296 Trof. Nordenskiold — Transport of Volcanic Bust. 



of the dust siliceous plates of diatoms, which, as Ehrenberg showed, 

 occur very frequently in the sand thrown out from volcanos, but are 

 completely absent in the matter now in question. 



Under the microscope the Haga dust has in many respects a 

 striking likeness to the finest dust from a so-called " Bologna drop"^ 

 that has sprung asunder, that is, a drop of glass which has been 

 cooled suddenly, and therefore, from the most inconsiderable cause, 

 for example, a scratch with a file on its surface, falls asunder to a fine 

 powder. Here we have possibly a hint as to the formation of this 

 dust. On the outbreak of the volcano, an immense quantity of 

 superheated steam and strongly compressed gases has violently 

 escaped out of the crater's lava-sea, and brought along with it masses 

 of its glowing contents more or less finely divided. Naturally the 

 particles of lava, which at first are in a molten state, not only solidify 

 suddenly, but are also cooled to a very low temperature in the upper 

 strata of the atmosphere, and thereby obtain the property of the 

 " Bologna drop," of springing asunder, with the least concussion or 

 shaking, to a fine dust. 



On the 30th March N.W. or W. winds prevailed in the regions 

 where the ashes fell, and it was soon supposed that the volcanic 

 outbreak which gave origin to the ash-rain took place on the 

 volcanic island lying to the westward in the Atlantic — Iceland. Here 

 the land itself appeared to wish to give a contribution to the cele- 

 bration of the people's thousand year fete by means of furious 

 salvos from a number of volcanos, partly new, partly old, for the 

 most part situated in desert and almost inaccessible regions in 

 the interior of the island. Our knowledge of these eruptions, 

 however, unfortunately is not as yet founded on any scientific 

 examination, and it is perhaps the less necessary to repeat here the 

 interesting accounts of those grand phenomena that have appeared 

 in the newspapers, as I expect to have an opportunity another year 

 of returning to the subject, since the region will probably be visited 

 next summer by a distinguished geologist, well acquainted with the 

 natural history of Iceland. I will only mention that the eruption 

 began in the month of December, 1874, and then continued with 

 shorter or longer intervals from numerous craters situated in the 

 interior of the country, partly on Dyngjufjall, partly in the northern 

 part of Yatnajokul, or in the region between these enormous glaciers 

 and the great snow-clad volcano Herdabreid. The most plentiful 

 ash -rain on Iceland itself took place in consequence of an eruption 

 which began at the place last mentioned on the 29th March, and the 

 ashes which fell in Scandinavia probably belong to the same point 

 of time, in which case less than twenty-four hours was required for 

 carrying the ashes from Iceland to Scandinavia, that is, for their 

 passing over a distance of 200 Swedish miles, or 2000 kilometres. 

 Geological science has recorded many accounts of the fall of volcanic 

 ashes, where the ashes have been carried by the wind to very 

 remote regions, among others that ashes had already been carried a 

 couple of centuries ago from Iceland to Bergen on the west coast of 

 ^ Known here as " Prince Rupert's Drops." 



