December 2, 1904.] 



SCIENCE. 



761 



Triassic beds may be more properly consid- 

 ered as of contemporaneous formation with 

 the enclosing beds, or whether they are later 

 concentrations or may have been brought in 

 from some entirely foreign source. 



Dilation Fissures and Their Contained Ores. 



Mr. W. H. Weed. 



Dilation fissures are the fractures formed 

 by expansion or dilation of a rock mass, as 

 in the alteration of peridotite or other basic 

 rocks to serpentine, a change involving an in- 

 crease of volume of 20 to 33 per cent. The 

 resulting rook is checked by minor fissures, 

 and often accompanied by crushed areas and 

 by larger fractures with persistent course, 

 slickensided walls and polished balls and 

 shelly serpentine. The lesser fractures ex- 

 tend to relatively shallow depths. The larger 

 are trunk channels for circulating waters. 

 Serpentinization . appears to be due to deep- 

 seated ascending waters. Chromite, various 

 nickel ores, and in Italy and Cuba, copper 

 ores (chalcopyrite and pyrrhotite) known to 

 exist in small quantity in the unaltered rock, 

 are presumably dissolved by serpentinization 

 processes and deposited by filling and replace- 

 ment along the fissures and crushed masses, 

 forming ore deposits. 



Evidence of Caves of Put-in-Bay, Ohio, on 

 Question of Land Tilting. Mr. M. L. 

 Fuller. 



The caves of Put-in-Bay have been long 

 known to the public, but, with the exception 

 of Mr. E. L. Mosely, no one seems to have 

 discussed the evidences which they present 

 as to recent changes of lake level. Daussa's 

 Cave is probably the one which Mosely vis- 

 ited. In this cave there is an underground 

 lake 80 feet long and 40 feet wide, which is 

 connected with and fluctuates with the waters 

 of Lake Erie. The water is several feet deep 

 and on the bottom may be seen a number of 

 stalagmites, mostly broken and discolored as 

 if of considerable age. These submerged sta- 

 lagmites, which are of open air formation, 

 indicate a rise of the lake water level rela- 

 tive to the land. Three other caves. Perry, 

 Crystal and Paradise were visited during the 

 past summer. Perry Cave is a solution cav- 



ern, notable for its broad, low arch, 200 feet 

 or more in diameter, and 5 to 7 feet high. 

 Crystal Cave is an immense geode, 10 to 15 

 feet in diameter, lined with crystals of celes- 

 tite up to a foot or more across. Neither of 

 the caves throw much, if any, light on the 

 problems of change of level. In Paradise 

 Cave, however, which has been only recently 

 opened, the stalactites are still preserved and 

 afford more definite evidences. In this cave 

 the stalactites, which are still dripping, are 

 pendant from a sloping roof which dips be- 

 neath the surface of an underground lake con- 

 nected with Lake Erie. There is no break in 

 the stalactitic group between the portions 

 above and below water level, indicating them 

 to be essentially contemporaneous. The fact 

 that those beneath the water level are prac- 

 tically as long as those above would indicate 

 that the submergence was of so recent date 

 that no material addition has taken place to 

 those in the open air since the change of level. 

 The submergence of the stalactites simply in- 

 dicates a change of level of the lake waters rel- 

 ative to the land and does not in itself afford 

 positive evidence of tilting. The oceurtence 

 of submerged tree stumps and other accordant 

 evidences, all testifying to a similar change 

 of level, seem to point to the tilting move- 

 ment, established by Gilbert as a little less 

 than half a foot to a hundred miles per cen- 

 tury, as the cause of the submergence indi- 

 cated by the stalactites of the caves. 



Geo. Otis Smith, 

 Secretary. 



BIOLOGICAL SOCIETY OP WASHINGTON. 



The 389th regular meeting of the society 

 was held on Saturday evening, October 22, 

 1904. The following communications were 

 presented : 



The Insect-Catching Grass of Cuha. E. A. 



SCHWARZ. 



With the beginning of the rains in Cuba, 

 countless swarms of insects appear. At this 

 time also, a grass becomes common, which 

 catches multitudes of the insects in its flower- 

 ing spikes. They are caught day and night, 

 and in incredible numbers. 



The spiny involucre of the spikelets of the 



