138 Dr Brewster on some New Species of Lead~Ore 
means the case, with regard to the dip and intensity, the propo- 
sition is favourable to Mr Hansteen’s opinion of the earth having 
two axes. 
( To he continued.) 
Art. XXIV. — Notice respecting some New Species (f Lead-ore 
from Wanlockhead and Lead Hills. By David Brewster, 
LL. D. F. R. S. Lond. & Ed. &c. 
In the month of February 1820, Mr Laing Meason, to whose 
kindness I had been indebted for various specimens of lead-ores 
for the purpose of optical analysis, sent me some crystalline frag- 
ments of a yellowish-green substance from Wanlockhead. I 
had found that the Carbonate had two axes of double refraction, 
the principal one of which was parallel to the longer side of the 
rectangular base of its primitive octohedron. The character of 
this axis was negative^ and the inclination of the resultant axes 
was about 9° 40'. The Sulphate of lead had its resultant axes 
inclined at a much greater angle; and the Phosphate and ilfo- 
lyhdate had only one axis of double refraction. 
Upon submitting the substance from Wanlockhead to the same 
examination, I found that it had two axes of double refraction 
like the carbonate ; that the principal axis had a Negative cha-^ 
racter, and coincided with the axis of its primitive form ; and 
that the inclination of its resultant axes was a little greater than 
that of carbonate of lead. These results proved incontestibly 
that the crystal was neither the sulphate.^ the phosphate^ nor the 
molybdate of lead, and rendered it probable that it was not the 
carbonate. In comparing it with this last mineral, I found that 
it was easily scratched by the carbonate ; that it had a laminated 
structure ; and that the laminae could be easily separated from 
one another by the point of a lancet. When the carbonate was 
thrown into dilute nitric acid, it effervesced with great violence: 
crystals of nitrate of lead were speedily formed ; and the carbo- 
nate entirely disappeared. When the new substance was treat- 
ed in a similar manner, it effervesced with very much less vio- 
lence, and left a beautiful white powder, which did not yield 
