8 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



limestone conglomerate were obtained with little difficulty, but 

 equally good examples of the siliceous variety were secured only 

 after much hard labor, owing to the ready disintegration of the rock 

 on exposure. Efforts were finally successful, however, and there was 

 also secured a mass of the so-called " edgewise " conglomerate several 

 feet in diameter, which will well illustrate the phenomenon of intra- 

 formation conglomerate described by me a number of years ago. 

 This last was obtained where the steeply dipping lower Ordovician 

 beds outcropped in such a manner that the desired material could be 

 blasted without fracturing. All of such conglomerates are the result 

 of ancient mud deposits of tidal flats becoming sun cracked when 

 exposed to the air. The dried edges of the sun-cracked areas become 

 tossed about by the wind and the fragments finally accumulate in 

 layers which ultimately are hardened into rocklike conglomerate. 

 Conglomerates usually indicate the base of a formation, but this 

 particular kind may occur at any place within a formation, whence 

 I applied the specific name " intraformational " to them. 



GEOLOGICAL WORK IN CENTRAL KENTUCKY. 



After the conclusion of geologic work in the Appalachian Valley in 

 the early summer of 1917, Dr. Bassler proceeded to central Kentucky, 

 where he spent several weeks in explorations for suitable exhibition 

 specimens covering the general subject of stratigraphic paleontology. 

 It was especially desirable that such phenomena as stratification, the 

 occurrence of fossils, and unconformities should be illustrated in the 

 Museum, and especial efforts were made to secure specimens exhibit- 

 ing these features. Much discrimination was necessary in the selec- 

 tion of these objects, as it was essential to obtain specimens of such 

 size as to be appreciated by the public and still not too large for the 

 available space, which is somewhat limited. This difficulty compli- 

 cated the work, but the selection finally made was extremely satisfac- 

 tory. In his account of the work Dr. Bassler says : 



The early Paleozoic coral reef near Louisville, Ky., from which a section 

 6 by 10 feet in dimensions had been quarried and placed on exhibition during 

 the summer of 1916, was revisited and several additional layers of highly fos- 

 siliferous shale and limestone were secured. These have now been added in 

 their proper position to the coral-reef mount, so that this single exhibit now 

 illustrates the subjects of stratification in general, horizontal strata, change of 

 lithology from limestone to shale, the occurrence of fossils in these types of sedi- 

 ment, and the phenomenon of fossil coral reefs for which the exhibit was pri- 

 marily planned. 



The most valuable result of the summer's work was achieved at El kin, Ky. 

 Here a single limestone slab, 6 feet long and several feet wide and thick, show- 

 ing an unconformity distinct enough to be appreciated by the layman, was 

 quarried out and shipped to the museum without breakage, where it now forms 

 a most instructive exhibit. The outcropping limestone ledge, several feet in 

 thickness, is composed of a distinctly white lower portion and a dark-colored 



