September 21, 18S3.] 



SCIENCE. 



391 



found everywhere beneath the soil, each fresh 

 exposure of the rocks bringing them to light. 

 This was said years ago ; and the conviction 

 of its truth has been gaining force with evcr^' 

 year of additional observation. 



a. In view of this lact, it is urged rightly 

 that only an alirading agent that pressed 

 heavily against the broad rocky surface could 

 have produced the elfccts ; and such is not an 

 occasionally grounding iceberg, or a succes- 

 sion of them. Neither is it the still more 

 locally acting sliore-ice. 



b. Floating ice would have found little bare 

 rock over the sea-bottom to be abraded. Like 

 the bottom of existing seas, and eminently 

 those of the continental borders, the sul)- 

 morged region would have had for the most 

 ])art a bottom of detritus, its former detritus, 

 and additional detritus from later depositions. 

 The removals would have been local, and rela- 

 tively of small area. Consequently, tiie drift- 

 ing ice would rarely have reached down to the 

 rocks. .Shore-ice carried along Ijv the cur- 

 rents would have had a better chance, and yet 

 a poor one, for the work to be done. 



c. Tlie character of the groovings and 

 ploughings is, to a great extent, such as float- 

 ing ice could not have produced. As has been 

 often said, the close uniformity of direction 

 and ])arallelism over large areas, which so 

 generally prevails, is not a possible result of 

 icebei'g action. The needed pressure and 

 steadiness of movement arc wanting. Troughs 

 in hard granite even six inches deep are the 

 work of one and the same moving tool for a 

 long period ; and one year woukl be long for 

 the steady action of an icelierg. If grounded, 

 it would do almost nothing; if floating free, 

 absolutely nothing ; and a nice adjustment to 

 depth would be required for an}' steady abra- 

 sion, much nicer than would have long con- 

 tinued an\-where over the uneven bottom. 



In the triassic sandstone of Kast Haven, 

 Conn, (just east of New Haven), at a place 

 where the sandstone is a very firm, thick- 

 bedded, gritty rock, the ploughing ice ploughed 

 out a piece of moulding, somewhat like the 

 ogee of the carpenter, which was K feet deep. 

 '2') feet wide, and over l.'jO feet long, and 

 lierfectly even in surface as well as direction. 



d. The currents that would have borne along 

 the ieeljergs over submerged New England, in 

 ca.se of a submergence sufficient to cover tiie 

 highest striated surfaces, — 3,000 to 5,500 feet, 

 — would have Ijecn those of the present ocean, 

 the Labrador current, and Gulf stream; and, 

 with less submergence, the same in part, modi- 

 fied by the courses of the valley's .and the tides. 



It is to be noted, that the New-Haven region, 

 in Connecticut, is the southern extremity of the 

 Connecticut valley. The mean trend of this 

 valley in Connecticut is about S. 1 5"^ W. , and, in 

 southern Connecticut, S. IS" W. Now, the nu- 

 merous scratches o\er the eastern portion of 

 tlie New-Haven region average in direction 

 S. 1G° AV. ; but along its western border, where 

 the rapidly rising slopes give the region rather 

 an abrupt limit 150 to 350 feet high, the 

 scratches have an average course of S. 'M° W., 

 the extreme being S. "27° W., and S. 55° W. ; 

 and S. 3:5° W. is the almost uniform trend over 

 the undulating surface of the country for six 

 to niue miles west. It is, as far as 1 can see, 

 impossible that the valley stream should have 

 had on its west side so wide a divergence 

 from the direction of the Connecticut valley : 

 all the features of the region oppose it. Tlie 

 scratches are well exposed over the metamor- 

 phie rocks in man}- places ; and lai'ge and per- 

 fect examples of roches moutonnees here occur. 

 Again : over the higher lands of western 

 Connecticut (and of New England generally, 

 according to the obser\ations of Prof. Edward 

 Hitchcock. Prof. C. II. Hitchcock, and others), 

 the direction of the scratches is south-eastward. 

 To have produced them, if icebergs were the 

 agent, the submergence should have exceeded 

 •2,500 feet, and this would have given a chance 

 for the full play of the oceanic currents ; and 

 yet the above direction does not correspond 

 with that of either of the great currents. 



//. Distribution of the drift. 



Bowlders of trap, from 50 to 1 .000 tons in 

 weight, are numerous in the New-IIaven region, 

 especiallj' along its western border. All are 

 Connecticut - valley travellers ; for the trap 

 ridges of the valley — 400 to 1,300 feet in 

 height — are the onl}- possible source. They 

 were gathered up by the ice from these trap 

 ridges, and were carried 15 to (JO miles dowTi 

 the valley. It is mechanically impossible that 

 the larger bowlders should have been taken up, 

 or gathered in any waj', by floating ice ; either 

 shore-ice, where the water was but 1,000 feet 

 deep and less, or by that of icebergs, where 

 the depth was greater. 



It is well known, that the distance of drift 

 transportation is in general less tlvin 20 miles. 

 Hills of but JOO feet often have their long 

 trails. A moving glacier would easily gather 

 and carry along the nuitcrial fiom hills, high 

 or low, wherever loose or detachable masses 

 of rock or gravel existed to be gathered ; while 

 floating ice wouhl be \ery poor at gathering, 

 and hence inetlicient in distributing. 



