INTRODUCTION. 3 



The specimens obtained by the lead did not suffice to give a true 

 idea of the deep-sea fauna. The Foraminifera alone were numerous 

 enough to give an idea of their distribution, which is approximately 

 attempted by different signs and colors on subdivision B of the same 

 map. representing the approaches to New York. 



To extend our knowledge, therefore. Professor B. Peirce. when he 

 assumed the superintendence of the Coast Survey, after the death of 

 Professor Bache. ordered, at the instigation of Professor Agassiz, a 

 more thorough exploration by means of the dredge* A beginning 

 was made in 1867, and the work continued during part of the working 

 seasons of 1868 and 1869. 



The ground explored is the part of the course of the Gulf Stream 

 known as the Straits of Florida. (See map. Plate VIII.) Through 

 these the stream passes from the Gulf of Mexico into the Atlantic 

 Ocean. They run at first from west to east between the coast of 

 Cuba and the Florida Reef and Keys, then bend in a semicircular 

 sweep, to take afterwards a course nearly due north. On the outside 

 of the bend, the old Bahama Channel opens into the straits through 

 its two mouths, the St. Nicholas Channel and the Santaren Channel, 

 separated from each other by the Salt Key Bauk. In the part of the 

 channel running due north, it is bounded by the Bahama Banks on 

 the east and the Florida Reef on the west. 



In transverse sections of the channel the greatest depth is nearest 

 its southern or eastern shore, and in a longitudinal section the depth 

 diminishes in passing towards the north, finding its minimum in the 

 narrowest part between Cape Florida and the Bernini Islands, after 

 which it increases again. In a transverse section between Key West 

 and Havana, the greatest depth is 853 fathoms; between Sombrero 

 Light and Elbow or Double-Headed Shot Key, on the Salt Key Bank, 

 500 fathoms ; between Carysfort Reef and Orange Key, on the Great 

 Bahama Bank. 47-3 fathoms; and between Cape Florida and the Be- 

 rnini Islands, 370 fathoms. 



* I cannot resist the temptation to add a short historical note on that important instrument ot 

 the modern naturalist, — the dredge. The Museum of Comparative Zoology possesses in its library, 

 among the books formerly belonging to Professor de Koningk, the copy of O. F. Midler's Zoologia 

 Danica, used by Tilesius in the voyage of circumnavigation of Captain Krusenstern in the begin- 

 ning of this century. Tilesius, among many interesting remarks written on the fly-leaf, mentions 

 the dredge invented and used by Midler, and represented in the vignette of the title-page ; he 

 purchased it on his passage at Copenhagen, in 1803, from Vahl. Midler's collaborator, and used it 

 now and then during the voyage, though, as he admits, not often, as it took several sailors to handle 

 it, the rope alone weighing eighty pounds ! The expedition must have been decidedly short and 

 weak-handed. On their return the dredge was deposited in the collection of the Imperial Acad- 

 emy of Sciences of St. Petersburg. 



To O. F. Muller belongs the honor of having invented the dredge, very nearly in its more 

 modern form, and of having inaugurated its use by naturalists in a most successful manner. His 

 qnaint remarks on the hopes and disappointments of the dredger, in the Preface of the Zoologia 

 Danica, are worth reading. 



