On Columhiie. ■ 151 



nexed description of the crystal according to Naumann's system of 

 notation : 



A comparison of the above angles, leaves no doubt that this crys- 

 tal is a specimen of the species Columbite : and we may extend this 

 remark to all the specimens from the same locality ; for perfect crys- 

 tals, affording the same angles, are of frequent occurrence. The 

 crystal figured by Dr. Thomson is so very irregular, that it cannot 

 be considered an exception to this remark. It presents but one re- 

 placed lateral edge, and one replaced angle, which sufficiently indi- 

 cate that litde or no reliance can be placed upon its apparent form. 

 According to Dr. Thomson's measurement, M : T (mean of 5 tri- 

 als) = 84° 20', T : e (plane replacing the acute lateral edge) = 152°, 

 M : e = 110° 20', a : e (inclination of the plane on the angle, to the 

 adjacent lateral edge) = 143° 45'. The last inclination nearly coin- 

 cides with the interfacial angle a : e as above given. This close ap- 

 proximation would authorize a suspicion of the identity of the crystal 

 examined by Dr. Thomson, with the more regular and highly finished 

 individuals so frequently afforded by the locality. The crystals from 

 Middletown, though often minute, occur occasionally of a gigantic 

 size. Prof. Johnston, of the Wesleyan University, has lately de- 

 scribed a fractured crystal which originally weighed 14 lbs.* His 

 description is accompanied with a figure of the larger fragment into 

 which it was broken. Its weight was 6 lbs. 12 oz. avoirdupois, and 

 in length and breadth it exceeded seven inches. Its general form 

 was similar to the above figures, and it presented the faces Mj M, e, 

 e, e, e, and another imperfect plane, which appears to be o'. 



From the identity in the crystallization, therefore, of the Middle- 

 town and Bodenmais specimens, we are compelled to assent to their 

 continued union in the same species. Slight discrepancies in the 

 physical characters, if they actually exist, should not influence the 



* See this Journal, xxx. 387. The Columbite at Middletown occurs irregularly 

 disseminated in a coarse granite, containing mica and feldspar in large crystalline 

 masses. This feldspar has been quarried for the manufacture of porcelain, and 

 by this means the fine specimens of Columbite which the locality has arfforded, 

 have been disclosed. Albite and small quantities of uranite, rutile and apatite are 

 associated with the Columbite. 



