MINERALOGY. R89 



fact exhaustive in its treatment of the subject, though not original in 

 matter for the most part. It opens with a catalogue of pajjcrs and books 

 treating of the species pyrargyrite and proustite — extending from 1657 

 to the present time — and then goes on to give a statement of the results 

 reached, chemical and crystallographic. The list of planes observed 

 on the t^YO species is one hundred and eight, with three doubtful ones. 

 To this long list the author considerately makes no new additions. He 

 discusses critically, however, the results of earlier observers, as Haiiy, 

 Mohs, L6vy, and Sella — of whom, for example, Sella added forty-nine new 

 forms — and for conv^enience of reference gives a series of lists arranged ac- 

 cording to zones, according to the numerical value of the indices, by com- 

 binations, and so on. He details also a series of measurements made 

 upon four varieties, all of which were analyzed, and which included a pure 

 proustite (containing no antimony), a pure pyrargyrite (with no arsenic), 

 and also two varieties of the latter mineral, with 2-62 and 3-01 per cent, 

 arsenic, respectively. It appears from these that the fundamental rhom- 

 bohedron becomes a little more acute as the amount of arsenic increases. 

 The values of the vertical axis in the different cases are 0-8034 (proustite), 

 0-7890, 0-7893, 0-78G5 (pure pyrargyrite). A long list of calculated angles 

 completes the memoir. The first part of a somewhat similar monograph 

 has been issued by Sansoni, of Pavia. This is devoted to the calcite of 

 Andreasberg, but when completed the memoir is to cover the whole 

 species. The author has attacked the subject with great vigor, notwith- 

 standing its difficulty and the large amount of the literature devoted to 

 it. His observations are largely original, based upon a collection of 

 twenty-five hundred specimens, loaned from many museums. The 

 number of crystals measured is stated to be seven hundred and twenty- 

 two. Eight types of forms are described and illustrated by a series of 

 figures. The number of planes included is one hundred and thirty one, 

 occurring in three hundred and fifty-nine combinations. 



An interesting contribution to the morphology of the species rhodonite 

 has been made by G. Flink. The specimens examined were from Pajs- 

 berg and L§,ngban, in Sweden, and included a large number of crystals 

 showing considerable variety in habit and occurring planes. The num- 

 ber of the latter identified is twenty-nine, of which nineteen are new. 

 The author follows the suggestion first made in Dana's System of Min- 

 eralogy, and later developed by Groth, and adopts the position which 

 brings the crystals into correspondence with the related monoclinic 

 pyroxene. This relation he discusses at length, and shows that the 

 similarity in forms and angles and cleavage between the triclinic 

 rhodonite and monoclinic pyroxene is very close, to be compared with 

 that between the monoclinic and triclinic feldspars. The axial relations 



are: 



a : b : c a /? , y 



Rhodonite 1-0727 : 1 : 0-62104 70° 4'2' 710 16' 81° 39' 



Pyroxene 1-0903 : 1 : 0-5893 90 74 11 90 



H. Mis. 15 44 



