580 



SCIENCE. 



[N. S. Vol. XIX. No. 484. 



stone, and the cist thus formed had been cov- 

 ered with jagged fragments of rock, over 

 which earth was spread. This doll-like carv- 

 ing of antler is considered to be one of the 

 finest pieces of prehistoric art ever found in 

 northwestern America. 



James E. Lough, 



Secretary. 



SECTION OF GEOLOGY AKD MINERALOGY. 



The Section of Geology and Mineralogy- 

 held its regular meeting January 18, 1904, 

 with the chairman. Professor James F. Kemp, 

 presiding. In the absence of the secretary, 

 Dr. A. A. Julien was appointed secretary pro 

 tern, and papers by Dr. Irving and Mr. Wil- 

 son, abstracts of which follow, were presented. 



Microscopic Structure and Origin of Certain 

 Stylolitic Structures in Limestone: J. D. 

 Irving. 



From an extended examination of stylolitic 

 limestones collected in Indiana and Wyoming, 

 mainly by Mr. M. L. Fuller and himself, the 

 author has drawn the following conclusions 

 regarding the origin of the peculiar struc- 

 tures : 



1. They were initiated along a thin clay 

 layer in limestone and have been produced by 

 the interpenetration of the limestone material 

 on either side of this clay seam. 



2. They are entirely independent of the 

 presence of fossils existing in the rock, for 

 they occur equally in those portions of the 

 rock where fossils are absent and where they 

 are present. 



3. They were not formed by metamorphic 

 agencies, or by the weight of overlying strata, 

 or by other causes which would tend to distort 

 and crush the rock material. 



4. They were produced by a cause which 

 operated on the material of the rock while it 

 was yet unconsolidated, and in a condition 

 approximating that which obtained at the time 

 of deposition. 



5. They originated under great pressure, the 

 rock material being sufficiently soft to allow 

 the bending of individual stylolites, and yet 

 potentially rigid, so that organisms were 

 sharply sheared off while held in the soft 

 matrix. 



While the cause of the pressure and the 

 manner in which it had operated to produce 

 these structures has not been determined, the 

 author suggests that their production may be 

 the result of the hydrostatic pressure of the 

 sea water lying above the deposits. In the 

 instances examined stylolites are character- 

 istic of marine deposits formed in water vary- 

 ing from 400 to 2,500 fathoms in depth. If 

 sea water be taken to have an average 

 specific gravity of 1.028, then a one-foot 

 column of water exerts a hydraulic pressure 

 of .434 lb. per sq. in. of area. This would 

 give, for the depth stated, a hydrostatic pres- 

 sure of from 1,041 to 6,408 lbs. per sq. in. 

 Such a pressure as this, coupled with the soft 

 unconsolidated nature of the rock at the time 

 it might have been exerted, seems to fulfil 

 better than any other the conditions de- 

 manded by the observed facts. 



Recent Journeys among Localities Noted for 



the Discovery of Remains of Prehistoric 



Man: J. Howard Wilson. 



The author discussed man in the earliest 

 times before the Neolithic age and afterwards 

 illustrated his paper by nearly forty views of 

 some of the most famous rock shelters, caves 

 and deposits of Europe which have furnished 

 remains of paleolithic man, including also 

 slides of the type implements and weapons 

 from which have been derived the principal 

 evidence of man's existence in Quaternary 

 times. 



The paper recited briefly the history of the 

 subject, the first finds, especially the work of 

 Boucher de Perthes, and the gradual develop- 

 ment of the science of prehistoric archeology. 

 Reference was made to some of the disputed 

 evidence of man's existence in the Tertiary 

 period, and then the subject of man's existence 

 as early as the Second Glacial period was 

 treated more at length, with a consideration 

 of the climate and physical conditions which 

 prevailed in paleolithic times. 



The paper closed with an attempt at a real- 

 ization of the great antiquity of paleolithic 

 man as shown by the immense physical and 

 geological changes which have taken place 

 since he first made his undoubted appearance. 



