^80 Scientific Intelligence. 
cal Society in London, which already contains many of the most 
distinguished names in Great Britain. The object of the so- 
ciety is to encourage and promote Astronomy, ‘‘ by collecting, 
reducing, and publishing useful observations and tables; by set- 
ting on foot a minute and systematic examination of the heavens ; 
by circulating notices of all remarkable phenomena about to 
. happen, and of discoveries as they arise ; by proposing prizes for 
the improvement of particular departments, and bestowing me- 
dals or rewards on successful researches in all ; and, finally, by 
acting, as far as possible, in concert with all institutions, both in 
England and abroad, whose objects have any thing in common 
with thejr own, but avoiding all interference with the objects 
and interests of established scientific bodies.’’ 
qPTics. 
7. Harmotome.'-^'Dv Brewster has found, that this crystal has 
Two axes of douhle refraction; and therefore it must have a pri- 
mitive form different from the octohedron with a square base, 
which Haiiy assigns to it. The Count de Bournon had long 
ago, from mineralogical reasons, supposed that Hauy had given 
it a wrong primitive form. 
8. Meionite. — This crystal has been found by Dr Brewster 
to have One axis of double refraction, coincident with the axis 
of the prism. The action of this axis \s Negative^ like that of 
Iceland-crystal. The indices of refraction are, 
Ordinary refraction, 1.6058 
Extraordinary refraction, 1.5763 
9. Petalite. — This interesting mineral, from which is obtain- 
ed the newly discovered alkali called Lithion, has been found 
by Dr Brewster to have a perfect crystalline structure, and to 
possess Two axes of douhle refraction. ^ 
MAGNETISM. 
10. Variation of the Needle at Lyons. — The following mea- 
sures of the variation of the needle were obtained at Lyons. 
1761, Nov. 15“.45'W. 1757, Dec. 17M5' W. 
1762, 16.00 1760, 18.30 
1755, Dec. 16.30 1761, 18.45 
Zach’s Corresp. Astr. i. 223. 
