1822.] Scientific Intelligence. 935 
«‘ When scratched with a knife, the streak is greyish. 
« The colour of the powder is a light-green. 
«< Before the blowpipe, it melts readily into a dark-coloured globule. 
« It displays no electric signs, either naturally or by heat or friction. 
“It is not magnetic, either in the common way, or by the ingenious 
method of double magnetism, which we owe to Abbé Haiiy. 
“ The acids do not act upon it when cold. When digested a long 
time with boiling nitro-muriatic acid, about 1-10th is dissolved. The 
residue is of a lighter colour.” 
The analysis was performed by Mr. Keating, who found it to con- 
sist of 
Smee Oe aa OF IRA WLI 560 
Hermes SAU re ito: ver, VO Sa Te 151 
Protoxide of manganese......... ~"93°5 
PELORIGS OIL poet ote a. 10:0 
xe Ot MNCs er ee sete lacs ate e = 1:0 
Aalermmine,’: LS Dia ee eh eee 2:0 
Loss by calcination.............. 1:0 
TGGsseee sf SS A aie se eg A Dae! ee 
100-0 
The following remarks are added by Mr. Keating: 
“The jeffersonite presents some points of resemblance with the 
pyroxene of Haiiy, but still it can be well distinguished from it. Its 
cleavages are essentially different from those of the pyroxene, but 
appear to approach some of the faces of crystais of substances which 
have been united to this species; for instance, the angles in the diop- 
side (mussite and alalite), fassaite, and in the pyroxene analogique, 
come very near some of the angles of cleavage obtained in the jeffer- 
-sonite. I at first indulged the idea that these cleavages might be con- 
sidered as cleavages parallel to the faces of secondary crystals of 
pyroxene, but upon reflection I am fully convinced that this is not the 
case; for the angles which we have measured cannot be deduced from 
the others by a strict mathematical calculation, and though they may 
approximate, they are notthe same. Besides, no analogy can warrant 
us in admitting, that the regular cleavages of one substance can disap- 
pear entirely, and be replaced by cleavages parallel to secondary crys- 
tals. On the contrary, wherever minerals have been found presenting 
different orders of cleavage, the first or those parallel to the primitive 
form were always predominant. Thus in carbonate of lime, it is not 
uncommon to meet the cleavage parallel to the eguare, but I believe in 
every instance the pri:itive is predominant. In a rarer and more inte- 
resting instance, that of fluor spar, Prof. Mohs has described, and I 
have seen in his possession in Freyberg, specimens of the Saxon fluor 
which cleaved in the direction of the cube and the dodecahedron, but 
the octahedral cleavage was very distinct. Before we change our 
opinion on this point, we must change all our ideas of cleavage, and of 
its high importance in the determination of minerals. - 
‘‘ In the hardness there is also a remarkable difference, the pyroxene 
being decidedly harder. The specific gravity is likewise different: 
the highest specific gravity of pyroxene recorded by Haiiy is that ofa 
large crystal from Vesuvius, which gave 3'3578. ‘Ihe highest specific 
