Geology and Natural History. 155 



Trenic, Bohemia; Zbiroff, Bohemia ; Weilburg, Baden ; Zwickau, 

 Saxony; Bearville, Lancaster Co.,Penn., and Lobenstein, Russia. 

 In general the crystals were exceedingly minute, and very much 

 extended in the direction of one axis. The largest crystals 

 noticed were from Lobenstein, but even these did not exceed 

 0*04 mm in thickness. They all showed extinction parallel and at 

 right angles to the long axis, and the larger crystals polarized in 

 rather bright colors. The pleochroism was very slight, only 

 being observed in the case of one or two of the largest crystals, 

 when the color was an orange-yellow in the direction of the long 

 axis and a light yellow at right angles to this axis. The average 

 crystals from Zbiroff, were slightly larger than those from the 

 other localities. In general the crystals appeared to be termi- 

 nated by cleavage or pinacoidal planes at right angles to the long 

 axis, although in some cases pencil-pointed terminations were 

 noticed and also oblique and irregular terminations and fractures. 



Two of the largest crystals from Lobenstein, showing termina- 

 tions, were examined with the following results. In one case the 

 terminations resembled pyramid or dome faces with the apex 

 truncated by a pinacoid. Angle between pyramid or dome faces 

 over the vertex = 74° 20'; angle (supplement) between these 

 faces and the long sides of the crystal = 37° 10'. Angle between 

 pinacoid and sides of crystal = 90°. In another case the ter- 

 minations resembled pyramid or dome faces without any pina- 

 coidal truncating plane. Angle between these faces over vertex 

 = 90° (approximately). These measured angles would give an 

 axial ratio of 1 : f . Some of the crystals also appeared to be 

 modified in the direction of the long axis by prism or dome faces. 

 The measurement of these angles was made on the revolving 

 stage of the microscope, using the cross hairs in the eye-piece as 

 reference lines, and the measured crystals were saved by cement- 

 ing them to a glass slide with a very dilute solution of gum 

 damar and benzole. Strengite, in very pretty pink botryoidal 

 forms with drusy surface, was noticed occurring with the cacox- 

 enite on limonite from Noble's mine, Bearville, Lancaster Co., 

 Penn. 



Mineralogical Laboratory, Columbia College. 



6. The Great Barrier Reef of Australia : its Products and 

 Potentialities ; by W. Saville Kent. With a chart, 48 photo- 

 mezzotype plates, 16 chromo plates and many woodcuts. 380 

 pp. 4to. London, 1893 (W. H. Allen & Co. K — This beautiful and 

 interesting volume presents the first results of the work accom- 

 plished by Mr. Saville Kent in his study of the Great Barrier 

 Reef of Australia ; a work which was made possible through the 

 enlightened liberality of the Queensland Government. The more 

 minute and technically scientific descriptions of the different 

 forms of animal life, which the author has studied, are promised 

 in a later publication. The work now completed presents, in a 

 manner equally satisfactory to the scientific and to the general 

 reader, a vivid picture of the marvellously varied and beautiful 



