2 INrRODUCTION. 



Tlie general results arc exhibited on tiie map acfoni])aiiviii,u' the 

 papei- in the Gco(jrnj>hixchc 3/t///iet7iti>f/t')i. um] i-epresenting the liottoni oil" 

 om- coast, from Cape Cod to the island of Cuha. The bottom is repre- 

 seiitcil of (Hff'erent colors, according to its principal constituents, wiiicii 

 are chiefly of four different kinds, — silicious sand, claj^ (the "mud" 

 or "ooze" of the charts), Globigerina mud, and coral sand or mud. 

 The silicious sand and the Globigerina mud have the greatest extent. 



Silicious sand is, with few exceptions, the prevailing material 

 from the shore to the hundred-fathoms line. It extends thus, skirting 

 the shore in a Ijioad band narrowing down to a ])oint as far .south 

 as Cape Florida, where it ceases altogether, and is replaced by the 

 coral formation, but reajjpears again on the west coast of the peninsula 

 near Cape Salde. 



Clay or mud occurs to a considerable extent only to the southward 

 of the Vinej-ard I.slands and eastern part of Long Island, in a region 

 known to navigators as the Block Island Soundings, and also in a series 

 of depressions off' the entrance to New York, called the MikI-IIuIcs. This 

 mud, of a stiff consistency and dark gray color (called blue or green by 

 the .sailors), may be derived froui the tertiary formations of -which 

 the bluffs oft' Gay Ili'ad, on the island of Martha's Vineyard, are the 

 remainder. 



Outside of the hundred-liithoui line we iiud the (ilobigeriua mud 

 forming the liottom of the Gulf Stream, whose wi'stern edge coincides 

 nearly with tiiat line of depth, and of the greater ])art of the 

 ocean, of the (iulf of ^Mexico, and of the deej) channels separating 

 the Uahama Banks from each other and i'rom the neigh))()ring lands. 

 The discovery of this important formation is generally attributed to 

 the expedition sent out under the connuand of liieutenant Berrynuui, 

 U. S. N., to sound out the path of the Atlantic Telegraph Cable in 

 IS");). Ill reality, however, the discovery was two years earlier. Lieu- 

 tenants Craven and Mailit, U. S. N., having severally, whilst engaged in 

 Gulf Stream explorations, in the service of the Coast Survey, ol)tained 

 spe(Mmens of this formation. (See Proceed. Aineric. Assoc, for Advanc. 

 of Science, Cleveland meeting. I800. ) 



An interesting di.scoveiN was made by Professor Bailey in examin- 

 ing these specimens, — the transformation of Foraminifera into green- 

 sand. The origin of the green-.sand grains in geological ibrmatious had 

 ])reviously been recognized by Ehrenberg; but here we have evidently 

 the process going on at the present day. particularly along a tract 

 at the meeting of the silicious and Globigerina bottoms off" the coast 

 of (leorgia and South Carolina, and also to a less extent in other places. 

 (The localities are indicated by black dotting on the map quoted; 

 near the mouth of New York Bay the .same sign indicates tertiary 

 green-.sand, the continuation of the New Jersev beds.) 



