PROJECTED EXPLORATION OF ICELAND. 



227 



But the observation of modern glacial conditions in Iceland is not 

 the only way in which existing phenomena can be nsed with advan- 

 tage in the interpretation of by-gone history. The formation of the 

 gypseous and saliferous marls of the Triassic series is very imper- 

 fectly understood, and nowhere so well as in Iceland can be seen the 

 operations of mud- springs charged with muriates and sulphates, such 

 as form the well-marked features of the "red marl" deposits of 

 England, and which may have resulted from some such operations of 

 subterranean heat. 



The war between Huttonians and Wernerians is not quite so fierce 

 now as when Sir George Mackenzie, himself a stout supporter of the 

 great Scotchman, visited the volcanic tuffs and scoria? of Hecla ; but 

 many igneous minerals are yet unsolved, and very good help may be 

 given by a careful study of the " Pearlstones," silico-aluminous 

 deposits, and others so abundant in the volcanic regions of Iceland. 



Again, another field of observation was opened seventeen years 

 ago by Prof. Ehrenberg, and has not, to our knowledge, been entered 

 by any one since. Volcanic products erupted from the craters of 

 Iceland have been carried in the shape of " meteoric dust" to a dis- 

 tance of five hundred miles. A good example of this is the case of 

 the ship " Helena" of Copenhagen, covered with a layer of ashes and 

 dust when at a distance of five hundred and thirty- three English 

 miles south-east of Hecla. To this mountain, then in eruption, the 

 cloud of wind-blown volcanic matter was traced, and the result 

 showed that the same silicious- shelled infusoria contained in it were 

 also to be met with in the dust which had settled upon the flanks of 

 Hecla, and by colour, appearance, and contents, the transported dust 

 was identical with that which had settled upon near-lying places. 



In connection with this, Prof. Ehrenberg suggests that it would be 

 of the utmost value to secure samples of dry ashes of any kind that 

 have not been wetted since their eruption ; and that if any traveller 

 in the volcanic region was fortunate enough to be upon the mountain 

 while ash or dust of any kind was being emitted, it would be im- 

 portant to secure a specimen of such deposit before it had been sub- 

 jected to atmospheric or aqueous influences^ so that the important 

 question may be settled whether organic bodies do exist in matter 

 emitted from volcanic vents. 



