236 Reports and Proceedings — Mineralogical Society. 



II. — Mineralogical Society, March 22. — Professor H. A. Miers, 

 F.E.S., Vice-President, in the Chair. The following papers were 

 read : — Irregularly developed crystals of zircon (specific gravity 4"0) 

 from Ceylon : L. J. Spencer. The crystals were sent recently by 

 Mr. A. K. Cooraaraswamy to the British Museum for determination, 

 and at first were thought to be rutile. They are of a dark-brown 

 colour and almost opaque ; the specific gravity is 4-09, and is 

 unaltered by heating. A section cut perpendicular to the principal 

 axis shows intei-esting variations in the optical characters, successive 

 portions being isotropic, uniaxial, and biaxial ; the mean refractive 

 index is about 2-0. After being heated to redness and cooled, the 

 material is bright-green in colour, and a crystal section is now 

 entirely biaxial, although the interference figures and birefringence 

 vary in difi'ei'ent parts. — Notes on ' Feather Ore,' identity of 

 ' domingite ' (= ' warrenite ') with jamesonite : L. J. Spencer. 

 ' Feather-ore ' is usually considered to be a variety of jamesonite ; 

 but, since the latter has a good cleavage perpendicular to the 

 length of the fibres, only brittle ' feather-ore ' can be included in 

 Ibis species ; on the other hand, ' feather-ore' the fibres of which are 

 flexible may be either stibnite, zinckenite, plumosite (2 Pb S, Sbo S3), 

 bonlangerite, or meneghinite. ' Warrenite ' is a brittle ' feather- 

 ore,' and further has the same chemical formula (3 Pb S, 2 Sbg S3) as 

 that originally given for the cleavable Cornish jamesonite. — Note 

 on the indices of refraction of antimonite : A. Hutchinson. A prism 

 of refracting angle 8° 51' was found sufficiently transparent to 

 red light for the refractive indices to be determined in the usual 

 way. The results obtained are 4-129 and 3'S73 for rays vibrating 

 parallel to the axes of z and x respectively. Measurements of the 

 <leviation of the ultra-red rays indicate high dispersion in this 

 region of the spectrum. The investigation is being continued. 

 The connection between the atom arrangements of the crystals of 

 certain allied carbon compounds : W. Barlow. Using balls of the 

 same relative size as employed in his previous work, for instance 

 in models of calcite, the author forms a carboxyl slab. By uniting 

 such slabs with balls representing barium, a structure is obtained 

 wliich has the symmetry of barium formate. Again, by uniting 

 the slabs with balls representing hydrogen, a structure with the 

 symmetry of oxalic acid is formed. The author showed that in 

 certain cases, in order to effect close packing, a relative shift was 

 necessary between successive layers. He also briefly discussed the 

 tartaric acids. — On the construction and use of the moriogram : 

 G. F. Herbert Smith, The moriogram is a diagram devised by the 

 author for the graphical determination of the angles between tautozonal 

 poles, obeying the law of rational indices. — Note relative to the 

 history of the Caperr meteorite : L. Fletcher, F.R.S. — On the 

 meteoric irons of Bethany, Lion Eiver, Springbok River, and Great 

 Fish River, South Africa: L. Fletcher, F.E.S.— Professor J. W. 

 Judd, F.R.S., exhibited two Gardette twins of quartz. 



