236 A. E. Barlow — Relations of the 



Calculated for 



Found. CsHgClol 2 . 



Caesium.. 33-38 33-14 33-63 



Mercury 26*71 25-28 



Chlorine- S*87 9-01 S'98 



Iodine ,_ 30-85 30-17 32-11 



99-81 100-00 



When it was attempted to make a chloro-iodide containing 

 more mercuric iodide than this, a nearly pure double-iodide 

 was formed by exchange of halogens. 



Calculated for 

 Found. Cs 2 Hg 3 I 8 . 



Caesium 13-76 14-13 



Mercury 33*49 31*88 



Chlorine u*16 • 0*00 



Iodine 50*74 53*99 



98*15- 100-00 



The investigation of double-halides will be continued in this 

 laboratory, and it is hoped that a further study of the caesium 

 salts will lead to a better knowledge of this class of compounds 

 in general than we now possess. 



In conclusion, it gives me pleasure to express my gratitude 

 to my colleague, Professor Penfield, for his hearty cooperation 

 in undertaking the crystal lographic examination of the com- 

 pounds which have been described. His results have been 

 freely used in the foregoing descriptions, and they will be 

 given in detail in a future article. 



Sheffield Scientific School, New Haven, 

 Conn., May, 1S92. 



Art. XXX. — On the relations of the Laurentian and Huron- 

 ian on the North Side of Lake Huron • by Alfred E. 

 Barlow. 



[Published by permission of Dr. Selvvyn, Director, Geological Survey of Canada.] 



In this Journal for March, 1892, there appears an article on 

 " The Structural Relations of the Huronian and Basement 

 Complex on the North side of Lake Huron " by Messrs. Pum- 

 pelly and Tan Hise. On page 228 they refer to an article by 

 me " On the Contact between the Laurentian and Huronian 

 north of Lake Huron'' which was published in the American 

 Geologist (vol. vi, 1890, pp. 19-32). The region to which 

 my paper referred might better have been defined as north-east 

 rather than north, as the descriptions related only to certain 



