DURHAM AND NORTHUMBERLAND.

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tremely expensive, and yields but a very in-sufficient supply of light.

This instrument has in many cases greatadvantage over the common low or candle, butnone whatever to recommend it in preferenceto the lamps now invented. Its constructionis very simple, consisting of a wheel with azagged periphery which strikes upon commonflint, and thus produces whilst at work a con-tinual luminous circle, varying in brilliance orthe colour of its sparks according to the preva-lence of carburetted hydrogen or carbonic acid.

But if a proper system of ventilation wereonce introduced, all the danger would be re-moved; and although Mr. Buddie considersthe present system as beyond any further im-provement, I have much pleasure in referringmy readers to a most ingenious plan by Lieut.Menzies, published in Thomson’s Annals,p. 283, April, 1816.

Mr. Menzies has taken up the subject on jtsproper ground, and endeavours to facilitatethe purification of the mines by simple andincontrovertible means rather than by the com-plicated agencies now in use. He has consi-dered the inclination of inflammable airs toascend rather than to be compressed ; and hasassimilated this quality with the general dip andrise of the coal strata.