ABSTRACTS OF PAPERS 81 



which tlie public looks for standards, done for the promotion of land relief 

 work? How much notable work dignifies and illuminates American geology 

 in our National Museum? Other institutions have fortunately proven l)y con- 

 crete example that nothing else is so capable of arousing as large an interest 

 in earth science as the naturalistic relief. 



As land reproduction in relief is one of the most inclusive sulijects in the 

 earth sciences, it is. old opinion notwithstanding, one of the larger sul)jects 

 in geology and geography, and it is pertinent to note that some geologists now 

 iire beginning to see more clearly their great opportunity long overlooked. 

 This insight should lead to a demand for more dignified work and help to 

 change conditions (indirectly responsible for the large amount of unsatisfac- 

 tory work in our museums, institutions, and expositions) whicli have made 

 it practically impossible to do good work in this subject in our government 

 bureaus. It may help to pave the way for geology to develop and utilize one 

 of its best assets. 



Presented l)y iillo in the absence of tlie author. 

 Section adjourned al 5 o'clock p. m. 



SECOND SECTION 



The Second Section did not convene on the afternoon of the first day 

 on account of the desire felt by its members to participate in the meeting 

 of the Paleontological Society. 



TITLES AND ABSTRACTS OF PAPERS PRESENTED BEFORE THE THIIJD SECTION 



AND DISCUSSIONS THEREON 



The Third Section convened about 3.35 o'clock p. ni., with IT. P. dish- 

 ing in the chair and Ernest Howe serving as secretary. The section took 

 up the reading of papers in Group C as follows : Petrologic, Mineralogic, 

 and Economic. 



PRE-CAMBlilAN IGNEOUS ROCKS OF THE PENNSYLVANIA PIEDMONT ^ 



BY F. nASCOM 



(Abstract) 



Pre-Cambrian igneous rocks of the Pennsylvania Piedmont are pegmatite, 

 rhyolite, granite (granltite, hornblende granitite. hornblende granite), grano- 

 dioritp, quartz diorite, andesite. quartz norite. quartz gabbro. gabbro (norite. 

 augite gabbro, anorthosite, hornblende gabbro), basalt, pyroxenite (webstcr- 

 ite), and peridotite. 



The application to lliem of the quantitative .system of classification shows 

 (rt) that the.v form :i rcui.iik.iljly cnntiinKnis scries from ;i pors.ilic to ;i jicr- 



* By prrmi.ssioii nf (hi> I liicdor nf (ho I'. S. Geological Siirvry. 



