August in, 1883.] 



SCIENCE. 



1G7 



described a great natural dam across the valley of the 

 Great Valley Creek, near I'eth, where the moraine 

 stretches across the valley from side to side: and he 

 spoke of the contrast between the numerous drain- 

 age valleys which draiiieil the waters of the melting 

 ice into the Allegheny Hiver, and those valleys which 

 took their rise south of the moraine, and were free 

 from all drift. 



After giving some details of the western lobe of 

 the ice-sheet, and dwelling upon the agricultural 

 significance of the moraine, he spoke of some curious 

 deposits of glaciated material which occurred in a 

 narrow strip of ground immediately in front of the 

 moraine, and which he had named the ' fringe.' 

 These deposits ccmsisted of bowlders of Canadian 

 granite, and other rocks, which he found perched 

 upon the summits of hills, sometimes as far as five 

 miles in front of the moraine, though never farther. 

 This glacial ' fringe,' confined to the western part of 

 the state, was found to increase in width from two 

 miles in Warren county to five miles on the Ohio line. 

 and was at first a puzzling phenomenon. The hy- 

 pothesis suggested was, that, like l)reakers on the sea- 

 shore, the top of the ice overreached the lowest strata 

 by the width of the ' fringe,' and that while the 

 moraine marked the halting-place of the bottom of 

 the ice. by which it was formed, the far-transported 

 bowlders were carried on more rapidly in the top 

 strata of the ice, and were dropped outside of the 

 moraine to form the ' fringe.' It was stated that the 

 striae in the western part of the slate all pointed 

 south-east, being at right angles to those in the 

 eastern part of the state, but, like them, pointing 

 always towards the moraine. 



In conclusion, the author reviewed the more im- 

 portant facts discovered during his exploration of 

 the line of the moraine, dwelling upon the cliaracter 

 of the moraine where crossing river-valleys, the 

 absence of proof of any tongues of ice down .such 

 valleys, the absence of glacial drift south of the 

 moraine, the very slight erosion caused by the pas- 

 sage of the glacier, and especially upon the deflec- 

 tions, large and small, in the line of the moraine, 

 which were inexplicable on any other hypothesis 

 than that the moraine now described was pushed out 

 at the foot of a continuous ice-sheet of immense e.\tent. 



LETTERS TO THE EDITOR. 

 Change of birds' notes. 



For some year.* it has been known to many about 

 here, that in one locality the cardinal bird (Cardinalis 

 virginianus) has been in the habit of imitating the 

 notes of the whippoorwill (Antrostomus voclferus). 

 From articles I have read from time to time in vari- 

 ous scientific journals, I infer that it is not generally 

 known that birds ever, in the wild state (especially 

 cardinalis), change their song. I therefore thought 

 it well to report this case. I have in several instances 

 known this bird torliaiigeitssong, under confinement, 

 for one entirely different; but this is the only case I 

 have ever known where such a thing has occurred in 

 the wild state. I have known of this case for about 

 ten years. F. O. J. \ cons. 



Xewark, I.lcldng county, O. 



St. David's rocks and universal law. 



The article with the above heading in Scibnce of 

 .lune 15, by Dr. if. E. Wadsworth, has just come 

 under my observation; and. as it refers to questions 

 which have arisen chiefly in consequence of my re- 

 searches among those rocks, I shall deem it a favor 

 if you will allow me space in Science for a few 

 remarks in explanation. Professor Geikie's paper 

 was written with, as he states, 'a sense of duty' to 

 ' defend the views of his predecessors; ' and it is per- 

 fectly certain, from the hasty manner in which the 

 work was gone over by Professor (Jeikie aiul his two 

 assistants, that the object was to vindicate the work 

 of the Geological survey of thirty or forty years ago, 

 rather than to apply the knowledge gained by the 

 work of many independent observers since that time 

 to correct the errors well known to have been com- 

 mitted by the surveyors, which remain as blots on 

 the maps even now issued by the (ieologieal survey. 

 In the district of St. David's, these maps show a great 

 intrusive mass passing under the city of .St. David's, 

 about eight miles in length, ami with an average 

 wi<lth of about a mile. The southern jiorlion is 

 called syenite, and the other felslone. The rocks ly- 

 ing along the north-western edge for about a mile in 

 width are colored as altered Cambrian, presumably 

 as the result of the intrusion; but on the south-east 

 the rocks of the same age are supposed to be in con- 

 tact with the mass in an unaltered condition, and 

 without even a line of fault to separate them. These 

 appearances were curiously anomalous if true : hence 

 I felt it necessary to go very carefully into the ques- 

 tion. My large acquaintance with the district, and 

 the knowledge I had obtained in my explorations 

 among the lower fossiliferous rocks of the area, 

 enabled me to do this with some advantage. I had 

 also, from time to time, much valuable assistance 

 from Professors Ilarkness, Hughes, and Bonney, and 

 from Mr. T. Davies of the British museum, Mr. 

 Tawney, etc. 



I found that under the same name, rocks of very 

 different characters had been grouped together. The 

 so-called syenite ridge was seen to consist in part of 

 granitoid rocks, but also of quartz-felsites, of hiille- 

 flintas. of breccias, and of porcellanites freely trav- 

 ersed by intrusive dikes of various kinds. The so- 

 called metamorphic Cambrian on the north-west was 

 soon discovered to be an entirely distinct series from 

 any Cambrian rocks known in the district, or, indeed, 

 anywhere in Wales, and to be largely made up of 

 voii-anic rocks; and the basal Cambrian conglomer- 

 ate, as marked on the survey-maps, was shown to 

 overlie the granitoid, the quartz-felsite, hiilleflinta, 

 and the volcanic schistose and breccialeil scries un- 

 eonformably, and to be mainly made up of fragments 

 derived from those series. From the examination of 

 the conglomerates also, it w.is seen that there were 

 distinct evidences of their having been deposited 

 along old coast-lines, and that their materials varied 

 with the rocks upon which they repo-^ed; also that 

 these pre-Cambrian rocks must have been much in 

 the condition in which they are now found, before 

 the Cambrian conglomerates were de]>osiled upon 

 them. Curiously, also. I found that many of the 

 masses colored as intrusive greenstones 6n the sur- 

 vey-maps were highly acid rocks, and others in- 

 durated volcanic ashes' of pre-Cambrian age. Indeed, 

 nearly all the so-called intrusive masses marked so 

 abundantly on the survey-map among the older rocks 

 in the St. David's area have been prove«l beyond doubt 

 to be the result of erroneous observation; and yet 

 we are told by the present director-general that little 

 or no change is required in these maps, and that he 



