1817.) Royal Society. 231 
Were we to suppose it a compound of two atoms grey oxide, one 
atom ammonia, and two atoms water, its constituents would be 
(reckoning an atom of grey oxide 9°5, an atom of ammonia 2°125, 
and an atom of water 1125) :— 
Grey ONIdGH hi Wide oii dm arin doo ivan SID 
AMMODB ai pelisienideens Acclenwiice ss 9109 
Weaken sida ciatslniate (si obhe crealsictrerncde ED 
100°00 
Now these proportions approach so nearly to those of Mr. Davy, 
that they serve very much to corroborate the accuracy of his ana- 
lysis. ‘The paper was terminated with a theory of the fulminating 
platinum. But as this theory nearly agrees with the previous theory 
of fulminating gold, as given by Bergman and Berthollet, I con- 
sider it as unnecessary to detail it here. ‘The experiments in this 
paper appear to have been carefully made, and bear the stamp of 
precision. 
On Thursday, Feb. 20, a paper by Mr. Pond, the Astronomer ° 
Royal, was read, on the Parallax of the fixed Stars. It is well 
known that Dr. Brinkley has for several years past been observing 
certain fixed stars with a circular instrument at the Dublin Obser- 
vatory; that he has observed a sensible parallax in several of them 
amounting to about 2”, that this parallax has constantly appeared 
in every year’s observations, and that it is too great to be ascribed 
to errors of observation. It was desirable that these observations 
should be confirmed by other astronomers. The circular instrument 
at Greenwich was considered as well adapted for the purpose: ac- 
cordingly Mr. Pond made observations with it in 1812 and 1813; 
but he soon found that it would not answer the expected object, 
unless it could be wholly devoted to such observations. In conse- 
uence, he proposed at the last visitation that two ten-feet telescopes 
tted with micrometers should be fixed to stone pillars, for the 
purpose of observing the parallax of the fixed stars, which proposal 
was approved of. ‘Till these can be erected, two temporary tele- 
scopes have been fixed for making observations. 
The object of the present communication was to state the result 
of the observations made in 1812 and 1813. The stars observed 
were « Aquile, a Lyre, and « Cycni. The amount of the parallax 
did not exceed one-fourth of what Dr. Brinkley had observed; but 
it was constant, like that observed by Dr. Brinkley. Mr. Pond 
suspects that the difference is owing to some other cause than 
arallax ; but he is far from being of opinion that the observations 
which he has already made are sufficient to decide the point. He 
hopes soon to be able to offer a new set of observations on this inte- 
resting subject. 
LINNEAN SOCIETY. 
On Tuesday, Feb, 4, part of a paper by the late G. Anderson, 
Esq. F.L.S, was read, entitled, A Monograph of the Geuus 
Ponia. Linnzus at first confounded all the species of pxonig 
