Prof.*MaskeIyne and Dr. Lang's Mineralogical Notes, 41 



rlOO, .?l22, fllOl, 5211, o942, a>467. 

 Found. 



rz = 106° 20 



rr' = 87 15 



ra! = 



rc" = 47 15 



r J" = 



16 27 



Calculated, 



106° 



20 



36 



50 



87 56 



46 



7 



47 10 



66 25 



16 



10 



101 



16 



23 



58 



13 



6 



27 23 



53 



34 



42 50 



ob = 13 



or = 



The crystals (PI. II. fig. l)"are perhaps those from Huel Unity. 

 On a specimen from Huel Damsel, given me by Mr. Williams, 

 I found the form in fig. 2 ; and specimens from that locality (so 

 far as it was possible to assign particular labels to the specimens) 

 seemed more slender and fibrous, in one case even asbestiform. 



Examined under the microscope by polarized light, the plane 

 of polarization was found to be parallel to the axis of the prism, 

 and the crystal proved to be devoid of dichroism. 



2. On a Crystal of Colwnbite from Monte Video, Bij 

 N. S. Maskelyne. 



Some time since, W. Garrow Lettsom, Esq., Her Majesty's 

 Minister and Consul-General at the Republic of Uruguay, sent 

 to the British Museum a crystal of Columbite. It was found 

 by him imbedded in granite in the neighbourhood of Monte 

 Video. Mr. Lettsom's quick and accurate eye and intimate 

 knowledge of minerals enabled him at once to recognize the true 

 character of this crystal, and he extracted it from the rock con- 

 taining it. Though split in the operation, the fragments, re- 

 united, build up the entire crystal. He has searched persist- 

 ently for others, but has not found one. 



It is a small lustrous crystal with a very dark brown streak, 

 and with a specific gravity of 5*660. 



It presents the planes (see PI. II. fig. 3) — 



a 100 g 110 u 111 

 b 010 m 130 n 211 

 c 001 # 150 



I take the parameters of this mineral as assumed by Schrauf 

 (Sitzungsberichte der K. AJcad. der Wissenschaften. Wien, 1861, 



