MINERALOGY, 451 



minations of the elements by Haidiiiger (1824) and Schroder (1855) have 

 been accepted as deserving much confidence. Vrba has had the advan- 

 tages of a larger supply of material and better instrument, and his 

 measurements are exceptionally precise; it is interesting, however, as 

 showing the constancy of the species to note that the axes which he 

 finally accepts are almost identical with those of Schroder and differ 

 very little from those of Haidinger. Yrba adds a large number of new 

 forms, and discusses the crystals from different localities minutely as to 

 occurring planes and angles. The memoir is accompanied by ten plates, 

 giving a spherical projection for the species, and a large number (49) of 

 excellent figures. 



Pyroxene and the allied species have been the subjects of several val- 

 uable memoirs. One of these is by Flink on several of the Swedish min- 

 erals of this group, including a number of varieties of diopside from 

 Nordmark, also schefferite and rhodonite from Lilugbau and Pajsberg. 

 These papers are all published together in Groth's Zeitschrift; some 

 of them api)eared in the Transactions of the Swedish Academy for 

 1885 — the paper on rhodonite was noticed in the Report for 1885. The 

 memoir as a whole is admirably complete, giving not only a descrip- 

 tion of crystalline form with exact measurements, but also a deter- 

 mination of the o])tical characters, and, not less important the chemical 

 composition, since it has been shown that in this group the optical 

 constants and composition vary together. La Valle has published an 

 extended memoir on the Ala diopside, illustrated by numerous figures, 

 and giving some valuable additions to our knowleilge of the form of tlie 

 pyroxene from that famous locality. The same author has earlier (18S4) 

 given an account of the polysynthetic twins of diopside from Ala. 

 Another paper by Gotz gives the results of a study of crystals of diop- 

 side from several localities, showing a number of new forms. The paper 

 closes with a convenient list of all observed planes with the author- 

 ities. The author wisely decides against accepting the new position 

 for the species suggested b^^ Tscliermak, which, though it brings out 

 the relation to the orthorhombic members of the group somewhat more 

 clearl3', results in giving the majority of the forms very complicated 

 symbols. Solly has described axinite crystals from Botallack, and in 

 his paper he has given a list of planes and also a long series of angles. 

 The euclase from the Austrian Alps has been described by Kochlin. 

 The inexhaustible subject of calcite has been discussed by several au- 

 thors; an extended memoir is given by Cesaro of crystals from Belgian 

 localities. 



Eichstadt has given a new description of the gadolinite of Hittero, 

 with a new determination of the form, and a number of new planes. 

 The suite of crystals in hand included the best material for the species 

 ever obtained, and the axial elements seem, therefore, to be worthy of 

 more confidence than those of Des Cloizeaux, though not differing very 

 widely from them. The topaz of Durango, Mexico, has proved a fruit- 



