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the Rev. J. Stephens, M.A. ■who says, that “ in the month ofAugust, 1751, the air having been for some time remark-ably hot and dry, was changed of a sudden by a heavy fallof rain and aS.E. wind. The cliffs near Charmouth, in thewest of Dorsetshire , presently after this alteration of theatmosphere, began to smoke, and soon after they burned witha visible subtle blue flame, for several days successively, andcontinued to smoke, and sometimes burn, till the approachof winter; nay, ever since that time, especially after anygreat fall of rain, thunder, or lightning, or a high S.W. wind,which drives the sea with great violence against the cliffsand breaks off pieces of them, the cliffs continue to smokeand sometimes to hum with a visible flame, which duringthe summer months is frequently observed in the night-time. On examining these cliffs in the year 1759, I dis-covered a large quantity of pyrites, not in regular strata,but interspersed in large masses through the earth, andwhich proved to be martial; of cornu ammonis of dif-ferent sizes, and other shells of a bivalve class, which werecovered over, and mineralized as it were with pyritical mat-ter ; of belemnites, also incrusted over with the like sub-stance; and the cliffs for near two miles long, and from thesurface to thirty or forty feet deep, even to the rocks athigh water mark, with one bed of dark-coloured loam,strongly charged with bitumen. Moreover, I found also adark coloured substance resembling coal-cinder ; some ofthem being powdered and washed in distilled rain-water,and evaporating it to a pellicle, it shot salts into finecrystals, and appeared to be no more than martial vitriol;one ounce of this cinder-like substance yielding one drachmof salt. I gathered up about one hundred pounds weightof the different kinds of these pyrites, marcasites, &c. whichwere laid in a heap and exposed to the air, and every daysprinkled with water; the consequence was, that in aboutten days time they grew hot, and soon after caught tire,burned for several hours, and fell into dust.’’
The following curious optical fact is subjoined to illustrateOptics , (see that article.)
“ When the cliffs were observed to burn in the night-time,the flames were plainly perceived by a spectator at a dis-tance ; but when he drew near to the place seemingly onfire, he could perceive a smoke, but no flame. In the day-time nothing but a smoke was perceived, except the sunshined, when the cliffs appeared, at a distance, as if theywere covered with pieces of glass, which reflected the sun’smeridian rays; but upon drawing near to the place where