Known as the Early Journal Content, this set of works include research articles, news, letters, and other writings published in more than 200 of the oldest leading academic journals. The works date from the mid--seventeenth to the early twentieth centuries. We encourage people to read and share the Early Journal Content openly and to tell others that this resource exists. People may post this content online or redistribute in any way for non--commercial purposes. Read more about Early Journal

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... ntent at http://about.jstor.org/participate--jstor/individuals/early-journal--content. JSTOR is a digital library of academic journals, books, and primary source objects. JSTOR helps people discover, use, and build upon a wide range of content through a powerful research and teaching platform, and preserves this content for future generations. JSTOR is part of ITHAKA, a not--for--profit organization that also includes Ithaka S+R and Portico. For more information about JSTOR, please contact support@jstor.org. 226 PROCEEDINGS OF THE ACADEMY OF [1880. and west from eaclh otuher, the strike of which was, wherever observable, more N. E. an(d S. Mr. than the line joining them, thus agreeing in structure with what Prof. Rogers states of the trap dykes north of the serpentine in Chester County. He also called attention to the existence of two trap dykes or two branches of that extending through the Gulf Valley, and to curious markings in quartz rock in the vicinity, suggestive of fossils in a formation r egarded as azoic. JUNE 8.