1884.) 693 {Frazer. 
In the succeeding township, Willistown, it is stated of the rocks: ‘** * * 
Southernmost of all, a broad band of syenitic granite and hornblendic 
gneiss, in which latter are dykes of dolerite (as near Lukens’), and 
another band of serpentine. How would these facts agree with the 
hypothesis hinted at above, that the lower Primal was represented by the 
pseudo-quartz porphyry and feldspar porphyry ; that this was overlain 
by the quartzite proper; this by schists, and this by limestone ; that there 
had been first a synclinal valley of all these, and finally a break in or on 
the side of the valley, by means of which’ the lower measures had been 
thrown up on the south and planed off evenly,’’ ete. 
Under West Goshen township ‘fragments of dolerite are frequent, but 
no dyke was apparent.’’ In the description of West Marlborough town- 
ship, ‘‘Syenite apparently belonged toadyke, of which the exact position 
‘was not determined,’’ is noticed south of Doe run, and ‘loose pieces of 
dolerite were deemed insufficient to warrant the placing of this formation 
on the colored map’’ (p. 807). In the description of Hast Nottingham, 
fragments of syenite are mentioned, &e., &e. (p. 843). 
In addition to the above references in the text of ©, to trap, there are marks 
in the following localities on township maps used in the field by the speaker, 
which indicate the presence of igneous rock fragments which were not 
placed upon the county map because not sufficiently indicative of the 
position of the parent dyke: Hast Goshen, N.E., N. and N.W. of Goshen- 
ville; West Goshen, near water works; Hast Bradford, near Copesville ; 
Hast Marlborough, near Unionville ; West Marlborough, 8.W. and N.W. 
of Upland, near and W. of Woodville, etc. ; Lower Oxford, near Lincoln 
University, etc.; Hasttown ; Willistown, near White House P.O., N. and 
N.W. of Sugartown ; Highland, near Gum Tree and near Fairview School 
House ; Kennett; New Gardon, near Toughkenamon, ete. 
It is not pretended that these citations cover all the places where trap 
was found, but they will serve to indicate that in the opinion of some field 
workers, there is a long step to be taken from the occurrence of a num- 
ber of trap fragments on the surface to the establishment of a dyke in 
place. 
Prof. Lewis concluded his description by saying, that such a dyke 
would form an important feature in the geology of the State. In this the 
speaker agreed with him, though whether or not the line of the trap be as 
continuous as he has represented it, the belt of disturbance had been 
established long ago. 
But this dyke, if established, would be singularly confirmatory of the 
long fault and southern upthrow, which constitute the kernel of the speak- 
er’s hypothesis of the structure of the rocks in Southeastern Pennsylvania : 
for, that there should be a fracture filled with injected rock, following 
just the course which the speaker has ever maintained the fault to occupy, 
for ‘‘ninety miles ;’’ and that the upthrow in one place (not in Chester 
county) was, ‘‘several thousand feet,’’ in extent, would be clearly cor: 
roboratory of the speaker’s view. 
