1869.] Astronomy. 521 



the sun in total eclipses. He considers that the view taken by 

 M. Faye and the Astronomer Eoyal (who look upon the corona as 

 an atmospheric phenomenon) is wholly inadmissible. When " the 

 corona is seen to the greatest advantage, no part of the earth's 

 atmosphere within a considerable angular distance of the sun and 

 moon receives any direct sunlight, and therefore none can be 

 reflected from it." He considers that not merely the optical phe- 

 nomena of the corona, but " an immense number of magnetical and 

 temperatiire observations made in different parts of the world " can 

 be best explained by assuming the existence of an irregular nebulous 

 ring circulating about the sun nearly in the plane of the echptic, 

 and at a mean distance of • 169. 



Mr. Joynson has presented another series of drawings of Mars 

 to the Society. They are selected from ninety made at various 

 times during the recent opposition of the planet. The planet has 

 been so carefully scanned by the late Mr. Dawes, with his fine 

 8-inch refractor and his unsurpassed powers of vision, that one can 

 hardly imagine what useful object an observer can propose to him- 

 self in laboriously depicting the planet as it appears imder far 

 inferior powers. Nothing but a very powerful telescope can now 

 teach us anything new about the lands and seas of Mars. 



Professor Loomis shows that Mr. Tebbutt's observations of the 

 variation of the mysterious star 77 Argus may be explained by 

 assigning to the star a period of variation of sixty-seven years, 

 instead of the period of forty-six years obtained by Professor Wolf. 

 According to this view, the star has now reached its true minimum 

 of splendour, and we may probably soon expect to see it steadily 

 increasing. According to the best observations during the past 

 century, the star has no less than three distinct maxima of splendour 

 — two nearly equal and corresponding to a brightness exceeding 

 that of aU stars but Canopus and Sirius, the other corresponding to 

 the least brilliancy of a first-magnitude star. The variable has but 

 one minimum, corresponding to a brightness somewhat less than 

 that of a sixth-magnitude star. 



Mr. Browning describes a large sun-spot which was visible on 

 March 14th, 1869. From north to south the spot measured 

 14,400 miles; from west to east 19,600 miles. The umbra con- 

 tained three nuclei of very unequal dimensions, arranged nearly in 

 the form of an equilateral triangle. Two bridges crossed the spot 

 at an angle of about 40". These bridges presented the appearance 

 of broken twigs, lying mostly in the direction of the bridges' 

 length. 



On May 13th, Mr. Bidder saw a spot having a bridge of an 

 unusually attenuated shape, and spirally formed. 



Major Tennant suggests certain modifications in the construc- 

 tion of spirit-levels. He considers that the volume of the bubble 



