520 Chronicles of Science. [Oct., 



The deduced longitude of Eiviere du Loup is 4 h. 38 m. 10*295 s. 



An account of the recent transit of Mercury, as seen at Vizaga- 

 patam by Mr. A. V. Nursing Kow (a Hindoo astronomer), contains 

 some points of interest. Mr. Eow and some of his friends noticed 

 that near the middle of the transit a " wavy tint of light " darted 

 from the upper edge of the planet. The light was occasionally 

 disturbed, but continued visible for some time. No change of focal 

 length or of the eye-piece employed had any effect on the phenomenon. 

 We do not remember any instance of a phenomenon of this sort 

 having been noticed before during a transit of Mercury. As the 

 Astronomer Koyal for Scotland remarks, it is not easy to explain 

 the significance of so peculiar a featm-e. 



Major Tennant supphes an interesting note on the preparations 

 desirable for photographic observations of such phenomena as 

 transits of Venus. He believes that this method of utilizmg a 

 transit is a very valuable one, though he considers that it should be 

 subjected to trial before being unreservedly trusted. He remarks 

 that a reflecting telescope with unsilvered glass mirrors would give 

 comparatively little light ; and still less if the image were optically 

 enlarged. This point is of importance in connection with the ques- 

 tion of instrumental distortion. In a Newtonian telescope, a convex 

 or concave lens achromatized for the actinic rays might be used ; 

 or the telescope might be a Cassegrainian, an arrangement which 

 would be more compact than the other. An " instantaneous shut- 

 ter " would allow a fairly large aperture to be used, and " this 

 having its centre-part removed would give good definition." He 

 suggests a new mode of releasing the shutter. At Kew it is held 

 against a spring by a thread which is cut with scissors. Major 

 Tennant proposes that it should be retained by an electro-magnet, 

 and that the current forming this should pass through a chrono- 

 graph. Thus if an observer at a separate telescope had a break- 

 circuit key, he could at any moment photographically record a 

 phenomenon he saw and the instant of its occurrence, 



Mr. De la line, remarking on Major Tennant's paper, expresses 

 his preference for a Newtonian reflector ; the heat emergmg from 

 the back of the principal mirror, wlien either the Cassegrainian or 

 Gregorian forms are used, would seriously interfere, he remarks, 

 with the success of photographic manipulations. 



Both papers show the importance of a complete investigation of 

 all the circumstances of the coming transits. 



Major Tennant suggests that preparations should be made for 

 observing the total eclipse of 1871 in the south of India. He does 

 not comment upon the nature of the echpse, which we should have 

 thought little suited for the sort of observations he suggests. In 

 South India the totality will last little over two minutes. 



Mr. Baxendell discusses the nature of the corona seen round 



