262 THE PHYSICAL GEOGRAPHY OF THE SEA. 



bad in quality, yielding representatives of most of the great 

 groups of microscopic organisms usually found in marine sedi- 

 ments. 



" The predominant forms are silicious spicules of sponges. Va- 

 rious forms of these occur ; some long and spindle-shaped or acic- 

 ular, others pin-headed, some three-spined, etc., etc. 



" The Diatoms (silicious infusoria of Ehrenberg) are very few 

 in number, and mostly fragmentary. I found, however, some per- 

 fect valves of a Coscinodiscus. 



" The Foraminifera (Polythalamia of Ehrenburg) are very rare, 

 only one perfect shell being seen, with a few fragments of others. 



" The Polycistinise are present, and some species of Haliomma 

 were quite perfect. Fragments of other forms of this group indi- 

 cate that various interesting species might be obtained if we had 

 more of the material. 



754. "You see by the above that this deep-sounding differs 

 considerably from those obtained in the Atlantic. The Atlantic 

 soundings were almost wholly composed of calcareous shells of 

 the Foraminifera ; these, on the contrary, contain very few Fora- 

 minifera, and are of a silicious rather than of a calcareous nature. 

 This only makes the condition of things in the northern Atlantic 

 the more interesting, because," says this philosopher, " they prove 

 that deep water is not necessarily underlaid by foraminiferous de- 

 posits, and that some peculiar local conditions of temperature, cur- 

 rents, or geological substratum, have made the North Atlantic a 

 perfect vivarium for the calcareous forms. 



755. "The chart (Plate IX.) you send is very interesting, and 

 combines a wonderful amount of interesting phenomena. I have 

 little doubt that the history of the bottom of the ocean, as record- 

 ed by the sediments, would show a close relation to the facts de- 

 termined for the surface, besides many unexpected relations. I 

 am very anxious to get some soundings from the great ocean cur- 

 rent that, as shown in your chart, sweeps in through the Carib- 

 bean Sea and along the coast of Mexico and Texas. 



756. " I observe on your chart something which looks like a 

 sargasso sea southeast of Madagascar. Is it so ? Get sound- 

 ings, if possible, in these sargasso seas. Get soundings any where 



