1868. | Astronomy. 561 
If Ptolemy had made all his observations in the manner suggested 
by Captain Drayson, an uniform error would have appeared in the 
resulting longitudes. But that method must be looked on as ex- 
ceptional, being (as Captain Drayson admits) “an extreme case, 
and one giving the greatest amount of error.” In ordinary cases 
oe would not produce nearly so large an error as 1° in lon- 
gitude. 
Mr. Cooke describes a new driving-clock for equatorials. In 
this arrangement the pendulum is a half-second’s one, with a heavy 
bob, adjusted by sliding the suspension through a fixed slit. The 
scape-wheel is a double one, each wheel having four teeth: the 
teeth of one wheel strike on one pallet, those of the other wheel 
on the other pallet. The wheels are arranged in the form of the 
letter U. At the end of one branch is the scape-wheel, at the end 
of the other is an air-fan. The large driving-wheel and barrel are 
situated at the bottom or bend of the U. The scape-wheel and the 
two next wheels have an intermittent motion; all the others have 
a continuous motion. We have not space to describe how the change 
from one motion to the other is effected. It appears, however, that 
the arrangement is perfectly satisfactory. Mr. Cooke considers 
that a clock constructed on the same principle, connected with and 
giving motion to a cylinder, would make an excellent chronograph. 
Mr. Browning describes two drawings of Jupiter, one made on 
September 12, 1867, with a 104-inch reflector, and the other on 
December 22, 1867, with his own 12}-inch reflector; in each case 
the power was 200. On both drawings a dark belt, to the north 
of the bright equatorial cloud-belt, is seen to have a rather uni- 
formly corrugated appearance on the lower or northern edge. As 
a similar marking appears in Mr. De la Rue’s well-known drawing 
of Jupiter, taken in October, 1856, Mr. Browning is inclined to 
think that the mark may possibly indicate the conformation of the 
actual surface of the planet, or at least some peculiar condition of 
the planet's atmosphere over a particular portion of Jupiter’s globe. 
Major Tennant supplies some interesting particulars respecting 
the Zodiacal Light as seen at Calcutta. He has always found the 
shape to be a portion of a long ellipse or parabola, ill-defined at 
the outlines, and fading away, with a marked condensation of light 
towards the axis and horizon. 
Linné still continues to attract the notice of observers. We 
have papers from Messrs. Webb, Prince, and Birt, on the appear- 
ance of this crater. The opinion seems to be gaining ground, 
however, that no change has really taken place on this part of the 
moon’s surface. 
Mr. Stone supplies an important paper “ Ona Determination of 
the Constant of Nutation from the Observations in North Polar Dis- 
tance of Polaris, Cephei 51, and 6 Urse Minoris So Me the 
Q 
