March 10, I'JOo.j 



SCIENCE. 



891 



land wliere there were no competitors, while 

 the Haitian and Cuban forms from which 

 they sprang have been kept true to type by 

 the competition of the rest of the fauna by 

 which they are surrounded. If there were 

 any way of determining approximately the 

 time which has elapsed since the elevation of 

 the Bahamas above the sea in the Pleistocene 

 epoch, we should have a means of determining 

 the rate at which evolution and specific differ- 

 entiation may proceed in such an assemblage 

 of pulmonate mollusks placed in a suitable 

 environment and not subjected to serious com- 

 petition. 



Pre-Camhrian Rocks of the Franklin Furnace 

 Quadrangle : Mr. A. C. Spencer. 

 The view held by Rodgers, Cooke and Brit- 

 ton that the gneisses of the New Jersey High- 

 lands are mainly metamorphosed sediments, 

 has not been seriously challenged up to the 

 present time, though two of the more recent 

 investigators of the field (Nason in 1890 and 

 Wolff in 1896) have left the way open for 

 accepting an igneous origin for these banded 

 feldspathic rocks. Field work in the vicinity 

 of Franklin Furnace carried on during the 

 summer of 1904 warrants the conclusion that, 

 so far as tliis particular field is concerned, the 

 only sediments are the white limestone and a 

 few patches of quartzite, the several types of 

 gneiss being undoubtedly igneous and in large 

 part demonstrably intrusive. For the purpose 

 of the geologic map five divisions of the pre- 

 Cambrian rocks will be recognized: (1) the 

 Franklin white limestone; (2) a complex of 

 diorites and granites showing more or less 

 gneissic structure; (3) black hornblende or 

 pyroxene gneiss ; (4) white granite gneiss, and 

 (5) coarse granite or pegmatite. 



Age relations have been established as fol- 

 lows : The pegmatites cut all the other rocks ; 

 the white gneiss cuts (2) and (3) ; the black 

 gneiss cuts (1) and both phases of (2) ; and 

 finally the granite phase of (2) cuts the lime- 

 stone (1). The relation of the diorite phase 

 of (2) to the limestone has not been observed. 



Consanguinity in the Eruptive Bocks of 

 Cripple Creek: Mr. L. C. Graton. 

 Mr. Graton showed that three magma tic 



groups may be distinguished, of which the 

 most important is the series of rocks from the 

 Cripple Creek volcano. All the rocks of this 

 group possess certain characteristics in com- 

 mon and are of particular interest in having 

 a constant ratio of silica to alumina — a proof 

 of their derivation from a single magma. By 

 making certain assumptions based on the field 

 observations, the relative volumes of these 

 rocks were computed, and by that means an 

 analysis was obtained which was considered 

 to approximate the composition of the total 

 product from the magma reservoir, i. e., the 

 average rock of the Cripple Creek volcano. 



The Big Sink on the Lucin Route across 

 Great Salt Lake: Mr. J. M. Boutwell. 

 Mr. Boutwell described the construction of 

 the long trestle extending across Great Salt 

 Lake, and presented observations which have 

 an important bearing on the question of the 

 character and depth of the intermontane rock 

 basins beneath the Pleistocene sediments. The 

 author will later communicate a more com- 

 plete statement to Science. 



Geo. Otis Smith, 



Secretary. 



the science club of northwestern univer- 

 sity. 



The Science Club of Northwestern Univer- 

 sity held its regular monthly meeting in the 

 physical lecture room of Science Hall, on 

 Friday evening, February 3, 1905, at 1 :30 p.m. 

 Papers were presented by J. W. Goldwait on 

 ' Post-glacial Land Movements in New Eng- 

 land,' and by Professor U. S. Grant on ' Re- 

 cent Contributions to Metamorphism.' 



Floyd Field, 

 Secretary. 



DISCUSSION AND CORRESPONDENCE. 



A NEMATODE DISEASE OF GRASSES. 



In Europe there have been known for many 

 years certain diseases of grasses, including 

 wheat, caused by nematodes, which penetrate, 

 in the larval state, the ovaries of the flowers 

 and there reach maturity and lay their eggs. 

 The resulting larv£e reach a certain degree of 

 development and then, with the drying up of 



