186 Scientific Intelligence. 



Hanover. Second Edition, greatly enlarged. Vol. I. Gottingen, 1828. — 

 This first volume of a very classical and important work contains the in- 

 troductory part of the science, and is divided into two parts. The first 

 treats of the external, physical, and chemical properties of minerals; and 

 the second on the history and method in mineralogy. The succeeding 

 volumes of the work will appear after the return of the author from a tour 

 to London, Paris, and the Pyrenees, in the summer of 1829. 



GEOLOGY. 



19. Account of the Explosion of Slickensides. By White Watson, F. L.S. 

 — Slickensides is a singular formation occurring in some perpendicular mi- 

 neral veins, consisting of two imperceptible specular surfaces, joined together 

 without cohesion ; they are sometimes composed of a mixture of fluor, car- 

 bonate of lime, galena, blende, &c.; at others, these surfaces are thinly spread 

 over with galena, as smooth and shining as if polished by art, and are then 

 termed looking-glass ore : they are sometimes flat, at others waved ; some- 

 times the waves in the same specimen are both perpendicular and horizon- 

 tal ; often in wedge-shaped nodular masses of various sizes, dispersed in 

 the veins. When their edges occur in the face of the vein, on the miner 

 striking his pick into the vein they separate, in some districts without, in 

 others with a slight report; and in some of the mines in the neighbourhood 

 of Eyam, in Derbyshire, with loud reports, particularly in Cracking-hole 

 vein, in Hayclifie title, situated in the shell limestone, beneath the shale 

 stratum, where in the centre of the vein, termed a shack vein, was a small 

 white impalpable (not effervescing) powder, called a mallion, a quarter of 

 an inch thick, which on being scratched, a loud explosion immediately en- 

 sued, before which explosion a singing kind of noise was heard. By setting 

 a blast in the vein at a short distance from the mallion, after the blast was 

 fired, in a few minutes an explosion took place, when a large quantity of the 

 vein fell down. In the year 1790, a loud explosion took place from a slide 

 joint of Slickensides going across, but not into the cheeks of the vein con- 

 taining the mallion, which caused on its being stirred the loudest explosion 

 and the largest quantity of vein materials to come down The vein there 

 was four feet wide, and three hundred yards from a dike vein. The last 

 great explosion was in the year 1 805. It has sometimes happened that 

 persons have been maimed, and even killed by this phenomenon ; which, 

 however, has not been noticed from Slickensides where no shale is incumbent 



Are not these explosions occasioned by combining by friction, carbonic 

 acid gas with the hydrogen gas, which probably descends down a vein from 

 the shale, and which hovers in the roofs of many subjacent caverns, and 

 which instantaneously ignites with a tremendous explosion on the approach 

 of the flame of a candle ; and instances have occurred in which they have 

 proved fatal to human life, 



20. Date of volcanic agency in Auvergne, — There is extant in one of the 

 public libraries at Rome a letter from Sidonius Apollinaris, who was bishop 

 of Clermont in Auvergne in the fifth century, (he was born in 430, and 



I 



