

THE DEPOSITvS OF THE SEA-BOTTOM. „ 



geriua clay is found farther from the land, the farther we proceed into the arctic regions, whether the 

 cause is that the Foraminifera have not so good conditions of life in the colder seas, and consequently 

 fall to the bottom in smaller quantity, or that the deposition of terrigenous ingredients is larger here 

 on account of the icebergs that are able, to a far higher degree than anything else, to carry clay, 

 sand, and stones far out on the sea, and deposit these ingredients there. 



The Globigerina clay is rather different, now very finely and purely clayey, now more sandy 

 to the touch, sometimes also rather coarsely sandy; this fact is exclusively due to the size of the 

 Globigerinse, as mineral particles upon the whole play a very inconspicuous part, and the other For- 

 aminifera also generally are found in rather small numbers. In the specimens of Globigerina clay, 

 southeast of Iceland, that have been designated as coarsely sandy-clayey, a greater number of Globi- 

 gerinse has been found measuring more than 0-5 mm in diameter, while such otherwise are rather rare 

 in the specimens; the specimens having a sandy-clayey consistency, contain Globigerinse only a little 

 smaller than 0*5 min , while the Globigerinse of the finer specimens measure about o - i — o-t," 1 " 1 in diameter. 

 The colour of the Globigerina clay is almost always light brown, sometimes with a slight grayish tint, 

 in a few cases light gray; when dry it is very light, sometimes almost quite white with a brownish 

 tint, generally not so coherent as the Transition clay. As the light colour arises from the contents 

 of Globigerinse and ooze of lime, the colour of the residue is always much darker than that of the 

 specimen, being generally brown or dark brown. 



The amount of carbonate of lime in the Globigerina clay varies from 2971 per ct to 71-43 

 per ct. in the specimen no 18 southwest of Iceland; the carbonate of lime of the 25 specimens 

 averages 46-06 per ct. ; if we calculate the average amount of carbonate of lime with regard to the 

 different depths we get: 



13 specimens from 500 — 1000 faths with an average of 47-06 per ct. of CaC0 3 

 9 — - 1000 — 1500 — — 4777 — — 



3 — - 1500 — 2000 — — 36-81 — — 



and thus it would seem, as if the amount of carbonic acid decreased with greather depth, but the 

 cause is only that the specimens have their origin from very different places presenting highly different 

 conditions for the deposits; a large portion of the specimens taken on the smallest depths, is from the 

 before mentioned ridge southwest of Iceland where the circumstances are highly favourable for the form- 

 ation of deposits with great contents of lime, while the specimens from the very greatest depths are found 

 near the south point of Greenland, where the circumstances must produce the contrary effect; within 

 the same territory the amount of carbonic acid will almost always be seen to increase with the depth, 

 when this latter is not large; but if the question be of deeper water than has been sounded by this 

 expedition, the amount of carbonic acid will be seen to decrease again by increasing depth ; this fact may 

 be seen from the following table taken from the account of the Challenger expedition; here was found in 



3 specimens under 500 faths 87-07 per ct. CaC0 3 



2 — from 500 to 1000 — 68-47 — — 



13 — — 1000 - 1500 — 63-69 — — 



35 — 1500 - 2000 — 72-66 — — 



49 — — 2000 - 2500 — 61-74 — — 



16 — over 2500 — 49'58 — — 



