Traps and Bafalts, 43 1 § III. Of Traps and Bafalts. As the various opinions concerning the origin of bafalts form an interefting part of the Minera- logical Hiftory of this Century from the nu- merous refearches they occafioned, and the many difcoveries both of unknown truths and unfuf- pefted errors that thencc refulted, it will not be amifs to flate thefe opinions in the order in which they were offered to the public, before we enter into a particular examination of the merits of each. The circumftance that firft lcd philofophers into a particular enquiry concerning the origin of bafalts, was the difcovery of antient volcanos, now extintt, made by Mr. Guethard, of the Royal Academy of Paris, in the year 1751, and publifhed among the Memoirs of that learned body for the year 175a. Thefe he found in Au vergne i he inferred their antient volcanic ftate from the ftrong refemblance between feveral fof- fils they contained and thofc of Vefuvius j among ' thefe foffils, however, he does not reckon ba- falts; on the contrary, in his Memoires de Phy- fique, publifhed feveral years aftcr, hc afcribes to them a Neptunian origin. In 1763, Mr. Defmarctz, a member of the füme academy, travelling through Auvergne, obferved a multitude of bafaltic pillars on the 3 road