transparent substance is placed over it. This measurement is obtained by determining with an appropriate scale (to Too of an inch) the distance which the body of the microscope must be moved to bring the original object into focus. When this distance is known, and also the thickness of the object in hand, the index of refraction may be calculated by a simple equation. Mr. Sorby describes the method in full, showing how readily it may be applied and with what useful results. He also discusses some phenomena which were observed in the course of his experiments, and which led to the discovery of "a new class of optical properties." These phenomena are fully explained, in accordance with the known laws of refraction, by Professor Stokes in the Proceedings of the Royal Society, to which it is here only possible to make reference.

Des Cloizeaux has continued his optical examination of the feldspars, and has come to the interesting result that there exists a triclinic potash feldspar, having identically the same composition with the monoclinic potash feldspar- orthoclase. The new species is called by him microcline. He shows, moreover, that these two feldspars generally occur crystallized together, the one interpenetrating the other, often in successive parallel bands. The beautiful green feldspar called amazonstone is conspicuous for this associa tion of the two species: it is also true of the chesterlite of Pennsylvania, and specimens from many other localities. On the other hand, the feldspar enclosing ægirite from Magnet Cove, Arkansas, is found to be pure microcline.

Another extended work on the feldspar group has been published by Professor Szabo, of Buda-Pesth, Hungary. His object is to make it possible to distinguish between the different species as they occur in rocks. The method is based upon Bunsen's "Flame-reactions." It consists in part upon the accurate determination of the degree of fusibility, and in part upon the degree of coloration given to the flame, under different conditions, from which the amounts of sodium and potassium are estimated. The system is an ingenious one, and has been most carefully elaborated by the author; but it may be well questioned whether in hands less skilful than his it would yield any valuable results.

The important group of minerals embraced under the gen

eral term of micas has been the object of some profound investigations by Kokscharof and Tschermak. Hitherto it has been customary to regard part of the micas as hexagonal (e. g., biotite) and others as orthorhombic (e. g., muscovite). The conclusion reached by Kokscharof, after the examination of many specimens of the different species, and a very long series of measurements, is that "the species are all monoclinic with an angle of 90° 0' 0"." Tschermak concludes also that all the species belong to the monoclinic system, and assigns to them an angle of obliquity differing by a minute only from 90°. The latter mineralogist has also investigated with great care and minuteness the optical properties of the different species, and finds in them conclusive evidence of the monoclinic character of the crystals. He divides the species into two groups, according as the plane of the optic axis is (1) perpendicular, or (2) parallel, to the plane of symmetry. The first class includes the species muscovite, lepidolite, paragonite, and margarite, and a portion of the biotites to which he gives the name anomite. The second class includes phlogopite, lepidomelane, zinnwaldite, and the larger part of the magnesia-micas, or biotite, to which he gives Breithaupt's old name, meroxene. The second part of Tschermak's paper, including the discussion of the chemical composition of the species, has yet to appear, and will be looked for with interest.

Dr. Scharff, of Frankfort, has published another of his valuable crystallogenic memoirs upon calcite. He discusses the interior relation between the different crystalline forms of the species, and deduces from them some conclusions in regard to the genetic origin of the crystals.

Of other important memoirs may be mentioned that of Schrauf upon the crystallography of brookite and of lanarkite; by Vom Rath, upon the crystalline form of gold, upon rutile, etc.; of Strüver, upon the minerals of Latium.

AMERICAN RESEARCHES.

A considerable number of new minerals, described by American mineralogists, are included in the following list. In addition to them, many other papers of more or less importance have been published.

The rare minerals of the tantalite and columbite group, spoken of in a former issue of the Record as having been

discovered in North Carolina, have been the object of several researches. Dr. Smith has published an extended paper upon this subject. He describes and gives analyses of the columbite from Mitchell County, N. C., and also that associated with the Colorado amazonstone; of the samarskite of the same locality (first analyzed by Miss Ellen H. Swallow); of a mineral he calls euxenite. He also makes two new minerals, hatchettolite and rogersite, mentioned below. He, moreover, describes the fergusonite from the granite of Rockport, Mass.

Professor O. D. Allen has also published analyses of the samarskite and hatchettolite, which serve to fix their chemical character, as he gives the first determination of the amount of tantalic acid in each. Professor Delafontaine has investigated the samarskite, and announces that he finds. in it about 25 per cent. of tantalic acid, a small percentage of thorium and didymium, also a little erbia, and more of the earth called by him terbia.

In connection with the above minerals, it is interesting to note the discovery, by Professor Eugene A. Smith, of the mineral tantalite in Alabama; and, by Professor W. C. Kerr, of several uranium minerals at the samarskite localities in Mitchell County, N. C. These are uranium mica, gummite, and uraconite (uranium ochre). Further than this, another new columbite, sipylite, is mentioned in the list beyond as having been described by Professor Mallet from the allanite locality in Virginia.

