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' Adie Pioining on Occultations by the Moon and Planets. 15 
sted as indications of gaseous cohesion, it may be remarked 
that in both cases the form is doubtless due in great part to the 
composition of the oblique forces of the concurring jets, and 
that the resemblance is perhaps further increased by the resist- 
ance of the air, producing on the air-jet an effect in some degree 
the same as that of the mutual cohesion of the parts in the jet 
of liquid. Indeed if from such analogies of form we are to 
infer the control of cohesive force in streams of air, may we not 
with equal reason, in comparing the eddies and whirlpools of 
water with the dust-bearing spirals and huge gyrations of the 
air, ascribe to the latter a cohesive action like that which we 
know to operate in the corresponding liquid forms? 
ile thus expressing my dissent from such an application of 
Plateau’s theory of liquid jets, and from any other view which 
would aseribe an effective cohesion to matterin the gaseous 
state, I gladly bear testimony to the clearness with which Prof. 
eConte has presented his suggestions in its favor, as well as to 
the interest of other points in his paper. 
Art. Il—Enquiries concerning Stellar Occultations by the Moon 
and the Planets,—experiments upon Light and Magnitude in re- 
lation to Vision; by Prof. A. C. Twinina. 
Ir, by the employment of any advanced means or modes of 
observation, or by any additional pains-taking, the occultations 
of fixed stars by the moon or the planets can be made more 
clearly and more frequently than at present a visibly determirt- 
ate phenomenon, an important acquisition will be gained to as- 
tronomy. The illuminated discs of these occulting bodies, hay- 
: ing an enormous area relatively to the minute stellar discs, over- 
F power the latter at and near the place of contact, notwithstanding 
| the difference of intensity in the two illuminations. Many or- 
ders of the telescopic stars are thereby excluded from this class 
: of observations. Stow far the means which it is my present pur- 
pose to propose can be made available has not yet been deter- 
mined instrumentally,—but they follow as a t inference 
from the relative law of light and vision experimentally devel- 
oped by myself, as will be shown before I have done. The 
means are so simple and obvious that, for years, and ever since 
they occurred to me, it has appea urprising that something 
of the kind had not been eiiplnyed-at once, as soon as the equa- 
torial movement came to be applied to telescopes. But the ob- 
ject of this paper includes, also, certain 6 Pao of the class 
of observations above mentioned, which do not appear hitherto 
to have been explicitly noticed. To these, in the outset, a brief 
attention will be given. i ae 
