REPORT ON THE DEPARTMENT OF LITHOLOGY AND PHYSICAL GEOLOGY 

 IN THE I". S. NATIONAL MUSEUM. 1889. 



By George P. Merrill. Curator. 



So far as is to be judged from the mere acquisition of materials, the 

 year just closed has been one of unprecedented activity and progress 

 in this department. This may be accounted lor by the fact that (1) the 

 Curator has been enabled to visit in person sundry localities and obtain 

 thence desirable materials, and that (2) the department having become 

 fairly established and with a fair amount of duplicate material, we have 

 been enabled to make a series of profitable exchanges. The U. S. 

 Geological Survey has also furnished much valuable matter, as will 

 be noted later. 



On July 17 the Curator left on a collecting trip into southwestern 

 North Carolina, returning on the 20th. The main points visited were 

 Webster, Jackson County, and the corundum mines at Cullasaja, 

 MacoD County. Prom these localities were obtained several hundred 

 pounds of necessary material, consisting chielly of rocks of the peridotite 

 and pyroxenite groups. On August 4 a second trip was made into Penn- 

 sylvania, followed during the summer vacation by excursions into 

 northern New York, Vermont, New Hampshire, eastern Massachusetts, 

 and as far east as Hast port, Maine. 



The material collected during these trips will be noted under the 

 head of neeessions, but mention may be made here of a line series of 

 slates from Lehigh and Northampton Counties, which were selected 

 with a view to illustrating the efficacy of pressure in the production 

 of slaty cleavage. Blocks were obtained, showing very plainly the emi- 

 nent cleavage at a sharp angle wit h t he bedding, and also blocks which 

 through lack of homogeneity in various layers, yielded unequally to the 

 compressive force, the finer grained and more uniform portions becom- 

 ing evenly and finely fissile, while the coarser layers were crimped, 

 crushed, or repeatedly faulted in a very instinctive manner. 



A series of photographs was also obtained to illustrate certain physi- 

 cal phenomena, such as could not be illustrated by means of speci- 

 mens. 



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