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The specimens obtained from the edge of the lake are chiefly masses of 

 sulphate of lime, sometimes in the form of massive gypsum, but more frequently 

 crystallized in the form of oblique prisms of selenite. The faces of these 

 crystals are frequently coated with crystalline films of pure sulphur, the forms 

 of which have been examined by Mr. E. H. Davis, who has furnished the 

 accompanying notes on the subject. 



Notes on Crystallized Sulphur from White Island. By E. H. Davis. 



This sulphur presents many points of interest, but especially in respect 

 of its crystalline form. While examining the largest specimen in the Museum, 

 I was struck by the peculiar arrangement exhibited by the crystals when 

 examined with an ordinary pocket lens ; this induced me to examine some 

 more carefully under a microscope, and the result was so very striking that I 

 propose describing the various crystals to the Society. 



Sulphur, as is well known, crystallizes in the trimetric or rhombic system, 

 usually in small pyramids, which are often very perfect ; there are also many 

 complex forms, a full description of which may be found in any Manual of 

 Mineralogy. 



The form most usually affected by the White Island sulphur is the well 

 known sharp acicular crystal, but it also assumes very much more complicated 

 forms, some of which at first sight appear to be quite independent of all 

 I'ules of crystallization. 



No. 1 is a group of prismatic crystals attached to one another by the 

 angles, and not the faces, of the macroprism which forms the apparent length 

 of the crystal, the terminal planes being the faces of the macro-pyramid. The 

 most curious feature about this group is the small crystal formed on the 

 principal axis of the perfect form, on the top of the others ; actually, this 

 small offshoot is the chief of the group, being a normal prism terminated by 

 an obtuse pyramid. 



No. 2 is a regular rhombic pyramid, terminated by the basal pinacoid. 

 This is a very common form, and would not have been worth noticing had I 

 not fortunately thought of trying the effect of a polariscope on the crystal, 

 when I discovered the two small crystals growing from one of the polar edges 

 towards the centre of the crystal in which they were included. I strongly 

 suspect that these were cavities originally filled with aqueous vapour, for with 

 the blue light they were colourless, and with the orange, the same colour as 

 the sulphui", or nearly so. 



No. 3 is an acute j)yramid with the brachydiagonal elongated and converted 

 into the principal axis of a small crystal. 



No. 4 is a most interesting group, two of the crystals being macrodomas 

 terminated by trachydomas, one of the faces of the latter being continued and 



