1897.] NEW YORK ACADEMY OF SCIENCES. Ill 



a few inches or feet beneath the surface, covered with a vigorous 

 growth of millepores and corals. These are extensive in the la- 

 goon and Castle harbor, in all manj^ square miles. They are 

 less extensive in Harrington sound, where they are found mostl}'' 

 on the easterly shores, but, as will appear further on, their equiva- 

 lents are present in other parts of the sound. These " flats " 

 are often spoken of as coral reefs and somewhat similar though 

 smaller patches in the lagoon and off" the south shore are called 

 serpuline reefs. But even a casual examination suffices to show 

 that they are merely planed oft' hills or islands to which the 

 corals and other animals attached themselves. The process is 

 clear enough in all its stages from the beginnings of undercut- 

 ting to the final making of the plane, with the prompt occupa- 

 tion of every new surface b3' corals, sponges, raollusks and the 

 rest. Wherever they could be examined, these flats proved to 

 be merely sandstone or, in some cases, limestone planed off" and 

 covered by a thin growth of coral or millepore. Agassiz* saw 

 this distinctly and recognized successive planations by wave ac- 

 tion. In them and the basins surrounding them we read much 

 of the history of the Bermudas. 



In tracing out the character of the submerged surface within 

 the elliptical area of 220 square miles, one's main dependence 

 must be the Admiralty map, which has been republished by the 

 Ilydrographic Utlice of the United States Navy.-j- This map, 

 giving the soundings obtained in the several bodies of water, 

 shows that the sounds and harbors, as well as the lagoon, are 

 not simple basins, but in each case a congeries of basins, united 

 often by water so shoal as hardly to suffice for the smallest 

 boats. Let us look at the details. 



The Reef and the Lagoon. 



The great reef or ledge flats, extending from the southern 

 point of the islands round to the northeast corner and continuous 

 with the so-called bounding reef on the southeasterly side, varies 

 in the main portion from one mile to two miles and a-half in 

 width. It is covered, for the most part, b}' from three to twenty- 

 five feet of water, though in many portions the depth is less and 

 in others much greater. Its borders are indented by bays and 

 show submerged peninsulas and islands. Chains of submerged 

 islands, occasionally reaching to within a few inches of the sur- 

 face or even above it at low water, extend from the reef and are 



*Loc. cit., p. 257. 



t The map accompanying this paper is copied from that published in The Atlantic. 

 It fails to show many of the features emphasized in the succeeding pages, but it ex- 

 hibits the geographical relation of the localities and gives a good general conception 

 of the conditions in the submerged areas. 



