MICROSCOPY. 253 



crystals, are garnet of the variety called spessartine, which, 

 in its pure form, is a little transparent crystal of a pale-yel- 

 low color, so that the union of a great number of infinitely 

 small crystals should produce, when regarded ensemble, a yel- 

 lowish-white tint, which is the prevailing color of the whet- 

 stones. Chemical analysis also indicates this manganese gar- 

 net, and near the veins of whetstone MM. De Koninck and 

 Davreux discovered beautiful little garnet crystals of spes- 

 sartine. Another element of the whetstone is schorl, showing 

 under the microscope as minute parallelograms, pale green, 

 blue, or grayish, and dicroscopic; also a prismatic mineral 

 allied to chrysoberyl, and only discernible with high powers. 

 It appears as prisms of a greenish-yellow color, scattered 

 throughout the whetstone sporadically, sometimes ranged 

 in lines, often interlacing and superposed, but maintaining a 

 position the while too regular and constant in its repetition 

 not to be subject to some crystallographic law, the simplest 

 form being geniculated twins, with an angle of 60. The 

 author concludes, from his examination and microscopical 

 study of this rare rock of Salm and the neighborhood, that 

 the whetstone bands are real layers in the Cambrian forma- 

 tion, deposited in the same way as the adjoining slates, and 

 only metamorphosed in a general way, the mineralogical ele- 

 ments being present from the very beginning of the deposit. 



In the July number of the 1 Monthly Microscopical Journal 

 is a graceful tribute to Ehrenberg by T. Rupert Jones, who, 

 though finding it impossible to accept most of Ehrenberg's 

 specific, and even generic, determinations, states that the 

 better his work is elucidated and understood, the more will 

 his beautiful and lasting illustrations and his painstaking 

 synoptical registers advance the progress of biology in re- 

 lation to both the present and the past. 



After a careful comparison of all Ehrenberg's figures of fossil 

 Foraminifera, Professors TV. K. Parker and T. Rupert Jones 

 have stated in the Ann. and Mag. Nat. Hist., series 4, vol. ix., 

 p. 216, etc., that, besides twenty undetermined forms, 138 

 species and noticeable varieties are shown in the "Mikrogeol- 

 ogie," most of which are living at the present day, and eighty- 

 one of which had been named by other observers. Since the 

 publication of the " Mikrogeologie," two noble memoirs have 

 been published by Ehrenberg, the first in 1872, being the 



