Henry Woodtvard — Address to the Geologists'' Associatio'n. 541 



an excellent illustration of what a period of less than a thousand 

 years can effect as regards climatal conditions by a very slight de- 

 flection in an oceanic current. 



In 983 some Norwegian adventurers from Iceland discovered the 

 continent of Greenland. They planted a colony on the eastern 

 coast, and the intercourse between this colony, Iceland, and Denmark, 

 was continued till the beginning of the fifteenth century. 



From this date, owing to an insetting of the Arctic current and a 

 consequent gradual increase of the Arctic ice upon the coast, the 

 colony became inaccessible, and the records of it disappear from 

 history. In 1579, 1588, 1605, 1607, 1652, 1670, 1671, 1751, and so 

 on, down to our own time, the intrepid Danes have striven to re- 

 open communication with their lost eastern colony, but all in vain, the 

 pitiless. "ice- pack" has shut in this emerald coast, whose valleys, well 

 stocked with reindeer and covered with soft verdure, first attracted 

 the desire of these hardy Norsemen to make it their home. It would 

 be interesting to ascertain whether the increasing cold has fostered 

 the growth of glaciers to such an extent as to fill the eastern valleys 

 down to the sea-margin, or whether the little Danish colony has held 

 its own, secluded from the outer world, and has maintained its 

 primitive existence in this ice-bound land, occupying, as the western 

 Greenlanders do, the sea-shore and the tract of low valleys border- 

 ing on the coast, which may have remained clear of ice, and which 

 yield in the short hot arctic summer a fair amount of vegetation. 



Turning our attention for a moment to the Eocky Mountains of 

 North America, it is of great interest to the geologist to learn that 

 evidences of the declining energies of two great forces — volcanic 

 and glacial action — have been met with in this range. 



The first is attested in the wonderful series of geysers, mud- 

 volcanos, and thermal springs discovered and described by Dr. F. V. 

 Hayden, U.S. Geologist, in Wyoming Territory;^ the second by the 

 discovery of still active glaciers in the Yosemite Valley and vicinity, 

 in California, described by Prof. J. Le Conte and Mr. John Muir.^ 



Did space permit, I would allude to the labours of the American 

 Geological Surveyors ; to those of the Geological Survey of India ; 

 of our home Survey ; and of that still more wonderful sub-marine 

 Survey, begun in H. M.S. -Ships "Porcupine" and "Lightning "during 

 1868, '69, '70 ; and now being systematically carried on by the 

 Admiralty in H. M. S.-S. "Challenger" by Prof. Wyville Thomson 

 and his staff. But I find my time, and I fear your patience, will 

 alike be exhausted ere I conclude. 



I would fain bear testimony to the valuable work which has been 

 carried on by members of this Association in the Menevian Eocks of 

 St. David's. This task, initiated by Mr. Henry Hicks, F.G.S.,=* and 



^ See Dana and Silliman's American Journal of Science, 1872, third series, vol. iii. 

 p. 161, and p. 295. 



* See Dana and Silliman's American Journal of Science, 1873, vol. v. p. 69, and 

 p. 325. 



3 Eesearches in the Lingula Flags of South "Wales (Joint Eeport to British Asso- 

 ciation, Birmingham, 1865), Geol. Mag. 1866, Vol. III. p. 27. On Lingulella 

 from the Lower Cambrian, Quart. Journ. Geol. Soc. 1867, vol. xxiii. p. 339. On 



