1881.] 
275 
[Wadsworth. 
ing and important question. The adjacent rock is the Quincy 
Granite modified to a certain extent, as it is well known to be 
elsewhere when in contact with or near other rocks, that were in 
situ prior to* it. 
The writer found the argillite and granite in close relations a 
short distance east of the Paradoxides quarry, at a locality where 
both rocks were formerly quarried. This locality forms during 
high tide a peninsula or island, and the place can be readily found. 
On digging through the broken, fissured rock, the exact con- 
tact was found and specimens obtained which show both rocks 
and the line of contact (Nos. 1329-1338, 1346, 1347). 1 
The slate near the junction is greatly indurated and changed 
in color, while the granite is compact and has lost its distinctive 
characters, being transformed into a spherulitic quartz-porphyry. 
Small fragments of this modified form of the granite had been 
observed by Mr. Crosby, but he seems not to have understood its 
nature nor to have seen it in situ (Contributions 2 1880, p. 62). 
The modification of the granite, the induration and alteration 
of the argillite, the complete welding of the two formations, and 
the irregularity of the line of junction, prove that the granite is 
an eruptive rock, whose period of eruption is of later date than 
the Primordial argillite (No. 1339). 
This gives the contact on the eastern side of the argillite. If 
we pass to the western side we shall find that between the two 
rocks a depression exists, and the outcrops of the granite and 
argillite are some distance apart, while the junction is concealed 
under a deposit of drift. It hence was expedient to seek for the 
western contact elsewhere. 
This contact was found on the north side of Hayward’s Creek 
beyond which the argillite and granite are both prolonged. This 
contact was found by digging on the north side of the road, run- 
ning in an easterly direction, near the Creek. The depression 
marking the junction on the south side of the Creek was found 
to be on a line from the above point of contact S. 20° E. The 
1 These numbers refer to specimens in the Lithological collection at the Museum of 
Comparative Zoology, Cambridge, Mass. 
2 Occas. Pap. Bost. Soc. Nat. Hist.,m. 
