PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 7 
February 6, 1884. 
J. W. Horns, Esq., F.R.S., President, in the Chair. 
Edward John Dunn, Esq., Oaklands, Claremont, near Cape Town, 
was elected a Fellow, and Dr. Joseph Szabd, of Buda-Pest, a 
Foreign Member of the Society. 
The List of Donations to the Library was read. 
The following communications were read :— 
1. “ A Delta in Miniature.—Twenty-seven years’ work.” By T. 
Mellard Reade, Esq., F'.G.S. 
2. “On the Nature and Relations of the Jurassic Deposits which 
underlie London.” By Prof. John W. Judd, F.R.S., Sec.G.8. With 
an Introductory Note on a Deep Boring at Richmond, Surrey, by 
Collett Homersham, Hsq., Assoc. M. Inst. C.E., F.G.S. 
Prof. Bonnry called attention to a rock-specimen exhibited by 
Mr. R. N. Worth, F.G.8., and by him named Trowlesworthite. It 
consisted chiefly of reddish orthoclase, purple fluor, and black schorl, 
in intimate association with quartz, and was found by Mr. Worth 
as a loose block on Trowlesworthy Tor. The rock appeared to be 
the result of a peculiar alteration of the granite of the district, in 
which black mica had been altered into tourmaline, some of the 
felspar had been replaced by schorl and quartz, and the original 
quartz constituents by fluor spar. Professor Bonney, who had ex- 
amined the rock microscopically for Mr. Worth, stated the reasons 
which led him to believe that the last-named unusual change had 
taken place. : 
The following specimens were exhibited :— 
Specimens, exhibited by Prof. J. W. Judd, F.R.S., Sec.G.S., and 
C. Homersham, Esq., F.G.S., in illustration of their paper. 
A specimen of Trowlesworthite, exhibited by R. N. Worth, Esq., 
