278 Mr. Brooke on the Intersection of Crystalline Minei-als, 



a copper or iron wire it was made active, then there was pass- 

 age for the current, and the needle was strongly deflected. 

 From this it appears that when iron is in the peculiar state it 

 is incapable of conducting a current of voltaic electricity. I 

 have one more remark to make, which is, when the iron wire 

 was inactive it was found impossible to make either end of the 

 connecting wire so ; and if the platina was removed from its 

 cup and a common wire put in its place, it always made the 

 wire in the other cup active. 



I forbear to make any observations on the cause of these 

 remarkable phaenomena, as the matter is already in such able 

 hands that it would be presumptuous for me to attempt to ofl'er 

 an opinion ; trusting, however, that what 1 have noticed may 

 be the means of inciting further researches, 



I am, Gentlemen, yours, &c., 



Shawford, near Bath, March 14, 1837- Henry Minch.IN Noad. 



LVI. On the Intersection of Crystals belonging to different 

 Minerals in a regular and constant manner. By H. J. 

 Brooke, Esq., RR.S., Src,^ 



ON examining lately some specimens of Chabasie from Ire- 

 land, I have observed several crystals penetrated by cry- 

 stals of Gmelinite, with their axes in all instances parallel 

 to those of the rhomboids of Chabasie, and the planes also 

 corresponding in position with those of the Chabasie, as shown 

 in the annexed figure. Sometimes the face of the Chabasie is 

 covered by a single crystal of Gmelinite, and sometimes it is 

 studded with many small ones. 



The inclination of the plane P of Chabasie on the axis is 

 38° 34<', and that of plane g of 

 Gmelinite 50°, whence the incli- 

 nation ofg on P is 11° 26'. This 

 position is constant in all the cry- 

 stals I have seen. 



I am not aware of any analo- 

 gous fact having been before no- 

 ticed, and on looking over my 

 own minerals, I observe only 

 two other instances of the same 

 kind. 



One is the combination of Oligiste iron and Rutile. If 

 we suppose a summit of a rhomboid of Oligiste iron replaced 

 by a triangular plane at right angles to the axis, and crystals 



• Communicated by the Author. 



