1883.] Crystallography of Miargyrite. 367 



most careful search for it has been so far fruitless. Its habit is 

 like that of the crystal (No. 7) measured by me, but it had certain 

 planes not conspicuous on the latter crystal. I have reproduced his 

 drawing (Fig. 14) as nearly as possible. In Fig. 15 I have repeated 

 this drawing as it is seen through the paper with the plane (100) 

 placed in the vertical. The crystal was probably a fragment and 

 only showed the faces given, which correspond with the faces beloiv 

 the paper in the stereographic projection, as is also the case with 

 crystal 7. Miller partially measured a second crystal belonging to 

 Brooke which I have denoted by D in the tables. The solution 

 seems not to have been completed ; and the diagram accompanying 

 the observations is too rough to render the identification of the 

 crystal easy, but it seems to be similar to crystal 3. As far as 

 shown it was a combination of r]dstwxj3zk. The measurements 

 of tco = 16° 14' and cox = 9° 4' are underlined as if they were from 

 good observations. The zone [/&rfj is also measured. 



Whilst my manuscript was in the press I obtained from 

 Mrs Miller a number of loose papers which contain additional 

 measurements by Prof. Miller. These papers contain the complete 

 solutions of two crystals, A and B. J. is a crystal with well- 

 developed x and g planes. It does not however correspond with 

 any of the crystals named by me, though its habit is much that of 

 No. 14. The crystal B is clearly identical with my No. 7, and 

 Miller's measurements agree closely with mine. Another loose 

 sheet contains a diagram, labelled G, identical with that in the 

 note-book. The crystal-faces were denoted by Greek letters during 

 measurement, and these letters were afterwards replaced in ink by 

 the letters employed to denote the faces in Miller's Mineralogy. 

 The crystals are all similarly placed in the diagrams, so that, as 

 already stated, the faces shown are those below the paper in the 

 stereographic projection. The zone of symmetry was measured on 

 A, but the angles seem to be very unreliable, as the readings are 

 in several cases enclosed between four or five brackets, and I have 

 come to the conclusion that Prof. Miller was in the habit of de- 

 noting unreliable readings by enclosing them in brackets, and that 

 the number of brackets denoted the degree of unreliability. This 

 zone was not measured on B ; the readings for s, t, <w, x are under- 

 lined, and the measurements are identical with those made by me. 

 These measurements have been omitted in my tables ; but all the 

 other important angles given by Miller are appended under the 

 headings A, B, G, which refer to the three crystals so labelled. 

 Miller also measured two or three other crystals, but the solution 

 is in no case completed. Amongst these No. 9 was recognised both 

 by the diagram and by the identity of the angles with those ob- 

 tained by me. Miller seems, however, to have been somewhat 

 puzzled by the plane i on this crystal, and not to have measured 



