LL. R. Gibbes on the Occultator. 191 
forty-five compounds containing them, it will be seen I have 
not changed at all. His numbers for chlorine, bromine, iodine, 
and sulphur, however, which I have altered the most, were 
obtained from a comparatively small number of compounds 
containing them. 
my alterations be accepted, and also my new determina- 
tions, then the list of the atomic volumes of elements in their 
iquid compounds at their boiling points will stand as follows. 
Hydrogen 5'5, chlorine 22-0, bromine 27°5, iodine 38-5, oxygen 
78 and 122, sulphur 23-4 and 28°6, selenium 23-4, mercury 
15°6, zine 23°4, nitrogen 2°15, 8-6, and 17-2, boron, phosphorus, 
vanadium, and arsenic 25°8, antimony, and possibly also bis- 
muth 34:4, carbon 11-0, silicon, and titanium 33-0, tin, doubt- 
ful, either 41‘5 or 44:0, probably the latter, 
Note—For the benefit of any who may wish to consult the authorities upon the 
Subject of atomic volumes, I will state that, apart from Kopp’s original articles, 
Previously referred to, the bes 8 e been able are in the fol 
lowing works. ‘‘ Watts’ Dictionary,” vol. 1, article “ Atomic Volume.” Kekule's 
‘Le h der Organischen Chemie,” vol. 1, an , Kopp, and Zamminer’s 
hrbue’ 
“Lehrbuch der Physikalischen und Theoretischen Chemie. 
Arr. XIV.—On the Occultator ; by Prof. Lewis R. Grenrs, 
ee Astronomy, &c., in College of Charleston, Charleston, 
In the years 1848-1854, I was much engaged in observing 
Sccultations of fixed stars by the moon, and as a means of ob- 
taining the approximate times of disappearance and reappear- 
ance with less labor than by calculation, I devised and con- 
structed, in 1849 or 1850, an instrument for that purpose, to 
Which I gave no special name, This instrument is still in my 
Possession, but not in use, as certain parts, presently to be men- 
Honed, have deteriorated with the lapse of time. 
. The Rev. Thomas Hill, of Cambridge, Mass., has published 
in the Nov. number of this Journal, a description and figure of 
an instrument for the same purpose, invented by him in 1842, 
and called by him the occultator. As the two instruments 
have the same end in view, there is a general agreement in 
plan, but the details differ. Mine is founded on the well 
Wh method of orthographic projection usually adopted in 
Projecting eclipses and occultations, and I have published no 
‘scription of it, nor do I propose doing so at the present time; 
but I wish to mention now, the devices I adopted to overcome 
certain difficulties which present th | 
