The Geology of Hlngham. 27 



unusual quantity of sulphide of iron in crystals, as may be seen 

 in specimens from this locality deposited in the general collection 

 of the Public Library. 



The diorite of the area of this rock under consideration does 

 not follow on East Street beyond Kilby, as its trend which is 

 northeast and southwest, leads to its development along the latter 

 street which has the same direction, and where it is found show- 

 ing itself on the road and adjoining lands at various points for 

 more than half a mile. At the junction of East and Kilby streets 

 it follows the curve from the former to the latter directly in the 

 roadway. Passing northeast on Kilby, it may be observed in lim- 

 ited exposures on the left of the road until the crossing of the rail- 

 road is reached, where there is a lateral extension of it 300 feet 

 west on the line of the rails, and 150 feet east. About 500 feet 

 from the crossing it again appears on the left side of the street, 

 followed at a short distance by granite. On the right side of the 

 road at 940 feet from the railroad may be seen a rock exposure 

 presenting a face towards the street of about thirty feet, the first 

 portion of which for twenty feet is diorite, the rest being granite. 

 Proceeding; 420 feet more along the road there will be seen ledires 

 on the left side back from the street which extend for a further 

 distance of about 270 feet. These are all diorite. After passing 

 these 130 feet, there may be observed on the right of the road, and 

 just beyond the fence which borders it, a face of rock about twenty 

 feet in width, the first portion of which, about one third, is granite, 

 and the rest diorite. The two rocks are separated by a diagonal 

 line having a declination of 45° N. E., thus showing the latter rock 

 as resting somewhat upon the former. Just beyond this exposure 

 granite follows for a distance of about 70 feet. There are no fur- 

 ther exposures of diorite on the road towards Rockland Street, the 

 few outcrops of rock observed there being all granite. 



Another area of diorite exists near the eastern border of the 

 town towards Cohasset, showing itself extensively on Weir, East, 

 Side Hill, and Hull streets. 



On Weir Street going from East Street, there is scarcely any 

 other rock observable for at least one third of a mile. Beyond 

 this, it alternates more or less with granite for about one eighth 

 of a mile, when it gives place entirely to the latter. On the east 

 side of the street, 2,310 feet from East Street, there is an exposure 

 of rock presenting a face to the carriage-way, showing a singular 

 mixture of both diorite and granite. 



This will be again and more particularly referred to in remarks 

 to follow upon " mixed rocks," — a name given by Professor Crosby 

 in treating of a like association observed by him at Marblehead 

 and Salem. 



As a general fact, it may be stated here that the diorite of Weir 

 Street is not so clearly typical as that of East and Kilby streets 

 before described. A preponderance of the feldspar and partial 

 decomposition, gives it in some cases a dirty white exterior. 



