Lo 
250 Address before the Association of American Ge 
which are six thousand two hundred and thirty four feet high ; 
although the nature of the rock there, is most unfavorable for — 
preserving furrows and markings. 
Thirdly, the smoothing and furrowing of the rocks oxhibine 
almost equal freshness at all altitudes, which antares an ap- 
proach to synchronism in the producing cause. 
Fourthly, the almost perfect parallelism presetvedl cop the 
grooves and scratches over wide regions, shows that they were 
made by the projecting angles of very large and heavy masses of 
great extent, moving over the surface with almost. irresistible 
force, by water or some other mighty agent. There is sometimes 
more than one set of scratches, which intersect one another at a 
small angle, as has been shown by Prof. Locke to occur in Ohio, 
but each set preserves its parallelism most perfectly. Even where 
they pass over high and precipitous mgr; they are ais ane 
out of their course. 
Fifthly, this agency ippduts to have been less and less aide 
ful as we go southerly. We have as yet, indeed, had but few 
trusty reports on this subject from the southern portionsisf North 
America ; but had the phenomena of drift been as striking there 
as in New England, New York and Canada, they would certainly, 
ere this, have been described. It ought not to be forgotten, how- 
ever, that De la Beche: hhas described the drift of, Jamaica 2 oti 
similar to that of New - ! 
Sixthly, the relative ievels of. ae sata snes not oan’ escent 
tially changed by vertical movements, since the epoch in whieh 
this agency was exerted. They could not have been much 
ed without disturbing the detritus, often fancifully arranged 
in'the valleys and on the flanks of the hills; nor without some- 
times breaking up the smoothed and furrowed surfaces of the 
rocks along their joints or planes of stratification. . But such @ 
disturbance I have never witnessed. _ 
Seventhly, the North American coritinent must have pa 
essentially, » its present height above the ocean, previous to the ex- . 
ertion of th gency. r all our formati , as high at. least as 
the eocene tertiary, are-covered. swith drift ; and I know of no ev- 
idence of any important uplift subsequent to that which has tilted 
Up our tertiary strata, oP oe Re could not pment 
pee icon ai af. — a th A ee ae a 
he as ed 43 a oe ee eee ee 
> eaQuUuUC! MA Line pee i 
se ein Pe Ce ae 
ro . &, : oe ee “ 
ee ee 
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