716 ABSTRACTS OF PAPERS 



it has been studied is such as to warrant the conclusion that they have been 

 laid down under open water. It follows that coals containing mother of coal 

 are not derived from the transformation of peat bogs into coal, as is almost 

 universally assumed, but owe their origin to sedimentary deposits of vegetable 

 matter in open ponds or lakes. Since the presence of mother of coal in coals 

 other than cannels and boghead or oil shales is almost universal, it follows 

 that our ideas of the conditions under which coal has been formed must be 

 very radically modified. It follows also that the question of the conservation 

 of coal deposits has an added importance from the realization of the extreme 

 slowness with which they have been formed. The paper is illustrated by a 

 number of colored photomicrograms of coals of the United States, Europe, and 

 Australasia. 



POTTSVILLE-ALLEGHENY BOUNDARY IN THE INTERIOR PROVINCE 

 BY DAVID WHITE 



(Abstract) 



The Coal Measures of these States do not so frequently contain well preserved 

 plant remains as do those of the Appalachian trough, on account of the near- 

 ness of the coal-forming swamps and marshes to sealevel and the frequent 

 submergence beneath salt or brackish water when the rate of subsidence was 

 too great or protective barriers were breached, thus sometimes permitting the 

 invasion of shoal-water marine molluscan faunas over the areas of underlying 

 peat. The paleobotanic material in hand indicates early Allegheny age for 

 coal ''No. 2" (Murphysboro, Colchester, Mazon Creek coals) of Illinois, and 

 the reference of coal "Xo. 1" to the Pottsville. the associated stoneware clays 

 of the State being distinctly Upper Pottsville (probably Connoquenessing) in 

 age. On both paleobotanic and stratigraphic grounds the Bevier coal of the 

 Missouri fields is regarded as probably equivalent to coal "No. 2" of Illinois, 

 the Tebo coal, next lower in Missouri, being apparently of Upper Pottsville age. 

 In both basins the Pennsylvanian sea entered from the south, permitting the 

 deposition of earlier beds to the southward, and, toward the close of Pottsville 

 time, encroached on the old land to the. north throughout a region including 

 the greater part of the present coal-field area. In Missouri the overlap was 

 stronjrly northeastward. 



ORIGIN OF THE HARD ROCK PHOSPHATE DEPOSITS OF FLORIDA 

 BY E. H. SELLARDS 



(Abstract) 



Some of the problems to be accounted for in the origin of the hard rock 

 phosphate deposits of Florida are: (1) The source of the phosphate and of 

 the other materials of which the deposits are made up, including sands, clays, 

 flint pebbles, phosphate and flint boulders, and limestone inclusions; (2) the 

 intimate admixture in the deposits of these diverse materials; (3) the pro- 

 es by which the phosphate and flint boulders have formed; (4) the localiza- 

 tion of the workable deposits of phosphate; (5) the limitation of the hard 

 rock phosphate area to a particular and well marked physiographic type of 



