CONTENTS. iii 



PAGE 



XIII. Account of an Extensive Mud-Slide in the Island of 



Malta. By A. Milward, Esq. (With a Plate.) 

 Communicated by the Author, . . .128 



XIV. An Attempt to illustrate the Origin of " Dirt-bands" 



in Glaciers. By A. Milward, Esq. Commu- 

 nicated by the Author, . . . . 134 



XV. Fifteenth Letter on Glaciers; containing Observa- 

 tions on the Analogies derived from Mud- Slides 

 on a large Scale, and from some processes in the 

 Arts, in favour of the Viscous Theory of Glaciers. 

 Addressed to the Rev. Dr Whewell, by Professor 

 Forbes. (With a Plate.) Communicated by the 

 Author, 139 



XVI. Geological Notes on the Valleys of the Rhine and 

 Rhone. By Robert Chambers, Esq., F.R.S.E., 

 &c. Communicated by the Author: — 



Alluvial Terraces and Deltas, . . . 149 



Ancient Lake-Beds, . . . . . 157 



Rock Smoothings and Erratic Blocks, . . 159 



XVII. On the Smoothed Rock Surfaces of the Porphyritic 

 Hills of Hohburg, near Wurzen. By Professor 

 Naumann, ...... 161 



XVIII. On Extracting Pure Gold from Alloys; and on the 

 Discovery of Tellurium in Virginia. By C. T. 

 Jackson, U. S., G. S. : — 



1. A new method of extracting Pure Gold from Alloys 



and from Ores ; by C. T. Jackson, U. S., G. S. 164 



2. Discovery of Tellurium in Virginia; by C. T. Jack- 

 son, U. S., G. S., 165 