Dr. F. A. Genth has published another memoir upon American tellurium and vanadium minerals. He describes several new species-coloradoite, magnolite, ferro-tellurite (mentioned below)—and also describes the occurrence of native tellurium, tellurite, hessite, and calaverite from several new localities in Colorado. He mentions, too, the discovery of a green mineral, allied to the vanadium silicate roscoelite, from the Magnolia District, Col.

The same author, in the second "Report of the Mineralogy of Pennsylvania," publishes an analysis of the feldspar called cassinite, by Dr. Lea, showing that it contains 3.7 per cent. of baryta. This point is of special interest, as Des Cloizeaux has also recently mentioned the occurrence of a feldspar containing 7.3 per cent. of the same earth.

Professor B. Silliman has described an interesting and rare occurrence of gold interspersed in massive scheelite from Charity Mine, Warren's, Idaho Territory; and also another similar case from the Golden Queen Mine, Lake County, Col., where the gold appears in minute crystalline granules in the scheelite.

Mr. Samuel L. Penfield has given an analysis of the triphylite from Grafton, N. H., which serves to establish the correct formula of the mineral.

Professor A. H. Chester has shown that the so-called peganite of Arkansas is identical with the mineral called variscite by Breithaupt, and callainite by Damour. He has also described a remarkable fibrous variety of sepiolite from Utah, some of which is colored bright green by oxide of copper.

Dr. Koenig has described the occurrence of the rare minerals astrophyllite and arfvedsonite from El Paso County, Col., and has given analyses of both, as also of the zircon associated with them. He has also identified the new mineral strengite (see beyond) at Rockbridge, Va., and has published the results of a crystallographical and chemical examination of it. He has also given the name protovermiculite (see beyond) to a hydrated mica.

Professor G. C. Broadhead has described remarkable crystals of barite from the Last Chance Mine, Morgan County, Mo., and also the occurrence of göthite in limestone concretions from Adair County, Mo.

Garnets of the variety melanite have been found associated in an interesting way with magnetite, apatite, and altered pyroxene on the surfaces of the columnar trap of East Rock, New Haven, Conn.; and also the variety of garnet called topazolite, having a complex crystalline form, at the junction of the trap and sandstone of Mill Rock, New Haven.

Professor H. Carrington Bolton has made an extended examination of the effect of organic acids upon a large number of different minerals. The results are varied and interesting, and suggestions are made from them in regard to the application of some of the acids in the determination of minerals. Mr. J. H. Caswell has added to Professor Bolton's paper a description of the microscopic crystals produced in some of the reactions.

NEW MINERAL SPECIES.

The following is a list of the species recently introduced as new into mineralogy. They are arranged, for convenience of reference, in alphabetical order:

Aglaite.-A hydrous silicate from Chesterfield, Mass.; described by Julien. Related to pihlite (cymatolite of Shepard). Amesite.-Described by Professor Shepard as occurring with diaspore at Chester, Mass. It is found in hexagonal plates and in foliated masses, having the color and lustre of some green talc. An analysis by M. Pisani, of Paris, shows the mineral to be a hydrous silicate of iron, aluminum, and magnesium. It is remarkable for the low percentage of silica (22 per cent.).

Anomite.-A name given by Tschermak to a portion of the biotite micas, particularly those of Lake Baikal, in the Ural. They are distinguished optically, as explained above, from the others which he embraces under the name of me

roxene.

Arsenargentite.-According to Hannay, an arsenide of silver (AgAs). It occurs in orthorhombic crystals, of acicular form, in a mass of metallic arsenic, associated also with some rose quartz. Locality uncertain-perhaps Freiberg.

Bismutosphærite.-A carbonate of bismuth found at Neustädtel, near Schneeberg, Saxony. It appears in spherical and hemispherical forms with concentric structure. The color varies from yellow to brown and black. The specific gravity is high-viz., 7.3. According to Weisbach, who describes the species, it is identical with the original "arsenical bismuth" of Werner.

Bowlingite.-A problematical species from Bowling, on the Clyde, in Scotland. It is probably a decomposition product of the mineral chrysolite. It has a deep-green color, is semi-transparent, and has the hardness and feel of steatite. An analysis of the mineral by Hannay, and another by Young, give very different results, so that no dependence can be placed upon the species.

Bunsenine; Krennerite.-A telluride of gold from Nagyag, in Transylvania, has been called "Bunsenin" by KrenAs the name Bunsenite has already been given to another mineral, Vom Rath has proposed to call the new

ner.