362 MESOZOK' FLORAS OF rXITKD STAFFS. 



During October. 1886, I made some furthoi' coUoctions of fossil 

 plants from tho Potomac beds at Federal Hill, in Baltimore. Professor 

 Uhler also made collections there ai\d all the new material was sent to 

 Professor Fontaine. 



The large amount of silicified wood and lignite occurring in the 

 Potomac formation made it desii'able to have it studied and determined so 

 far as its structure would permit. Di'. F. H. Knowlton undertook this 

 work in the fall of 1886, but was prevented by imperfect facilities from 

 making as rapid progress as was desirable. 



Mr. McGee, having been called upon by the health officer of the 

 District of Columljia for some notes on the geology with reference to the 

 ciuality of the subterranean waters, contributed a short paper, which was 

 embodied in the report of that officer for the year 1884-85." It was in 

 this paper (p. 20) that the name "Potomac formation," which had been 

 in general use by the geologists of the Survey, was first published. 



Dr. F. H. Knowlton, who had ])een at work for nearly a year on the 

 fossil wood and the lignite.s of the Potomac formation, completed his 

 paper on that subject in June, 1887, and it was fonvarded for publication 

 by the Geological Survey on the 18th of that month. The publication was 

 delayed and it did not appear till 1889. '' Four new species of Cupressinoxy- 

 lon (=Sequoia) and one of Araucarioxylon w^ere systematically treated. 

 The last named, however, was afterwards found to have come from the 

 Trias. -^ 



During the year 1886 and the first half of 1887 Professor Fontaine was 

 engaged all the time he could find outside of his professional duties in 

 describing and figuring the plants of the Potomac formation, of which he 

 now had in hand an immense number. During all this time we kept up 

 a correspondence, w^ith intercliange of specimens, books, etc., and he sent 

 on lists of the names proposed for new species to be compared with the 

 literature, which I had at that time so organized that it \vas easy to prevent 

 the duplication of names. On July 1, 1887, the manuscript and drawings 

 for the monograph were forwarded by him to the U. S. Geological Survey- 



« Report of the Health Officer of the District of Columbia'for the year ending June 30, 1885, Washington, 

 1S86, pp. 19-21. 



ft Fossil wood and lignite of the Potomac formation, liy Fiaiik Hall Knowlton: Bull. U. S. Gcol. Surv. 

 No. 56, 1889, 8°, 72 pp., 7 plates. 



■•Sec Twentieth Ann. Rep. U. S. Geol. Surv., Pt. 11, 1900, pp. 264, 273. 



