892 Scientific Intelligence * 
The mirror is made to pass across the convex leaden tool, by 
a rectilineal motion, while the mirror and the tool revolve, very 
slowly, with any required velocity, about their common axis, in 
opposite directions. The angular velocity of the mirror is for 
certain reasons twice the angular velocity of the leaden tool. 
Towards the end of the process an approximation may be made 
to a paraboloid, or to any conic section, by making the rotatory 
motion rapid, and the rectilineal motion short and slow, over a 
convex spherical surface, deficient by sectors, varying according 
to a certain law. 
Art. XXII.— SCIENTIFIC INTELLIGENCE, 
I. NATURAL PHILOSOPHY. 
ASTRONOMY. 
1. New Elements of the second Comet of 1822. — This comet, 
whose elliptical and parabolic elements we gave in our last Num- 
ber, was seen in October, and observed by Professor Shumacher 
and Dr Olbers. The following elements, calculated by Mr Ham 
sen, represent the observation of these astronomers : 
Time of Perihelion, 1822, Oct. 23. 5^725, at Altona *, near Hamburgh. 
Long, of Perihelion, .... 271° 53' 32" .4 
Long. Of Asc, Node, from the Mean Equinox of 1st September, 92 38 17 .9 
Inclination of Orbit, - - - - 52 36 51 .7 
Log. of shortest distance, ... - 0.0597898 
Motion, - - Retrograde. 
These elements, compared with the observations of Professor 
Schumacher and Dr Olbers, do not indicate an elliptical orbit. 
% BesseVs Survey of the Heavens.— That excellent and as- 
siduous astronomer, M. Bessel of Konigsberg, is engaged in an 
important work, containing a Survey of the Heavens in zones. 
The first part of the work will speedily appear. 
orTics. 
3. On the Double R fraction of Compressed Glass , and f 
Glass that is rapidly cooled.— Dr Brewster had long ago con- 
cluded, (to Philosophical Transactions 1816, p. 46, and Id. 156, 
This place is 30 m 30 s East of Paris. 
