DURHAM AND NORTHUMBERLAND. 1Q3

Bishing ratio, as far as thirty parts of air to oneof gas.

Dr. Thomson and Dr. Henry had previouslyexperimented upon the fire-damp of mines;but it does not appear from Sir HumphryDavy’s paper, that its combustible principleshad been analysed comparatively with othergases. The above proportion was however, no• doubt, well known to them, and we have abrief statement of similar facts in Dr. Clanny’spaper to the Royal Society. Sir H. Davy,in his analysis of some gas from the Hepburncolliery, states it to contain one-fifteenth ofatmospheric air, and the most impure to con-tain one-twelfth, which he supposes to bederived from the circumambient air of themine; and one of the fire-damp required twoof oxygen for combustion by the electricspark, forming one measure of carbonic acid.

It is material that the researches of Sir H.Davy corroborate the opinions of former che-mists in regard to this gas, and that it issimilar to the inflammable gas of marshes,which was demonstrated by Mr. Dalton, andfound to consist of four proportions of hy-drogen, in weight 4, and one proportion ofcharcoal in weight 11*3.

An electric spark would not explode five ofo