March 2, 1883. 



SCIENCE. 



109 



the study of south-east Pennsylvania) are associated 

 with distinctively chlorite schists, are in contact with 

 the orthofelsite of the South Mountain, in Adams 

 and York counties, Penn. Very similar schists may 

 also be met (tliougU in this case without the pres- 

 ence of orthofelsite) in the Chestnut-hill ore-banks, 

 just north of the town of Columbia, on the lower 

 Susquehanna, and in the Grubb ore-bank, Hellam 

 township, York county. Parts of these rocks in 

 Porth Ceri are very hard, and resemble strikingly 

 some of the greenish grits on the left bank of the 

 Susquehanna, near the Maryland line. These beds 

 on their exposed surfaces become more and more dis- 

 tinct from each other in color as their disintegration 

 proceeds; and it is impossible to overlook the anal- 

 ogies which even these physical features present to 

 the variegated clays, chiefly red and white and pink, 

 which border the bases of the South Mountain, both 

 on the east and in the Cumberland Valley, in Penn- 

 sylvania. Another paragenesis, strikingly analogous 

 to that in the South Mountain, is found at Trelethyn, 

 about one mile west by north of St. David's, near 

 one of the largest bands of ' greenstone,' which are 

 colored as such on the geological map. Here is a 

 hard, silicious, greenish rook, with interstitial spaces, 

 filled with milk quartz and epidote, the latter in large 

 excess. This mixed rock, as is the case very fre- 

 quently in Pennsylvania, forms low ridges in the 

 midst of the softer chloritic schists and orthofelsites, 

 with which it is almost always closely associated. 

 About a mile west by south of St. David's is a hum- 

 mock, pronounced to be a porphyritic lava, and which 

 greatly resembles the hard green silicious rock, which 

 occurs near Williamson's Point, on the left bank of 

 the lower Susquehanna, near the Maryland line. It 

 is a very important point in the proper understand- 

 ing of the structure here, and its analogy with the 

 Appalachian phenomena, to determine whether the 

 band of schists which intervene between the two 

 belts of intrusive beds be really Cambrian, or 

 whether they may not correspond with the horizon, 

 to which Dr. Hunt and the writer have supposed that 

 the enormous masses of crystalline schists which 

 stretch from "Vermont to Georgia belong. On this 

 point the writer feels unwilling to differ with the able 

 geologists who have assigned their position to the 

 English schists, without attaining, at least, to a por- 

 tion of their information and experience of this 

 terrain. It is certain that if they be in reality Cam- 

 brian, there are great difficulties in the way of con- 

 sidering the orthofelsite beds to the north-west as 

 forming a part of the Huronian. Dr. Frazer studied 

 carefully the structure, with especial reference to the 

 mooted questions connected with the age of the syen- 

 itic granite passing through St. David's; and from the 

 appearances of injection of syenitic matter into 

 the elastic beds of the Cambrian shales, regarded 

 the conclusion as unavoidable, that the whole of the 

 syenitic granite mass, of which a part forms the 

 foundation of south-eastern St. David's, is younger 

 than the schists which lie to the south-east of it. If 

 this be so, there is good reason for ascribing the 

 rocks to the north-west of this granite belt to the 

 same age, and of explaining their somewhat modified 

 litbological characters to the alteration produced by 

 this large igneous mass. In summing up his im- 

 pressions. Dr. Fr.azer said, — 



1. There is a striking analogy between some of the 

 beds which constitute the lower Cambrian in South 

 Wales, and some of the beds which constitute the 

 horizons proximate (both above and below) to the" 

 primal of Rogers, or the Potsdam of the New- York 

 geologists. These analogies are not confined to kinds 



of rocks, but embrace paragenesis, topography, and 

 accessory mineral contents. 



2. There is a strking analogy between the orthofel- 

 sites, ash-beds, syenitic granites, diabases which here 

 seem to be younger than the above, and the same 

 rocks which in the Appalachian region of America 

 seem to be older than the primal. 



According to the current views of the English geol- 

 ogists, the entire coast-line, which forms the sub- 

 ject of these notes, is minced up by faults of differ- 

 ent extents and directions. The writer was not able 

 to convince himself of the existence of all of these 

 faults, nor has he ever seen so many together. At 

 the same time he does not wish to compare on equal 

 terms the experience gained in his short visit with 

 the greater experience of his hosts. Still, he cannot 

 accept the view of so many faults; and mainly on 

 this account he believes the study of the structure in 

 South Wales to be especially important to American 

 geologists, although it seems to support a view of the 

 age of orthofelsites and crystalline rocks in South 

 Wales which the author has always combated, and 

 still combats, as inapplicable to the eastern United 

 States. If, however, there were a network of faults, 

 such as has been stated, the attempts to present a 

 theory of superposition would be attended with the 

 greatest difiiculties, and, with no more investigation 

 than he has had opportunity to make, would be 

 entirely fruitless. ' 



The business meeting. 

 Dr. Thomas M. Drown, the secretary, presented the 

 report of the council, from which it appeared that 

 the receipts of the institute for the year had been 

 $13,169.05, and the expenses $8,140.53; leaving a bal- 

 ance of $5,028.52, which will be invested by the 

 council. The receipts were much higher than in the 

 previous year, the result of a large increase in mem- 

 bership. The tenth volume of the proceedings has 

 been issued, and there will soon be published an in- 

 dex of all the volumes thus far published. Regular 

 meetings were held at Washington and Denver, at 

 which it was gratifying to note the large increase 

 of papers on the mining and treatment of the ores of 

 the precious metals. Daring the year 10 members 

 have resigned, 25 have been dropped for non-payment 

 of dues, and 8 have died, leaving the present mem- 

 bership at 1,213; of these, 5 are honorary, 50 foreign, 

 and 149 associate members. 



The following-named gentlemen were elected officers 

 for the ensuing year: president, Robert W. Hunt, 

 Troy, N. Y. ; vice-presidents (for two years), S. F. Em- 

 mons, Denver, Col.; W. C. Kerr, Washington, D.C. ; 

 S. T. Wellman, Cleveland, O. ; managers (for three 

 years), John Birkinbine, Philadelpiiia, Penn. ; Stuart 

 M. Buck, Coalburgh, Kanawha County, W. Va. ; E. 

 S. Moffat, Scranton, Penn.; treasurer, Theodore D. 

 Rand, Philadelphia; secretary, Thomas M. Drown, 

 Easton, Penn. 



The following papers were read by title only: Gas- 

 producer explosions, by P. Barnes, Elgin, 111. ; Ice 

 mining and storing, by Prof. W. P. Blake, New Haven, 

 Conn."; The mining region about Prescott, Arizona, 

 by John F. Blandy, Prescott; Blast-furnace practice, 

 by Casimir Constable, New York, N.Y. ; Notes on 

 the geology of Egypt, with especial reference to the 

 rocks from which the obelisks have been taken, by 

 Dr. Persifor Frazer of Philadelphia, Penn. ; Notes on 

 a protected iron hot-blast stove, by Frank Firmstone, 

 Easton, Penn. ; The geology of Cape Hatteras and 

 f> the south Atlantic coast, by Prof. W. C. Kerr, Wash- 

 "Mugton, D.C; The divining-rod, by Dr. R. W. Ray- 

 mond, New York, N.Y. ; Notes on the Linkenbach 



