REPORT OF THE SECRETARY. 75 



tbo Naval Observatory. It was determined that the only jnacticable 

 scheme -would be to rely upon the voluntary and unpaid co operation of 

 individual observers and upou the aid which niiglit be gained from 

 the assistants of the Signal Service and other Government bureaus 

 having permanent stations scattered throughout the country. Mr. C. 

 F. Marvin, of the Signal Service, undertook to devise an jnstrument, 

 inexpensive and simple, and requiring a niiuimuni of care and atten- 

 tion, which could be used by volunteers m making their observations. 

 Numerous responses have been received to the circulars that were sent 

 out asking for assistance in this work. 



Potomac Division of Geology. — Mr. W J McGee continued his geo- 

 logic investigation of the District of Columbia and contiguous territory 

 as the condition of the topographic survey of the area under discussion 

 permitted. He gave special attention to the Potomac formation, both 

 as disclosed in the District of Columbia and elsewhere, and, in the ab- 

 sence of fossil faunas characterizing the formation, he availed himself of 

 the assistance of Professors Ward and Fontaine in reaching some con- 

 clusions as to its taxonomy through a study of its fossil flora. A large 

 amount of miscellaneous office work is intrusted to the chief of this di- 

 visiou, and the most important subjects of this character which have en- 

 gaged his attention during the period under review are briefly referred 

 to below. Mr. McGee continued to assist the Director in developing a 

 cartographic system, which, while sufficiently comi)rehensive to repre- 

 sent the rock masses in the entire dominion of the United States, is at 

 the same time sufficiently definite to be intelligible to all users of the 

 geologic maps published by the Survey and sufficiently elastic to per- 

 mit the employment of classifications of rocks now in vogue or such as 

 may be hereafter evolved. The work has led to the preparation of a 

 bulletin entitled "A Contribution to the Areal Geology of the United 

 States," which is now nearly ready for the press. A meeting of the 

 Congres Geologique International was held at Berlin in September and 

 October, 1885, and Mr. McGee represented the Director of the Survey in 

 its deliberations, presenting to it a formal communication on his behalf. 

 The principal function of this Congress, which was organized largely 

 through the instrumentality of American geologists, is the improve- 

 ment and unification of conventions employed in geologic cartography. 

 Under Mr. McGee's direction a bibliography of the geology of Texas 

 has been prepared and is nearly ready to send to the press. The Sur- 

 vey having undertaken to compile a history of American State surveys, 

 from data contributed as far as possible by those who have engaged in 

 the work, the material has been placed in Mr. McGee^s hands, and a 

 manuscript history of American State surveys is now substantially com- 

 plete. To the gentlemen who have generously turned aside from other 

 duties and interests and prepared material for this proposed history, 

 the profound obligations of the Survey are warmly extended. 



