222 Transits of Jupiter's Satellites. 



up to that ring. The whole agreed more with Gr/s description 

 than B. and M/s figure, in the progressive shortening of the 

 oblique walls, towards the "N., so as to give fairly one-half of 

 the design of a tapering leaf. But my remark at the time was, 

 te the whole object looked coarse, and though curiously ar- 

 ranged, would never have given me the idea of an artificial 

 production." The following night I could still make it out as 

 a previously known figure, and could even count up four 

 valleys in feeble relief. The crater (a) appeared to contain 

 another interior ring, concurrent with the larger one on its E. 

 side. The terminator lay at this time a very little beyond the 

 E. end of Glavius (50), and wall of BulliaJdus (60), and its 

 own diameter beyond Copernicus (30). From this it appears 

 that it is by no means a difficult object, and may be made out 

 under much higher illumination than Gr. would have led us to 

 suppose : and it is worth looking for, not merely for its 

 curious parallelism, but still more as very suitable for studying 

 the question, which after all seems open to further enquiry, of 

 temporary atmospheric obscuration. It is situated in a region 

 where the effect of variations in perspective foreshortening 

 from libration may be neglected, and since none of the prin- 

 cipal lines run in the parallel of latitude, there is little reason 

 to anticipate illusion from the change of the direction of illumi- 

 nation due to the lunar seasons. Any permanent features 

 ought, therefore, to be always equally visible in corresponding 

 circumstances : the direct observations of the discoverer, and 

 the fruitless searches of L., and B. and M., who not only ex- 

 amined but drew the region in detail, would lead to a suspicion 

 that they are not so. Future study only can decide ; and if it 

 should be found that there are variations, not explicable by 

 changes in the angles of illumination and vision, we must look 

 further for the cause. The existence of a lunar atmosphere is 

 denied upon arguments of much cogency ; but the question 

 cannot be considered as finally at rest; and the region before us 

 may be found especially suited for its decision, since from its 

 low-lying, and at the same time irregular and complicated 

 character it may be supposed highly favourable for the exhibi- 

 tion of atmospheric influence. As such, its strict examination 

 is commended to those who love to trace the footsteps of the 

 Maker of all things in the manifold exercise of His creative 

 power. 



TRANSITS OF JUPITEE'S SATELLITES. 



Oct. 1st. II. egress, 7h. 2Gm., Ditto shadow, 9h. 8m. — 



h'd. III. egress, 7h. 51m. Ditto shadow ingress, 7h. 52m. 



Ditto ditto egress, llh. 2'.>m. — Gth. I. ingress, 9h. 25m. Ditto 



shadow, lOh. 22m. I. egress, llh. 41m. Ditto shadow, 12h. 





