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XXXII.— NOTES OIsT THE MICEOSCOPICAL CHAEACTEE OF 

 THE YOLCAlSriC ASH EEOM KEAKATOA. Br J. 

 JOLY, B, E., Assistant to the Professor of Engineering, 

 Trinity College, Dublin. Plates XII. and XIII. 



[Read, March 17, 1884.] 



On the 26th of August, 1883, the Norwegian barque Borjild 

 {Captain Amundsen), on her way from Cherribon to Anjers, cast 

 anchor off the east coast of the Great Kombuis Island, some 

 seventy-five miles to the north-east of Krakatoa. Here she re- 

 mained during the period of the eruption ; volcanic ash falling on 

 her decks from 6 a.m. to 6 p.m on the 27th. On that day, at 

 2 P.M., the darkness, due to absorption by the great layer of dust 

 above them, was described as being so intense that mutual recogni- 

 tion by vision was impossible. 



In the month of February, during the stay of the Borjild 

 at Dublin, a portion of this ash was, through the kindness of 

 Mr. Hogg, of Trinity College, obtained by the author. The 

 examination of this ash forms the subject of the following notes. 



Mere inspection with a lens shows the ash to consist principally 

 of vesicular fragments of pumice interspersed with vitreous and 

 crystalline particles. Before dealing with these it is interesting 

 to note the presence, as of accidental origin, of 



Sodium Chloride. — The presence of this substance may readily 

 be demonstrated by taste ; or by immersing in distilled water and 

 testing. Mr. Moss, who first called attention to it, estimated it to 

 be present to the extent of 0*8 per cent. 



Organic Marine Remains. — Those noticed were foraminifera, 

 of which some quite perfect shells were found, and also frag- 

 ments of starfish (identified by Professor SoUas) . Similar remains 

 were removed from the external cells of a specimen of the " floating 

 pumice," picked up by the Borjild in the Straits of Sunda. 



Perfect identity, mineralogically, seems to exist between this 

 floating pumice and the ash. Larger crystals may, however, be 

 obtained from the former than occurred in the latter. Feldspars 



2 D 2 



