THE 
MONTHLY MICROSCOPICAL JOURNAL, 
JUNE 1, 1877. 
I.—On the Mineralogical Composition and the Microscopical 
Structure of the Belgian Whetstones. 
By Rev. A. Rénarp, 8.J., F.R.MLS. 
(Read before the Royau Microscopicau Soctety, April 4, 1877.) 
Amone the rocks used as fine whetstones, there are none, I think, 
more justly celebrated in Europe than those found in the neigh- 
bourhood of Viel-Salm, in the province of Liege, Belgium. They 
are in shape parallelopipeds, composed of a stratum more or less 
deeply coloured yellow, and of a stratum coloured blue-violet ; and 
are exported to every country in Europe and the Orient. 
Although I intend to direct attention chiefly to their constitu- 
tion as found from their study under the microscope, and to the 
light which this method of study throws upon the origin of those 
rocks and upon their physico-chemical constitution, yet I shall 
briefly notice some of the interesting geological considerations 
relative to their bearing and to their relations with the adjacent 
strata. 
The hones of the neighbourhood of Viel-Salm are found among 
the rocks which Dumont called Salmien, but which seem to resemble 
very much the English Cambrian, and to be the equivalent of the 
schist of Tremadoc. 
They form veins in the Cambrian slate of from one to two 
centimeters thick, but whose direction is so irregular, and whose 
composing strata are so winding and tortuous, that many geologists 
have mistaken them, and they have been not seldom described as 
real veins; whilst I have shown, supported, moreover, by Baur and 
Dumont, that they are regularly intercalated in the stratification, 
and form real strata in the slate, with which it is intimately united. 
The facts upon which I base my deductions and the macro- 
scopical descriptions, are given at length in a memoir which I 
devoted to this question. 
Before touching upon the microscopical study, let me say a 
word or two on the relations between the whetstone and slate, as 
by that means I may be more readily understood in the description 
of the whetstone as it appears under the microscope. 
When one sees a hone haying one layer of a yellowish white 
VOL. XVII. % 
