nature of flame. This improvement was the addition of a means of giving light in an atmosphere too foul for vivid combustion and the production of flame, by introducing a small cage or spiral of platinum wire just above the wick of the lamp. This had the marvellous effect of occasioning the combination of the inflammable air with oxygen, or its combustion at a temperature only sufficiently high to make the platinum luminous,-not sufficiently high to have this effect on the volatile products of the combustion; or, in other words, produce flame. Thus improved, the miner with the safety lamp might work in any part of the mine where life could be supported, and have the advantage of a steady though feeble light.

"Explanation of the Plate representing different Forms of the Miner's Safety Lamp, and of the Apparatus for giving Light in Explosive Mixtures.

"a represents the single cylinder of wire gauze ; the foldings a a a must be very well doubled, and fastened by wire. If the cylinder be of twilled wire gauze, the wire should be at least of the thickness of one-fortieth of an inch, and of iron or copper, and thirty in the warp, and sixteen or eighteen in the weft. If of plain wire gauze, the wire should not be less than one-sixtieth of an inch in thickness, and from twenty-eight to thirty both warp and woof.

"b represents the second top, which fits upon a. "c represents a cylinder of brass, in which the wire gauze is fastened by a screw to prevent it from being separated from the lamp by any blow. c is fitted into a female screw, which receives the male

screw ẞ of the lamp: f is the lamp furnished with its safe trimmer and safe feeder for oil.

"A is the wire gauze lamp put together with its strong wire supports, which may be three or four receiving the handle.

"g is a small cage made of wire of platinum, of one-seventieth or one-eightieth of an inch in thickness, fastened to a wire for raising it above the wick, for giving light in inflammable media containing too little air to be explosive.

"h is a similar cage for placing in the bottom of the lamp, to prevent it from being smoked by the wick.

"C is a lamp of which the cylinder is copper, of one-fortieth of an inch in thickness, perforated with longitudinal apertures of not more than the onesixteenth of an inch in length, and the one-thirtieth in breadth. In proportion as the copper is thicker, the apertures may be increased in size. This form of a lamp may be proper where such an instrument is only to be occasionally used; but for the general purposes of the collier, wire gauze, from its flexibility and the ease with which new cylinders are introduced, is much superior.

"D is a lamp fitted with a tin plate mirror of half the circumference of the cylinder, and reaching as high as the single top, which may be used in strong currents of fire-damp, to prevent the heat from rising too high.

"All these forms of the wire gauze lamp are equally safe.* In the twilled gauze lamp, less firedamp is burnt, and the radiating and cooling surface

* That is, according to circumstances, as explained, and on the prin ciple distinctly pointed out," that the cylinder should in no case be suffered to be heated above dull redness." Inattention to this, has led to innumerable errors and misstatements, and, it is to be feared, to accidents.

is greater, and it is therefore fitted for very explosive mixtures or for explosive currents. The wire gauze lamp with a double cylinder, or with a reflector, answers the same purpose.

"The general principle is, that the cylinder should in no case be suffered to be heated above dull redness; and this is always effected by increasing the cooling surfaces, or by diminishing the circulation of the air.

"Mr. Newman has applied a lens to the exterior of some of the lamps; which, when a strong light is required to be thrown upon particular objects or parts of the mine, has been found useful."

Some extracts may now be given on the application of the safety lamp, from communications to my brother. They are taken from the third section of his work, prefaced by the remark, that "the evidence of the use of a practical discovery is of most value when furnished by practical men; " and are well adapted to give just ideas of the danger encountered and overcome, and of the simplicity of the means by which it was effected.

Extract from a Letter on the Practical Application of the Wire Gauze Safe Lamp, from John Buddle, Esq. to Sir H. Davy.

"Walls End Colliery, Newcastle, 1st June, 1816. "After having introduced your safety lamp into general use, in all the collieries under my direction, where inflammable air prevails, and after using them daily in every variety of explosive mixture, for upwards of three months, I feel the highest possible gratification in stating to you that they have answered to my entire satisfaction.

"The safety of the lamps is so easily proved by taking them into any part of a mine charged with fire-damp, and all the explosive gradations of that dangerous element are so easily and satisfactorily ascertained by their application, as to strike the minds of the most prejudiced with the strongest conviction of their high utility; and our colliers have adopted them with the greatest eagerness.

"In the practical application of the lamps, scarcely any difficulty has occurred. Those of the ordinary working size, when prepared with common cotton wick and the Greenland whale oil, burn during the colliers' shift or day's work of six hours without requiring to be replenished; and the safety trimmer answers the purpose of cleaning, raising, and lowering the wick completely.

"The only inconvenience experienced arises from the great quantity of dust, produced in some situations by working the coal, closing up the meshes of the wire gauze, and obscuring the light; but the workmen very soon removed this inconvenience by the application of a small brush.

"Our colliers have found it most convenient to hang the stationary lamps from small wooden pedestals; but, on observing that where the side of the lamps have been suffered to come in contact with the pedestals the wood is charred to a considerable depth by the heat of the lamps, I have thought it right to use small iron pedestals instead of the wooden ones.

"Besides the facilities afforded by this invention to the working of coal mines abounding in fire-damp, it has enabled the directors and superintendants to ascertain, with the utmost precision and expedition, both the presence, the quantity, and the correct situation of the gas. Instead of creeping inch by inch