ADDENDA. 355 



sudden, what should I run foul of but Mount Ilecla ! The spec- 

 imens Nos. 15 and 16, like most of those which immediately pre- 

 cede, contain much calcareous mud and many calcareous Poly- 

 thalamia, from whose decay the mud was derived. By dissolving 

 out this mud by chlorohydric acid and examining the residue, the 

 specimens all left some fine sand, generally quartzose, and with 

 sharp angles ; but No. 15 and No. 16 gave a considerable portion 

 of well-characterized volcanic ashes, composed of glassy obsidian 

 and minute fragments of pumice. There can be no mistake about 

 it : the glassy matter ]ias the conchoidal fracture, the sharp edges, 

 and dark color of volcanic glass, while the grains of pumice, al- 

 though of microscopic size, show the contorted vesicles in which 

 was confined the gas which distended the mass. I find no evi- 

 dence of any violent abrasion in any of the specimens ; even in the 

 coarse ones from near tlie Banks, the matter has usually sharp 

 angles, and is such as might be dropped from icebergs as they 

 melt, without undergoing any subsequent abrasion or transporta- 

 tion." 



I could not perceive how these cinders could have got there 

 from Hecla or any of the extinct volcanoes of Iceland ; nor could 

 I perceive how, if they came from the volcanoes of intertropical 

 America, they should be found only in the narrow space between 

 the meridians of 25° and 26° 30^ W., along the parallel of 52°. I 

 asked the professor to "try back," and expressed the opinion, if 

 they came from the south, that they would, as far north as that 

 parallel, be found all the way across the eastern half of the At- 

 lantic, and as far toward the Irish coast as the deep water goes. 

 He did so, and immediately reported the presence of cinders in ev- 

 ery specimen along a line more than 1000 miles in length. 



"From No. 11 up to No. 20, inchisive of both,'" says he, "the 

 microscopic bits of pumice and obsidian (or smoky volcanic glass) 

 are unmistakably present. No. 10 I must look at again. I think 

 that it also has volcanic matter in it, but I must make another 

 special search for it before I pronounce positively. 



"The evidence of want of abrasion of the mineral matter, and 

 the presence of a large proportion of fine calcareous mud with 

 Gulf Stream forms, continues in all the specimens yet examined." 



Z 



