Miscellanies, 199 



Bergraeister Schnlze, of Dnren, in an excursion in the Eifel, a re- 

 gion of graywacke and basalt, observed from the top of the Niirburg 

 mountain, (a basaltic cone two thousand Prussian feet above the level 

 of the Rhine) on an elevation in an eastern direction, something re- 

 sembling the ruins of a building. Instead of ruins, however, he found 

 it to be two small rocks, about three feet distant from each other in 

 their diagonals, about six feet high, with bases not far from three feet 

 square : one of them was six feet long and three feet broad ; the other 

 was a little shorter, but broader. Both rocks were stratified, with a 

 dip of twelve hours and parallel to the basaltic range on which they 

 reposed. On presenting a magnetic needle to them, it was subject to 

 sudden and violent changes. The circumference of one of them at- 

 tracted the north pole through half its extent, but repelled it for the re- 

 mainder. The manner in which the needle was affected by the other 

 rock may be understood by drawing a line lengthwise through the cen- 

 ter of the upper plane of the rock, and another crosswise through the 

 same plane, so that the point of contact shall occupy the center of the 

 plane : the north pole of the needle was attracted at the extremities 

 of the longer line, while the opposite pole was attracted at the extrem- 

 ities of the shorter one. 



M. Reuss, of Berlin, counsellor of mines, observed the same pro- 

 perty in a mountain of dai'k, grayish, black basalt, free from magnetic 

 iron stone, in the Mittelgeberg, (lordship of Schrochenstein.) The 

 mountain, one thousand eight hundred feet high, is covered with wood 

 to its summit, and precipitous on all sides. Its polarity is so great, 

 that the needle at its eastern foot was moved 40°, and at the summit 

 itself, 90° W. At the Avestern foot of the rock, the contrary was the 

 fact ; but the polarity is shown not only in the whole mass of the 

 rock, but likewise in the larger detached pieces, and even in the small- 

 est fragments ; — the north point of the needle being at one end distinct- 

 ly attracted, and at the opposite end as distinctly repelled. 



These observations, detailed in the Jahrhuch der Chem. u. Phys. of 

 Dr. Schweigger, render it possible that the magnetic results obtained 

 by Prof. Hitchcock upon the mica-slate mountain of Canaan, in Con- 

 necticut, inay be connected with the polarity of rocks ; and not de- 

 pendent upon a mass of native iron, as supposed.* 



5. Nitrous Atmosphere of TirJioot. — Tirhoot is one of the principal 

 districts in India for the manufacture of saltpetre ; the soil is every 

 where abundantly impregnated with this substance, and it floats in the 

 atmosphere in such quantities, that, during the rains and cold weather, 

 it is attracted from thence by the lime on the damp walls of houses, and 



* See Vol. XIV, p. 223, of this Journal. 



