronicles of Normandy. Holinshed has preserved a copy of the Catalogue and Roll, from which the following list is extracted:

"A Catalog of such noble men, lords, and gentlemen of name, as came into the land with William the Conqueror.

* The miners are daily exposed to danger in blasting the rocks with gunpowder.

Le seig. Doriual
Le seig. de la Hay
Le seig. de S. John
Le seig. de Saussy
Le seig. de Brye
Richard Dollebec
Le seig, du Monfiquet
Le seig. de Bresey
Le seig. de Semilly
Le seig. de Tilly
Le seig. de Preaux
Le seig. de S. Denis
Le seig de Meuley

Le seig. de Monceaux

The Archers of Bretuile
The Archers of Vaudreuile
Le seig. de S. Sain
Le seig. de Breansou
Le seig. de Sassy
Le seig. de Nassy
Le vidam de Chartres
Le seig. de Icanuile
Le vidam du Passais
Pierre du Bailleul, seig. de
Fescampe

Le Seneschal de Torchy
Le seig. de Grissey
Le seig. de Bassey

Le seig. de Tourneur
Guillaume de Colombieres
Le seig. de Bonnebault
Le seig. de Ennebault
Le seig. de Danuillers
Le seig. de Beruile
Le seig. de Creueceur
Le seig. de Breate
Le seig. de Courtray
The Erle of Eureux
Le seig. de Seint Valery
Thomas, Erle d'Aumale
The Erle de Hiesmes;

"With other lords and men of account in great numbers, whose names the author of the Chronicles of Normandie could not come by (as he himself confesseth;) in consideration whereof, and bicause diuers of these are set forth onlie by their titles of estate, and not by their surnames, we have thought it conuenient to make you partakers of the roll which some time belonged to Battell Abbeie, containing also (as the title thereof importeth) the names of such nobles and gentlemen of marque as came at this time with the Conqueror, whereof diuerse maie be the same persons which in the catalog aboue written are conteined, bearing the names of the places whereof they were possessours and owners, as by the same catalog maie appeare.