•£23 



1653] 



ANNUAL REPORT OF THE SUPERINTENDENT OF THE U. S. COAST SURVEY, 1851. 



81 



TORONTO, NOVEMBER, 1853. 



The Annual Report of the Superintendent of the Coast Sur- 

 vey, [U.S.] Showing the Progress cf that work during the 

 year 1851, pp. 558, accompanied by a Quarto Volume, 

 Map and Chart. 



This Report with its voluminous appendices, contains a variety 

 of official documents relating to the Coast Survey of the dated 

 States, many of which have no interest for the general reader, 

 while others will attract universal attention. The extracts from 

 the report of Professor Agassiz, to the Superintendent of the 

 Coast Survey, on the examination of the Florida reefs, keys and 

 coast, contain most interesting information respecting the forma- 

 tion, progress and decline of the coral reefs. A portion of these 

 we subjoin. 



On page 227 of the 1st Volume of this Journal will be found 

 the elaborate report of George Mathiot, Electrotypist, on the 

 eleetrotyping operations of the United States Coast Survey, 

 which forms the concluding portions of this important and elabo- 

 rate work. 



MODE OF FORMATION OF THE CORAL REEF. 



The reefs of Florida as they have been described in the 

 foregoing sketch of the topography of that state, and, indeed, the 

 separate parts of each of these reefs, in their extensive range 

 from north-east to south-west, present such varieties as will afford, 

 when judiciously combined, a complete history of the whole 

 process of their formation. 



Here we have groups of living corals, beginning to expand at 

 considerable depth, and forming isolated, disconnected patches, 

 the first rudiments, as it were, of an extensive new reef. There 

 we have a continuous range of similar corals in unbroken con- 

 tinuity for miles, or even hundreds of miles, rising at unequal 

 heights nearly to the surface. 



Here and there a few heads or large patches, or even extensive 

 flats of corals, reach the level of low water mark, and may 

 occasionally be seen above the surface of the waters, when the 

 sea is more agitated than by the simple action of the tides. In 

 other places coral sands or loose fragments of corals, larger or 

 smaller boulders, detached from lower parts of the living reef, are 

 thrown upon its dying summits, and there form accumulations of 

 solid materia], rising permanently above low water mark ; col- 

 lected sometimes in such quantities and at such heights as to 

 remain dry, stretching their naked heads above high water. 



In other places these accumulations of loose, dead materials 

 have entirely covered the once living corals, as far as the eye can 

 reach into the depth of the ocean : no sign of life is left, except 

 perhaps here and there an isolated bunch of some of those 

 species of corals which naturally grow scattered, or of those other 

 organisms which congregate around or upon coral reefs ; but the 

 increase of the reef by the natural growth of the reef-building 

 corals is at an end. Again, in other places, by the further 

 accumulation of such loose materials, and the peculiar mode of 

 aggregation which results from the action of the sea upon them, 

 and which will be more fully explained hereafter, extensive 

 islands are formed, ranging in the direction of the mam land, 

 which support them. Elsewhere we may find the whole extent 

 Vol. 2, No. 4, November, 1853. 



of the reef thus covered, while, after a still more protracted accu- 

 mulation, perhaps becomes united with some continental shore. 



Now, it must be obvious, that from a comparison of so many 

 separate stages of the growth of a coral reef, a correct insight 

 may be obtained into the process of its formation ; and, indeed, 

 in thus alluding to the different localities which came under our 

 own observation, we have already given a general history of its 

 progress, which we now proceed to illustrate more in detail. 



We would, however, first remark, that the extraordinary varie- 

 ties which exist in the natural condition of different parts of the 

 same reef, or of different reefs, when compared with each other, 

 fully explain the discrepancies between the reports which have 

 been obtained, respecting the reefs of Florida, prior to our- 

 investigations. 



It had been stated that the reefs consisted solely of living 

 corals; and, indeed, this report is true of the outer reef, which is- 

 called by all the inhabitants of Florida " the reef," par excellence, 

 and is unfounded only with regard to those few islands which 

 rise above the surface of the sea at Sand Key and the Sambos.. 

 Others, who had noticed only the larger accumulations of coral 

 fragments which occur on the shores of some islands forming 

 part of the Florida- reef, had reported the islands to be formed of 

 coral rocks ; while some who had, perhaps, observed the extensive 

 excavations made around Key West, have told us only of the 

 existence of oolitic and compact rocks, almost destitute of corals 

 or other remains of animal life ; and from still other localities 

 comes the opinion, that the rocks consist of nothing but more or 

 less disintegrated shells, cemented together. 



ON ANIMAL LIFE. 

 % ********* 



The fullness and variety of animal life is particularly obvious 

 within the boundaries of coral fields, the natural limits assigned 

 to the growth of these animals being those in which animals of 

 other classes range in greater profusion, and the coral reefs 

 themselves also affording very favourable circumstances for the 

 display of numerous living forms. Hence the extraordinary as- 

 semblage of all classes of animals upon the reef, where, beside? 

 those particular kinds of corals which contribute largely to its- 

 formation, we find upon it, or on the foundation from which it 

 rises, a great variety of other corals, which, though too insignifi- 

 cant in size to take a conspicuous part in building up these ex- 

 tensive accumlations of organic lime- work, add none the less their 

 small share in the work, contributing especially to fill up the 

 vacant spaces left by the more rapid and durable growth of the 

 larger kinds. They are to the giants of the reef what the more 

 slender parts are to the lords of the forest, adding the elegance 

 and delicacy of slighter forms to the strength, power, ani dura- 

 bility of their loftier companions. 



But besides the stony corals, we find in the reef a great variety 

 of soft polyps, either attached to the surface of dead corals, dead- 

 shells, or of the naked rocks, or boring into the coral sand and 

 mud. 



Such are different species of area, the date-fish among the- 

 mollusca, and many worms, especially serpula among articulates,, 

 the agency of which in the formation of the keys will be described 

 hereafter. All these animals and plants contribute, more or less,, 

 to augment the mass of solid materials which is accumulating 

 upon the reef, and increase its size. Not only are the hard parts 

 of shells, echinoderms, worms, or their broken fragments, heaped 

 among the detritus of the corals, but occasionally even'the bones 

 of fishes and turtles, which are very numerous along the reef r 

 may be found in. the coral formations. 



