July 20, 1900.] 



SCIENCE. 



93 



occur, until in the second row of hills 

 anorthosites replace them. The exposures 

 of limestone can only be traced a short 

 distance on the strike, say 200 yards before 

 they are concealed, but they have all the 

 appearance of a regularly stratified, sedi- 

 mentary rock, and their contacts give no 

 evidence of igneous metamorphism. They 

 dip into the mountain at about 40 degrees. 



Ihe Lewis Section of Quartzite. — About one 

 mile west of Lewis post-office a ledge of 

 graphitic quartzite arises out of the sandy 

 terrace and, with a dip of 25 degrees to the 

 west, extends for quite 100 yards without a 

 break. It then dips under a series of 

 graphitic gneisses, which may be found a 

 little to the south across a narrow gulch. 

 Still further westward and after an interval 

 that is concealed, the anorthosites appear 

 in a hillside. To the eastward of the 

 quartzite ledge everything is concealed by 

 a half mile of sand and then anorthosites 

 again appear. The quartzites and their 

 associated, graphitic gneisses present every 

 character of a sedimentary series and while 

 examining them one cannot resist the con- 

 viction that one is face to face with a frag- 

 ment of an ancient series of elastics. Fur- 

 ther south the anorthosites have been found 

 outcropping within- less than 50 feet of the 

 sedimentary rocks and with abundant evi- 

 dence of contact metamorphism. 



The Two Exposures in Limekiln Moun- 

 tain. — In the southwestern corner of Lewis 

 and near its line with Elizabethtown, there 

 arises a bunch of peaks, called Limekiln 

 Mountain on the maps of the TJ. S. Greolog- 

 ical Survey. The main summit is about 

 3000 feet above sea level. A number of 

 valleys and gulches separate the mountain 

 into several knobs. A gradual, drift-cov- 

 ered slope rises from the valley on the east 

 to a height of about 1400 feet above tide, 

 and then the shoulder of the mountain 

 ascends quite abruptly. Just in the foot of 

 this slope a ledge of limestone 20 to 30 feet 



thick has been opened up for quicklime. 

 The dip is very flat, being almost horizontal. 

 The exposures extend perhaps 50 yards and 

 then are concealed by soil. The rock be- 

 neath the limestone is not shown, but ex- 

 cellent opportunities are afforded to run 

 tlie section up the hill for a considerable 

 distance. For 50 feet across the dip 

 gneisses appear which are shown by the 

 microscope to contain quartz, microperthite, 

 some plagioclase, augite, and magnetite. 

 After a concealed interval, rocks of a gab- 

 broic character are met, consisting of labra- 

 dorite, green augite, garnet and magnetite, 

 but with no microperthite or quartz. If 

 now we pass across the high ridge to the 

 westward and down into the next valley 

 evidences of limestones not well displayed 

 may be discovered and then a quarter of a 

 mile further and somewhat southwest from 

 the first locality a beautifully exposed and 

 regularly bedded stratum, 20 feet in thick- 

 ness and dipping not more than ten degrees 

 into the mountain is revealed in old work- 

 ings for quicklime. Its general strike and 

 dip are closely parallel with the one just 

 mentioned, on the other side of the moun- 

 tain but it has this advantage, that the 

 gneisses are well shown beneath it, and one 

 can climb th« steep ledges of gneiss above 

 it for more than a thousand feet of cross- 

 section. They are the same quartzose, 

 microperthitic gneisses mentioned a mo- 

 ment ago. The limestone itself forms a 

 very flat and gentle roll and then disap- 

 pears under the talus in each direction. 

 Other small rolls can be traced out in the 

 direction of the dip, before they disappear 

 for good. In the bottoms of brooks in this 

 same portion of the mountain, graphitic 

 gneisses have been met, fairly remote from 

 the limestone, but the forest growth is so 

 thick and the exposures so fragmentary 

 that connected structural details cannot 

 well be worked out. 



These two separated ledges of limestone 



