514 



SCIENCE. 



[N. S. Vol. XV. No. 378. 



from solution, and there is nothing to indicate 

 that the nuggets have undergone either igne- 

 ous or hydrothermal fusion. 



It is not often that there is an opportunity 

 to determine the changes in a well water 

 extending over a long period of years, but this 

 has been done by W. W. Fisher in the case of 

 the water of the Trafalgar Square well. He 

 prints in a recent number of the Analyst an 

 analysis just made of this water, comparing 

 it with analyses made in 1848 and in 1857. 

 These analyses show that the character of the 

 water has not changed essentially, although 

 the quantity of potassium salts has diminished 

 quite decidedly. In this connection the author 

 calls attention to the fact that alkaline waters 

 are drawn not only from the chalk under the 

 London clay, but also from other deep lime- 

 stones, and draws the conclusion that the 

 alkali salts present come from the chalk itself 

 and not from percolation. In covered depos- 

 its where no natural drainage is possible, the 

 chalk is found to contain soluble salts, dis- 

 tinct traces of sodium carbonate, chlorid and 

 sulfate being found in chalk beneath London 

 at a depth of 500 and 800 feet. 



J. L. H. 



RECENT ZOOPALEOWTOLOOY. 



fritsch's 'fauna deb gaskohle und der 

 kalksteine der permformation, bomens.' 

 Dr. Antoine Fritsch, of Prag, has recently 

 issued a complete list of his publications ex-» 

 tending back to the year 1851 and covering 

 essentially the broad field of his zoological 

 and paleontological observations. His most 

 monumental work is on the primitive fishes, 

 amphibians and reptiles of the Permian pe- 

 riod described in a series of monographs un- 

 der the title cited above, beginning in the year 

 1880. 



The first monograph covers the long-bodied 

 stegocephalian amphibians of the order Aisto- 

 poda; this was continued with the description 

 of the short-bodied forms resembling the mod- 

 ern perennibranchiates in 1884. More ad- 

 vanced labyrinthodonts were described in 

 1885, the amphibian division of the fauna 

 being concluded in 1887. 



The second volume is mainly devoted to the 

 lung fishes, or Dipnoi, and to the more primi- 

 tive types of selachians. Most important of 

 these types is the genus Pleuracanthus which 

 bridges over the gap in fin-structure between 

 the American genus Cladoselache, as de- 

 scribed by Newberry and Dean, and the fin of 

 the modern shark. This transition form com- 

 pletely disestablished the archipteryial theory 

 of Gegenbaur and established the fin-fold 

 theory of Thacher and Balfour. The other 

 primitive selachians were concluded in 1893, 

 and the great modern actinopterygian types 

 corresponding to Agassiz's ganoids were cov- 

 ered in the parts which appeared during the 

 succeeding two years. 



The fourth volume, of which three parts 

 have appeared between 1899 and the present 

 time, is devoted to the insects of the Permian 

 period, especially the myriopods and arach- 

 noids. Finally, this monographic series is 

 brought to a close in 1901 by the third part of 

 the fourth volume which covers the crusta- 

 ceans and molluscs. This series of mono- 

 graphs will constitute the greatest monument 

 to its author. Also, those who visit Prag 

 find there to their surprise that this Bohemian 

 city contains one of the most beautiful zoolog- 

 ical museums in the world, developed under 

 the direction of this veteran zoologist. 



H. F. O. 



GRAVITY ON THE OCEAN. 

 The proceedings of the Academy of Sci- ■ 

 ences of Berlin of February 13, 1902, contain 

 a paper by Professor F. R. Helmert on Dr. 

 Hecker's determination of gravity oa the 

 Atlantic Ocean. In July and August, 1901, 

 the International Geodetic Association en- 

 trusted Dr. Hecker, of the Potsdam Geodetic 

 Institute, with the duty of making relative 

 gravity observations on the Atlantic Ocean on 

 a voyage between Hamburg and Bahia. The 

 method employed was to determine the pres- 

 sure of the atmosphere by means of a barome- 

 ter and a hypsometer (boiling point thermo7n- 

 eter). The barometric formula contains a 

 term depending on the intensity of gravity at 

 the place where the observation was made. 

 The hypsometer is independent of this influ- 



