188 RECORDS. 



Stimuli for the more minute changes which take place in the 

 remodeling of a small chela to form one of the large type. 



M. A. BiGELOW, 



Secretary. 



SECTION OF GEOLOGY AND MINERALOGY. 



May 1 8, 1903. 



Section met at 8:15 P. M., Professor James F. Kemp presiding. 



The minutes of the last meeting of section were read and 

 approved. 



The following program was then offered : 



George I. Finlay, The Geology of the Nephelite Sye- 

 nite Area at San Jose, Tamaulipas, Mexico. 



Fred H. Moffet, The Copper Mines of Cobre, Santiago 



DE Cuba. 



Summary of Papers. 



In his paper Dr. Finlay said in part : The town of San Jose 

 in the State of Tamaulipas, Mexico, lies in a hollow surrounded 

 on all sides by mountains, and is about seventy miles from the 

 coast of the Gulf of Mexico. The range of peaks immediately 

 to the south of it, and extending for fifteen miles in that direc- 

 tion, is of nephelite-syenite. The range is known as the San 

 Carlos Mountains. San Jose itself is on the site of an eroded 

 laccolith of andesite (locally known as " porphyry"), intruded 

 into limestone. Some limestone masses stand on end within 

 the area of the laccolith, and are thought to have floated or 

 worked their way down to their present position during the in- 

 trusion of the igneous rock. There are two or three hundred 

 of these isolated limestone masses, and it is in connection with 

 these that the copper ores are found. Contact metamorphism 

 has not been developed to any great extent in the limestone 

 surrounding the laccolith, but has been greatly induced in the 

 included masses ; marble, grossularite, vesuvianite and other 

 minerals having been produced. Aside from the occurrence of 

 the nephelite-syenite in the area south of the laccolith, the region 

 is interesting on account of the dyke rocks which are found cut- 



