522 Chronicles of Science. [Oct., 



should be large, tliat its density relatively to tliat of the fluid should 

 be small, and that the surface common to the fluid and the bubble 

 should have as large an area as possible. To gain these points, and 

 to cause the temperature to have as small an efiect as possible upon 

 the length of the bubble, he proposes that the cylindrical form of 

 level should be abandoned, and the necessary cavity be cut out of a 

 rectangular prism of glass. He suggests mercury for the fluid and 

 hydrogen for the bubble. 



Mr. Hind supphes an important note respecting the transit of 

 Venus in 1874. M. Puiseux, who had independently calculated the 

 circumstances of the transit, had arrived at results somewhat dif- 

 ferent from those pubhshed by Mr. Hind in 1861. Mr. Hind has 

 placed the re-calculation of the elements in the hands of Mr. W. 

 Plummer, his assistant at Mr. Bishop's observatory, Twickenham, 

 and the result is that Mr. Hind's estimates are confirmed in a most 

 satisfactory manner. 



The June number of the Monthly Notices was not pubhshed by 

 the Society's printers until the middle of August, nearly six weeks 

 after the proper time. It contains six large maps by Mr. Proctor, 

 illustrating a paper on the transit of Venus. Of these, four repre- 

 sent the same features which had been exhibited in the Astronomer 

 Koyal's maps accompanying the December number of the Notices, 

 and show the efiects of changing the phase from the passage of 

 Venus's centre to the planet's internal contacts. The other two are 

 enlarged drawings of the features exhibited in our last number. 

 The corrections resulting from the former set are new, and some of 

 them, if established, would seem to be important. Thus Crozet 

 Island, which had been rejected on account of the low elevation of 

 the sun there at ingress, is shown to have the sun 5^ degrees higher 

 than had been supposed. The calculated solar elevation of 4^ 

 degrees at Bourbon Island is altered to 12^ degrees ; degrees at 

 Mauritius to 14 degrees; and IH degrees at Kodriguez to 19 

 degrees. These numbers all refer to ingress. As respects egress, 

 the most important change is from a calculated solar elevation of 

 11^ degrees at Chatham Island to one of 16 degrees. A number 

 of Indian stations before unnoticed are shoT\Ti to be among the best 

 available places for observing the retarded egress. 



Professor Brayley supplies an interesting paper on the nature 

 of the bridges of light seen across solar spots. He looks upon these 

 as the upper termination of vorticose flames. 



Mr. Stone gives a table of the probable errors of Greenwich 

 observations in zenith distance, estimated merely by their dis- 

 cordances from the separate means. More than 2000 observations 

 were employed in obtaining the errors. The probable error ranges 

 from 0" • 47 at the zenith to 0" ■ 60 half-way between the zenith and 

 the horizon ; thence to 0" • 70 at an elevation of 35° above the 



