Dr. H. Hiclis — Cambrian Rocks of N. America. 155 



the valley into two lakes. On the east of the Frederikshaab glacier 

 is the lake Tasersuak, bounded on the north by the " Nunatak " 

 Kangarsuk, and stopped at its lower end by the Frederikshaab 

 glacier, and having a tongue of the ice-sheet entering into it at the 

 upper end. 



The erosive power of an ice-sheet is well seen by a glance at the 

 observations made upon the rivers which flow into the fjords of 

 Nagsugtok and Isortok, and which have their origin at the ends of 

 the tongues of ice which occupy the valleys continuous with these 

 fjords.i rj^ij^Q j.j^gj. fj.Q,-^ ^j^g £j.g^ contained only 200—225 grammes 

 of mud per cubic metre of water in the month of July, whilst the 

 second in the month of June enclosed 9129 to 974.4 grammes. This 

 is compared with the amount carried by the Aar where it emerges 

 from the glacier ; it there contains only 142 grammes. The great 

 difference presented by the rivers which fall into the two fjords is 

 attributed to the fact that the ice moves with much greater speed 

 towards the fjord of Isortok than towards that of Nagsugtok, It is 

 calculated that the quantity of fine mud carried into the former of 

 these fjords amounts to 4062 million kilogrammes per day. This 

 mud is deposited in the interior of the fjord, which is filled up to 

 such an extent in its upper portion that even flat boats cannot pass 

 up it. What a powerful machine for the formation of the fine clay 

 of " till " is here ! 



At the time when the Pennine Chain was nearly buried by the 

 great ice-sheet from the west and north-west, the parts which stood 

 out above the ice may still have possessed a meagre flora, for plants 

 are found upon Jensen's Nunatakker which, as already stated, are 

 situated about forty English miles from the edge of the ice, and have 

 an elevation of over 5000 feet. Amongst these plants are Draba 

 alpina and Potentiila nivea. Herr Kornerup has collected altogether 

 64 species of plants from various "Nunatakker." 



Oljservations have been taken by members of the various expedi- 

 tions as to the former extension of the ice, with the result that it is 

 found to have stretched much further seaward in the period of great 

 glaciation, but at the same time its height does not appear to have 

 risen very much above the present level, for the summits of many 

 mountains along the littoral show no traces of former glaciation. 

 This seems to indicate that the thickness of the ice depends rather 

 on the elevation of the country than on the intensity of the cold. 



I have written the above slight sketch in hopes of calling attention 

 to the importance of the results obtained by the Danish explorers in 

 Greenland, to those who wish to elucidate fully the history of the 

 ice-sheets of our own country. 



IV. — The Cambrian Eooks of North America. 

 By Henky Hicks, M.D., F.R.S., F.G.S., etc. 



CONSIDERABLE attention has been given of late years to the 

 faunas of the rocks in North America considered to be the 

 equivalents of the rocks usually classed as Cambrian in this country, 

 1 Meddelelser, part ii. 



