33. 



ON THE METEORIC SHOWER OF NOVEMBER, 1866. 

 [From the Proceedings of the Cambridge Philosophical Society. Vol. n.] 



THE author described the instrument used in the observation of the 

 Meteors, and mentioned the various hypotheses which have been advanced 

 concerning the orbit of these bodies ; he explained the calculations which 

 he had made to determine this, and shewed that the attractions of the 

 Earth, Jupiter, Saturn and Uranus were nearly sufficient to account for a 

 hitherto unexplained change of about 29 minutes in the position of the 

 nodes of the orbit in each period of 33 years. He called attention to the 

 fact that the orbit calculated appeared to coincide very nearly with those 

 of certain comets ; and held that the latter were elongated ellipses with a 

 periodic time of 33 years. 



[The instrument consists of an axle which is mounted in all respects as the 

 axle of a theodolite. To one end of the axle is fixed a graduated circle, as in the 

 theodolite, which marks when the line of sight of the instrument is horizontal. 



To the other end of the axle and at right angles to it is a bar to which are 

 attached a V-shaped piece of metal, a, and an eyepiece. 



On the eyepiece, about 3 in. from the eye towards the V is a thin bar, b, with 

 a notch at its middle point, which can turn about the line in which the instrument 

 is pointing. 



Attached to the thin bar is a circle divided to degrees, which marks when 

 the bar is exactly parallel to the upper edge of the V with the notch downwards. 



The circle is provided with a vernier of 12 divisions, so that angles can be read 

 to 5'. The point of the V is on the axis or line of sight about which the thin 

 bar turns. 



The altitude and azimuth of any point in the line of sight can be read off on 

 the vertical and horizontal circles of the instrument. 



When the instrument is directed to a meteor, the thin bar can be readily turned 

 with its circle so as to coincide in direction with the apparent path of the meteor 

 across the field of view.] 



