Pi'oceedings of Learned Societies. 299 



We shall postpone to another opportunity our remarks upon 

 other expedients of still greater practical value. 



TKANSITS OF JTJPITEE'S SATELLITES. 

 As the opposition of Jupiter takes place on the 12th, the 

 shadows of the satellites will be seen during the month in close 

 proximity to the bodies which cast them, varying, however, of 

 course, in this respect, from perspective, in proportion to the 

 distance of the satellite from its primary, and changing sides at 

 the time of opposition. The transits at convenient hours will 

 be the following : — May 1st. Shadow of I. passes off the disc at 

 llh. 8m., followed by the satellite at llh. 24m. 4th. Shadow 

 of III. enters at 9h. 31m., III. itself at lOh. 32m. ; their depar- 

 tures being at llh. 40m. and 12h. 15m. respectively. 5th. 

 Shadow of II. goes off at lOh. 35m. ; the satellite at lOh. 54m. 

 8th. Shadow of I. enters at lOh. 50m. ; I. at lOh. 57m. ; the 

 departures being at 13h. 2m. and 13h. 7m. 12th. II. enters at 

 lOh. 53m., 3s. after its shadow, and leaves at loh. 9m., 2s. 

 before it. If the planet were precisely in opposition, and also 

 in its node (or passage across the ecliptic), at the time of a 

 transit, the shadow would of course be invisible, being concealed 

 by the body of the satellite. This curious coincidence can but 

 seldom occur, but there will be an approximation to it on the 

 present occasion, as the planet will be in opposition with less 

 than 57' of N. latitude. 



PROCEEDINGS OF LEARNED SOCIETIES. 



BY W. B. TBGETMEIER. 



GEOLOGICAL SOCIETY.— March 23. 



New Fossils from the Lingula Flags. — Mr. J. W. Salter described 

 two new genera of Trilobites, and a new genus of sponge recently 

 discovered by Mr. Hicks in the hitherto scanty fauna of the Primor- 

 dial zone. He also remarked that the fauna of the Lingula flags 

 shows an approximation, in some of its genera, to Lower Silurian 

 forms, and some — the Shells and a Cystidean — are of genera com- 

 mon to both formations ; but the Crustacea, which are the surest 

 indices of the age of Palaeozoic rocks, are entirely of distinct genera ; 

 and their evidence quite outweighs that of the other fossils. The 

 Primordial zone is, moreover, in Britain separated from the Caradoc 

 and Llandeilo beds by the whole of the Tremadoc group, which are, 

 at least, 2000 feet thick. 



April 13. 



The Siliceous Springs in the Nevada Territory. — Mr. "W. P. 

 Blake communicated a description of the physical features of this 



