416 Journal of Applied Microscopy. 



In a rock from Ticchiena, Rome, thirteen measurements in the zone [100] gave : 



0, 1, 1, 2, -1, 4, 13, 16, 16, 17, 17, 1.^, 19 degrees. 

 Five are near zero, six are near 18, one is at 18 — that is, it conforms to Labra- 

 dorite A/'^ An^. 



Viola, C. Versuch einer elementaren Feldspathbestimmung in Diinnschliffe nach dem 

 allgemeinen Principe der Wahrscheinlickkeit. Zeit. f. Kryst. 30: 36-54, 1898. 



Florence, W. Daistellung mikroskopischer After describing a method for deter- 

 Krvstalle in Lothrohrperlen. Neues Jahrb. . . ,, , , , , .,. , , 



f. Min. 1898, 2: 102 146. mmmg the degree of solubihty (not the 



ease) by using a bead made on a loop 



of 2.5 mm. diameter, with wire ti.o mm. thick, and dissolving therein weighed or 



measured amounts of substance up to the saturation point, the author describes 



at length and illustrates with twenty-six photo-prints the method of obtaining 



crystals in blow-pipe beads. 



The fluxes chosen are (KNa)._, B^O^, the borate of potassium and sodium, 

 and Na PO, or salt of phosphorus. An almost spherical bead is made in a cir- 

 cular loop mm. diameter, and this is nearly saturated by lead oxide, PbO, thus 

 lowering the melting point and getting rid of disposable boracic or phosphoric 

 acid. After this the substance is added in fine powder up to the point at which 

 continued cloudiness indicates separation. The lead oxide assists by lessening the 

 number of crystals formed, and also by lowering the fusion point so that the bead 

 may be easily kept liquid and the incipient crystals given a chance to come 

 together. 



The hot bead is then pressed flat between two thick glasses and examined 

 with the microscope. 



The results are given for twenty-three oxides and twenty-four minerals ; the 

 resulting crystals and their optical behavior are described, as well as the bead 

 colorations. a. j. m. 



Daly, Reginald A. A comparative study of It is now well recognized that the little 

 Etch-Figures. The Amphiboles and Py- , .. . 111 



roxenesf Proc. Amer. Acad. Arts and Sci. angular cavities or pits produced by 



34: 373-430, March, 1S99. the attack of a liquid or gas upon the 



face of a crystal, are of great assistance 

 to the mineralogist in determining the symmetry of a crystal. The very elabo- 

 rate study of the etch-figures of amphibole made by Mr. Daly was undertaken 

 primarily, however, from a petrographical standpoint in order to find a means of 

 orienting amphibole cleavages in crystalline rocks. It is of interest, also, as an 

 attempt to devise a standard method from which all variables, except that of 

 time, have been eliminated. 



The method, in brief, consists in treating prominent faces, especially those 

 parallel to cleavages, in concentrated commercial water solution of hydrofluoric 

 acid, at the temperature of the water bath, until the figures developed almost 

 overlap. A platinum crucible of about four cm. diameter at the bottom is filled 

 to a depth of about one cm. with the hydrofiuoric acid ; the crystal is suspended 

 in this in a platinum net, and the crucible placed in the water bath. The attack 

 is stopped at any moment by plunging the net into cold water. 



By maintaining these standard conditions it was believed that not only would 



