of two Rocks of Basalt near Niirburg in the Eifel. 175 



rity in the position of the axes either in One and the same mass 

 of rock in general, or a fixed correspondence, in the position 

 of these axes, with the direction of the strata of the rocks. In- 

 dividual cases are indeed found in which a number of traver- 

 sing magnetic axes lie parallel in a rock, and even instances 

 in which their position is in constant correspondence with the 

 direction of the strata of the hills in which they are found ; but 

 there are found in the same rock, besides those parallel axes, 

 others of a deviating position, so much so as to intersect and 

 cross each other, and to meet within the rock with poles of the 

 same description*. 



But very recently I received an official report of the mag- 

 neto-polar property of two basaltic rocks in the Eifel, which 

 may be considered as an extraordinary instance of variety of 

 position of the axes contained in them. On my request to 

 Bergmeister Schulze of Duren to communicate to me his 

 observations on them, I received the following letter from him, 

 which, besides containing the information I sought, gives some 

 other interesting particulars of the district of the Eifel. 



I consider these two basaltic rocks as peculiarly adapted for 

 making strict investigations on the polarity of rocks, as they 

 are comparatively small, and may be examined on every side, 

 and the variations of the phaenomena are placed close, and yet 

 very conspicuously, together. I shall employ my first leisure 

 for their examination. For the present, a young but distin- 

 guished natural philosopher has promised to devote a few 

 days to this purpose during the Easter vacations. If the re- 

 sults turn out generally interesting, I shall publish them. In 

 the mean time the following letter may suffice. 



"Duren, 18th February, 1828. 



" Since you, my respected friend, consider the discovery I 

 made during my last summer's excursion in the Eifel of some 

 rocks of basalt having magnetic power, sufficiently important 

 to be placed before the public, I shall have the honour to give 

 you a short account of it. I only regret that it cannot be a 



* The greatest constancy in the position of magnetic axes in polarizing 

 rocks has probably been observed in that of the above-named Haidberg. 

 But it only requires a close study of the observations made by the last ex- 

 aminers of it, Professors Goldfusz and Bischof, to discover that there must 

 be in this- rock also, besides a great number of parallel axes, others of a 

 deviating position ; a fact which beeomes the more apparent if we compare 

 the description of the properties of the whole rock with the experiments 

 made by Prof. Bischof with detached pieces of it. See Beobachtungen 

 uber die magnetischen Eigenschaften einiger Gebirgsarten des Fichtelgebirges, 

 by Dr. G. Bischof, in this (Schweigger's) periodical, old series, vol. xviii. 

 p. 297, &c.) Compare also in particular the account accompanying that 

 Essay, and observe that page 324, line 17, the word south-west appears in- 

 stead of south-east ; evidently through an error of writing, or of the press. 



scientific 



