42 Ohituary— Robert Etheridge, F.R.S. L. 8^ E., F.G.S. 



(100), (101) =40° r, (010), (111) =55° 26': it has a perfect 

 cleavage (100), and like Liveingite exhibits no oblique striations on 

 the planes in the zone [100, 001]. The other mineral is also 

 oblique with /3 = 89° 40', (100), (101) = 46° 18', and (010), 

 (111) =59° 56': it has a perfect cleavage (100), and like Rathite 

 exhibits numerous oblique striations on the planes in the zone 

 [100, 001]. On fine brilliant crystals of Sartorite recently obtained 

 by the author he has been able to confirm the oblique symmetry 

 which he had previously announced and to determine accurately the 

 elements^ = 88° 31', (100), (101) = 54° 45', (010), (111) = 69°52|'. 

 Amongst other specimens from the dolomite of the Lengenbach in 

 the Binnenthal, the author exhibited and described peculiar rounded 

 crystals of Galena resembling Seligmannite, Hyalophane crystals- 

 twinned according to the Carlsbad law and showing three new 

 forms, a green mica which was determined to be anorthic, Albit© 

 and Biotite, minerals which have not been hitherto recorded from 

 the locality, and Barytes in green crystals. Of specimens from the 

 Ofeiihorn, the author exhibited some remarkably fine crystals of 

 Anatase, and crystals of Laumontite, a mineral new to the locality. — 

 Mr. L. J. Spencer described crystals of Adamite from Chili, which 

 were remarkable for their strong pleochroism. — Mr. G. F. Herbert 

 Smith discussed the prismatic method of determining indices of 

 refraction. From observations of the angles of incidence and 

 deviation the refractive index and direction of the wave-front in the 

 crystalline medium could be found. By using pairs of faces in th& 

 same zone and different angles of incidence a series of refractive 

 indices is obtained, which, when plotted with the direction angle as 

 ordinate, gives in general a double curve. Three of the critical 

 values are the principal indices, the fourth corresponding to the 

 direction parallel to the zone-axis. The angles of polarisation with 

 respect to the zone-axis provide a means of discriminating between 

 the doubtful values. A description was given of an inverted 

 goniometer whereby observations could be made in media other 

 than air. 



c>:bxttj Jt^iRizr . 



ROBERT ETHERIDGE, F.R.S. L. & E,, F.G,S, 

 BoRX Decemiiek 3, 1819. Died Decewisek IS, 1903. 



In the closing days of the old year another veteran geologist has- 

 laid aside his hammer and gone to his rest, working up to the very 

 last of his long and active life at his favourite science. 



Tlie name of Robert Etheridge is well known to all the older 

 geologists, and, nntil liis retirement from the public service on the 

 31st December, 1891, he had been a familiar figure for 34 years in 

 the London geological world, 24 of which he was one of the 

 Palaeontologists to the Geological Survey and Museum in Jermyn 

 Street, while for ten years he was attached to the British Museum 



