194 Prof. Kelland on Mr. Earnshaw’s Reply to the 
it to a new analysis. The result was so different from Mr. 
Keating’s, that it became evident that the position which I had 
assigned it was a wrong one, and that in reality it was a qua- 
druple salt consisting of silica united to the four bases, lime, 
alumina, iron, and magnesia. 
The colour of Jeffersonite is dark olive green, passing into 
brown. It is foliated, and according to Keating, may be 
cleaved in various directions. The specimen in my possession 
is an imperfect four-sided prism; but the faces are not smooth 
enough to admit of measurement. 
The lustre is resinous and almost semimetallic; the streak 
is gray, and the powder light green. It is rather harder than 
fluorspar, though softer than apatite. The specific gravity is 
3°51. Before the blowpipe it fuses readily into a dark co- 
loured globule: its constituents are - 
Silikal oe 4h). leew ahd) Gee. 
Taio). Bistio ss) She: tay SRE 
Alina 8 Slag cals SE 
Protoxide of iron... . 12°30 
Mapnesia».>./.) 630.4. .2 18400 
Moistare:( 6 waita ay. ac eid 
99°35 
The constitution may be represented by the formula 
4(Cal S) + 4(Al S) + 2(fS?) + MgS®; 
so that it differs essentially in its composition from both pyr- 
oxene and amphibole. 
XXXI. On Mr. Earnshaw’s Reply to the Defence of the New- 
tonian Law of Molecular Action. By the Rev. P. KELLanp, 
M.A, F.R.SS. L. & E., $c. Professor of Mathematics in 
the University of Edinburgh*, 
ON receiving the Philosophical Magazine for December, 
1842, in which Mr. Earnshaw terminates his Reply tome 
by requesting an answer to four questions, I thought it right not 
to delay complying with his request. But I am not, of course, 
hindered thereby from discussing the rest of his paper. In 
point of fact, I am in arrear two answers to Mr. Earnshaw, viz. 
to part of his paper in the November Number, and to that be- 
fore me. I do not, however, see that the former of these re- 
quires any rejoinder, I admit the first and second remarks in 
it, understood of relative, not of absolute displacements, but do 
not see that they bear on the question before us. To the third 
remark J have already replied. : 
Let me then confine myself to the last paper, and examine 
* Communicated by the Author. 
