Miscellanies. 383 



glomerate made up from pebbles derived from a great variety of rocks, 



of whicli a large proportion are limestone, and the cementing earth, fre- 

 quently red and also of various colors, contains much lime mixed with 

 other materials; when polished it is beautiful, especially in large masses. 

 This rock belongs to the middle secondary, and appears to have been 

 produced along with other rocks of the same age at a period subsequent 

 to the elevation of the lower secondary, including the coal formation. 



The red sandstone formation is frequently disrupted by trap, which ri- 

 ses above it in ridges and peaks, and has frequently indurated the shales 

 and sands into a rock resembling a brick or tile. 



The strata of the anthracite coal formation evidently owe their position 

 and limits to elevation by fire, and denudation by water, which has often 

 swept away extensive masses formerly connected. 



We cannot enter upon the phenomena of the coal fields, nor upon the 

 proofs of their disturbance, which are presented by their synclinal and 

 anticlinal axes, and by innumerable indications of violent movements, as 

 by the upheaving of the strata along certain lines, and "the simultaneous 

 destruction of large portions of them by the scooping action of a mighty 

 flood. To the effects of these grand geological dynamics Prof Rogers 



will himself do justice in his final report. 



The geological statistics of our surveys are now swelling annually into 

 a vast magazine of materials entirely incompatible with the limits of a 

 journal of science even to sketch, but affording to local interests a happy 

 guide, and an encouraging excitement, while science will in the end vin- 

 dicate her claims by drawing those conclusions which are the safer, and 

 the more important as they are built upon a wider induction from facts well 

 observed and faithfully described. 



54 Dr. Harems new Eudiometer, — At a conversation meeting of the 

 Franklin Institute of Philadelphia, held May 23d, 1839, Dr. Hare ex- 

 hibited an improved aqueous, sliding-rod, hydro-oxygen Eudiometer, 

 and stated that this instrument enabled him to analyze the air accu- 

 rately within thirty seconds. Being, however, made to be used with 

 water, accurate results could not be obtained by it when carbonic acid 

 was one of the products, of which an accurate measurement would be 

 necessary. It would of course be impossible to ascertain how far an 

 absorption of this gas by water might add to the absorption resulting 

 from the combustion and consequent condensation of hydrogen. 



fji 



another eudioraetrical 



instrument Ij^-j , been constructed many years ago, in which mercury 

 was the conli.iing liquid. The mercurial sliding-rod eudiometer, now 

 laid before the Institute, was an improved modification of that instru- 

 ment. The pressure within the receiver of the apparatus in question 

 being varied, (by pushing in or pulling out the rod through a collet 



