REPORT ON THE GEOLOGY OF ESSEX CO., MASS. 131 



It has been classed by authors as one of the felsite series, 

 but in thin sections, studied with the microscope, it is 

 seen to be composed of clastic grains of quartz and feld- 

 spar in a ferrugineous pasty cement. At Saugus Centre 

 it is interstratified with a conglomerate and is clearly one 

 of the lower members of the Olenellus Cambrian rocks. 



No. 28. Andalusite-Schist. 



This rock which is seen in Crescent cove, Nahant, at 

 Glenmere, Lynn, and also in Beverly, at the base of Goat 

 hill, is a metamorphosed slate with veins of andalusite de- 

 veloped in the bedding planes. 



VEIN ROCKS. 



No. 29. Lead, Silver and Copper Ores. 



This nuniber only occurs on the map to mark outcrops 

 where I have actually colleeted specimens of these ores. 



As the town boundary lines have been placed upon the 

 map, thus making the location of the various rock-masses 

 comparatively simple, and as the numbers are invariably 

 placed upon the outcrops of the rocks designated, further 

 explanations seem supernuous. 



In printing the map a few unimportant errors have 

 crept in and some smaller outcrops are omitted which 

 will be treated in other papers hereafter. The figure 18, 

 indicating limestone, slate and sandstone, placed at the 

 southeast of Glenmere, Lynn, should have been placed 

 between Glenmere and lake Wenuchus and covering the 

 territory to near Brown's pond in Peabody. Near lake 

 Wenuchus may be seen a fine contact of the slate and 

 hornblende-diorite, and west of Mr. Shorey's house, at 

 the f oot of Detroit street, there are good contacts showing 

 the hornblende-oranitite cutting the old Cambrian slates. 



In closing this report I desire to acknowledge my in- 



