740 



SCIENCE. 



[X. S. Vol. XXI. No. 541. 



contribution to our knowledge of the physical 

 and geological conditions of the same section 

 of the coast, as hitherto the only scientific 

 studies of the Brazilian coral reefs were those 

 of Hartt on the reefs near the Abrolhos and 

 of Eathbun on that of Itaparica in the bay of 

 Bahia. The coral reef-fringed section of the 

 Brazilian coast extends from near the equator 

 to 18° south latitude, but for nearly half of 

 this long line, from Rio Grande do Norte 

 northward, the various types of reef — sand- 

 stone, coral and underlying rock — can not at 

 present be discriminated. The coral reefs are 

 broken by many and large gaps, for some of 

 which no apparent reason can be given. With 

 the exception of the Kocas, which seems to be 

 a true atoll rising from deep water, all the 

 reefs are built up on the submerged conti- 

 nental shelf and are fringing and barrier reefs. 

 They are usually narrow, ten to fifty meters in 

 width, but in the case of the large barrier reefs 

 may attain a width of thirty kilometers. The 

 near-shore reefs are quite thin, probably not 

 exceeding a thickness of ten meters, and a 

 hundred meters is presumed to be the maxi- 

 mum thickness of the outlying barrier reefs. 



For the most part the reefs have reached 

 the upper limit of growth and are now dead 

 on top, though still growing laterally. None, 

 however, are known that have been elevated 

 above tide level. In age they are presumed 

 to date back to Tertiary times, since they rise 

 from a shelf due to a great depression pre- 

 sumed to be of early Pliocene date. Coral 

 rock has been observed both beneath and on 

 top of sandstone reef rock and possibly some 

 ■coral reefs rise from a base furnished by sub- 

 merged examples of sandstone reefs. The 

 coral polyp fauna found on the reefs contains 

 twenty-eight species and is more closely re- 

 lated to that of the West Indies than to any 

 other known coral fauna. 



One of the points of greatest geological in- 

 terest brought out by this study of the coral 

 reefs is that a process of dolomitization of the 

 reef rock is going on in the open sea, thus 

 rendering unnecessary the ' salt-pan ' hypoth- 

 esis that has been appealed to in the cases 

 hitherto noted of a higher proportion of mag- 



nesia in rocks of coral origin than in the 

 skeletons of the corals themselves. 



Dr. Branner states that the opportunity for 

 completing his reef studies, commenced many 

 years ago, was provided by Professor Alex- 

 ander Agassiz. Both these gentlemen are, 

 therefore, to be congratulated on the impor- 

 tance of the results achieved and presented in 

 this splendid memoir, and it is greatly to be 

 desired that these results will stimulate them 

 to promote a similar study of that biologic 

 and geologic terra incognita, the northern sec- 

 tion of the reef-bound Brazilian coast, which, 

 on account of the peculiar conditions of winds 

 and currents, can only be explored by the use 

 of steam vessels. Orville A. Derby. 



CoMMissAo Geographica e Geologica de 

 Sao Paulo, Brazil, 

 December 26, 1904. 



SCIENTIFIC JOURNALS AND ARTICLES. 

 The April number (volume 11, number 7) 

 of the Bulletin of the American Mathematical 

 Society contains the following articles : Eeport 

 of the February Meeting of the American 

 Mathematical Society, by F. N. Cole; Eeport 

 of the December Meeting of the Chicago Sec- 

 tion, by T. F. Holgate; 'Mathematics at the 

 St. Louis Congress, September 20, 22 and 24, 

 1904,' by H. S. White; 'The Use of Hyper- 

 complex Numbers in Certain Problems of the 

 Modular Group,' by J. W. Young ; ' Extension 

 of a Theorem due to Sylow,' by G. A. Miller ; 

 ' Note on Isothermal Curves and One-Para- 

 meter Groups of Conformal Transformations 

 in the Plane,' by C. L. Bouton; Eeview of 

 Arendt's Dirichlet's Definite Integrals, by 

 Virgil Snyder ; ' The Theta Functions ' (Ee- 

 view of Ej-azer's Thetafunktionen and Eost's 

 Eiemann'sche Thetafunktionen), by J. I. 

 Hutchinson; Eeview of Hilton's Mathematical 

 Crystallography, by E. P. Baker ; ' The Theory 

 of Electricity ' (Review of Abraham and Fop- 

 pie's Theorie der Elektricitat), by E. B. Wil- 

 son; Notes; New Publications. 



The April number (volume 6, number 2) 

 of the Transactions of the American Mathe- 

 matical Society contains the following papers: 



E. J. WiLCZYNSKi : ' General projective theory 

 of space curves.' 



