230 Scientific Intelligence. 



viable detail. After presenting the facts as to various reefs, 

 and the depths of the living corals, the limit of which he finds to 

 be beyond thirty fathoms, he presents his conclusion with 

 regard to the origin of the barrier reefs. He observes that, after 

 coral reefs have begun about an island, the detritus, made from 

 the corals, will collect in a band on the outer slope of the reef, at 

 depths near the limit usually attributed to growing coral, and 

 extend, as may be determined, by the presence, position and 

 slope of the declivities. In such a zone of detritus the corals do 

 not thrive. But below it the slopes may be gentle again, and 

 . there may be another zone of corals ; and when so, .the corals of 

 this outer zone may rise and make a surface reef, separate from 

 the first or fringing reef by a region of detritus; the outer reef so 

 made will be a barrier reef. An elevation in the region may 

 bring other parts of the sea-bottom about islands within coral 

 reef depths, and thus the process may be repeated and extended. 

 The objection to the theory that the depths inside of barrier reefs 

 are sometimes forty to sixty fathoms is met on the ground of the 

 possibility that the lower coral reef limit may be as great as this, 

 and on his own observation that "off the reef of Choiseul Bay I did 

 not seem to have reached the lower limit in soundings of forty 

 fathoms." Mr. Guppy states that his views are substantially the 

 same with those of Prof. Joseph Le Conte, as presented in his 

 paper on the Florida barrier reefs (this Journal, II, xxiii, 46). 

 Mr, Guppy gives other conclusion from his observations. 



What is needed to place the subject entirely above the level of 

 hypothesis is a series of generous borings in sevei'al atolls and 

 barrier reefs, as the writer has elsewhere suggested. It is not a 

 question, merely, as to how reefs have been made, but whether or 

 not great downward as well as upward change of level is possible 

 in Quaternary or recent times within the oceanic limits, and it 

 therefore calls for whatever expenditure may be necessary to 

 carry on such borings effectually. J. d. d. 



2. Fxjilorations in Florida; by Angelo Heilprin, 134 pp., 

 large Svo, with 20 plates. Philadelphia. Transactions of the 

 Wagner Free Institute of Science of Philadelphia. Published 

 under the direction of the Faculty, May, 1887. — The Wagner 

 Free Institute of Science in Philadelphia, was founded by the 

 late William Wagner, of that city, and sustained as an Insti- 

 tute of free lectures by his annual gifts for thirty years ; and at 

 his death, in January, 1885, all his property was bequeathed to 

 it. The faculty consists of four professors with Dr. Leidy as the 

 president. The trustees have appropriated part of the fund to aid 

 in original research, and the memoir of Mr. Heilprin is the first of 

 the reports thus obtained. 



The expedition to Florida was organized early in 1 886, with 

 the generous cooperation of the Academy of Natural Sciences and 

 Messrs. Joseph Willcox and C. H. Brock, who joined it, Mr. 

 Heilprin being put in scientific charge. The schooner Rambler 

 was chartered for the excursion. 



