48 History of Hingham. 



ing somewhat back from the beach are conglomerates. Proceed- 

 ing further a short distance, two dikes of diabase jut upon the 

 beach, and not far inland may be seen to have cut through con- 

 glomerate, the line of junction on a facing of one of them towards 

 the water being distinctly perceptible The lirst of the dikes is 

 about 450 feet from the porphyrite on the line of the beach, and 

 the second about 40 feet further. The former of these will be 

 more particularly mentioned before the close of these remarks 

 upon Rocky Neck. Beyond the dikes, extending over the beach 

 and along the shore for 350 feet or more, is a confused mixture of 

 melaphyr with other rocks, petrosilex, porphyrite, granite, quartz- 

 ite, etc. In portions the melaphyr forms with them a conglom- 

 erate of which it is by far the larger part. Other portions can 

 hardly be designated as conglomerate, being apparently the result 

 of the intrusion of the melaphyr in a molten state among pebbles 

 and masses unconsolidated, and absorbing them in its substance, 

 each being now found surrounded entirely by the melaphyr. 



It is in this portion of the rock of the shore that there is found 

 much good red jasper, affording cabinet specimens of some beauty. 

 The formation of this was clearly due to the chemical action 

 arising from the union of the molten melaphyr with the material 

 invaded. There are some veins of quartz found in the rock and 

 others of an impure, buff-colored epidote. 



Following this mixed melaphyr and conglomerate and less than 

 100 feet from it, is a very typical conglomerate containing peb- 

 bles of granite, quartzite, and petrosilex. This extends about 90 

 feet. The jointing in this may be noticed as north and south. 



About 80 feet from the conglomerate, melaphyr appears and 

 extends for the considerable distance of about 500 feet. In it 

 may be seen veins of quartz and also of the yellowish, opaque 

 epidote mentioned above as occurring in the mixed melaphyr 

 and conglomerate, but in far greater abundance. This melaphyr 

 at its termination abuts directly against conglomerate, the line 

 of demarcation being distinct and nearly vertical, though in places 

 this does not clearly appear. There is undoubtedly a fault here. 

 The conglomerate from the junction of the two rocks extends 

 along the coast line about 240 feet. In this conglomerate is an 

 east and west dike four to five feet wide. Melaphyr follows for 

 some 50 feet or more, of a character similar to that before de- 

 scribed as mixed with other material. 



A bay in the land here occurs, and crossing it westerly on the 

 beach at low tide the visitor finds cliffs of melaphyr which form a 

 jutting point into the water. Crossing this a second bay is 

 reached at a distance of about 100 feet. Here the rock displays 

 the characteristic nodules that lead to its designation as amyg- 

 daloid. Indeed a large portion of the melaphyr of Rocky Neck is 

 finely amygdaloidal, and affords good specimens of this variety of 

 the rock. On the beach here there is a protruding flat surface 

 of rock, a yard or so in diameter, on which may be seen glacial 



