PROCEEDINGS OE 



THE EOYAL SOCIETY. 



^ 1 ~ " :;r«ifi, r *v- 



vol. xxvi. / ^ No. 183. 



CONTENTS. S « v u '# j 



June 21, 1877 (continued). 



PAGE 



IX. On some hitherto Undescribed Optical Properties of Doubly Refracting 

 Crystals. — Preliminary Notice. By H. C. Sobby, F.R.S., President of 

 the Eoyal Microscopical and of the Mineralogical Societies 384 



X. On the Foci of Lines seen through a Crystalline Plate. By Gr. Gr. Stokes, 



M.A.. Sec. R.S 386 



XI. Notes on Physical Geology. — No. III. On the probable Age of the Conti- 

 nent of Asia and Europe ; and on the Absolute Measure of Geological 

 Time. By Rev. S. Hattghton, M.D., D.C.L., F.R.S., Professor of Greology 

 in the University of Dublin 401 



On the Increase in Resistance to the Passage of an Electric Current produced on 

 certain Wires by Stretching. By Hebbebt Xomlinson, B.A., Demonstrator 

 of Natural Philosophy, King's College, London 401 



ERRATA (No. 182). 



Page 357, line 4, delete the hyphen in material-like. 

 „ „ footnote, line 5 from bottom, for Helvingrove read Kelvingrove. 



Price One Shilling, 



