3-36 Correspondence — Prof. T. G. Bonney. 



tlie north-east of it, is an unbroken sheet of Drift, with the usual 

 aspect of Till, with loose boulders, stride on exposed outcrops, drift 

 dams, buried valleys, reversed drainage, and innumerable drift 

 inclosed ponds and lakes, the elevations of which above tide are 

 given by Mr. White in his report ; the lower ones like Nichecrouk 

 and Silver Lakes, 1150' and 1250'; the higher ones like Lakes Belle 

 and Ernest 1750', Lake Laura 1800', Ellch's Pond 1754'. 



In Mr. White's Eeport, G 5 (1881) on Wayne and Susquehanna 

 counties, lying next the New "i'ork State line, similar descriptions 

 and tables of elevations of sfriee, drift ponds, etc., are given ; and the 

 exact uppermost limit of ice action is there to be seen, on the sides 

 of isolated peaks. The highest striee on Mount Ararat being 2200' 

 above tide. The elevation of the whole region may be gathered 

 from the fact that the lowest summit that the Jefferson Branch Rail- 

 way could find for its grade is 2023' A.T, Hundreds of morainio 

 ponds and lakes dot the whole map. 



I hope to put to press shortly the special report of Prof. H. C. 

 Lewis, whom I directed to trace and study the terminal moraine 

 throughout its whole line, a distance of about 450 miles, i.e. from 

 where it crosses the Delaware and enters our State from New Jersey, 

 near the Water Gap, to where it leaves the State to enter Ohio west 

 of Pittsburgh. In this repoi't Mr. Lewis maps the moraine as 

 ascending and descending our mountain sides, crossing narrow and 

 wide valleys, ascending the Alleghany mountain plateau and 

 traversing the highest lands in Northern Pennsylvania, 



The report of Mr. Ashburner on McKean county, and that of Mr. 

 Carll on the Oil Kegions, treat largely of our high-level drift and 

 the astonishing changes it has effected in our topography. There is, 

 therefore, no lack of data for Mr. Mackintosh to use ; data, be it said 

 moreover, of the most precise and complete kind. 



1008, Clinton Street, Philadelphia. J- P. LESLEY. 



THE SO-CALLED HYPEESTHENITE OF CAREOCK FELL. 



Stk, — I can fully confirm Dr. Trechmann's statement as to the 

 absence of hypersthene from the Carrock Fell rock. Some few 

 years since, feeling suspicious, I had a slide cut from one of two or 

 three specimens in my collection, and saw at once that the mineral 

 was only a form of pyroxene. The hornblende, I conjecture, is of 

 secondary formation, i.e. more or less uralite — a change especially 

 frequent in gabbros. As regards the late Mr. Clifton Ward's iden- 

 tification, I have always suspected that he had identified the Carrock 

 Fell mineral with hypersthene by its general appearance (which 

 however is not very characteristic), and not by optical tests. His 

 analysis, with its small quantity of magnesia, shows the improbability 

 of the mineral being hypersthene. Indeed, I doubt whether the 

 mineral has yet been really identified in Britain. Certainly, as 

 Zirkel has shown, and as Prof. W. H. Miller informed me more 

 than ten years since, the ordinary mineral in the Skye hypersthenite 

 is pyroxene. One or two instances have been quoted from Wales, 

 but I do not credit them. T. G. Bonnet. 



23, Denning Eoad, Hampstead. 



