12 GEOLOGICAL RESEARCHES IN 



The porphyry conglomerates, No. 2, which, in places along the northern edge of 

 the basin, have a thickness of not less than 2000 feet, are wanting in the eastern 

 part. The parts of the series marked No. 3, form the oldest beds, and they 

 rest immediately on the limestone in their respective localities. Between Nos. 3 

 and 4 the character and extent of the intervening beds were not observed. The 

 connection between Nos. 4 and 5 is made on lithological grounds, the same green 

 sandstone and green quartzose conglomerate occurring above the coal seams of 

 Muntakau, and low down in the series at Chaitang. 



Limestone. — Here, as on the Yangtse, a great development of limestone ^rms 

 the floor of the Coal measures. Although no good opportunity occurred, in this 

 region, for estimating its thickness, this is undoubtedly several thousand feet. It 

 is generally divided into two nearly equal parts by a bed of clay slates ; though 

 independently of this, the upper and lower strata are characterized, the latter by 

 an abundance of chert, and the former by comparative freedom from that mineral. 



The limestone is generally compact and blue, but in places it is white and sac- 

 charoid ; and black, pink, and dark red varieties occur. The chert is black, and 

 is abundant in the lower half, occurring in nodules, and in layers varying in thick- 

 ness from less than one line to over forty feet, beds of this size generally forming 

 the bottom of the limestone. In the basin of Siuenhwa (fu), near the Great 

 WaU, the limestone is highly siliceous, but almost always retains a white appear- 

 ance. 



This formation furnishes, here, as in almost every province of the empire, besides 

 lime, the marble so much used in Chinese ornamental architecture, for bridges, 

 tombstones, gateways, and the lions that guard the portals of all official buildings. 

 The white saccharoid variety is very beautiful, but disintegrates so rapidly that, 

 even in the dry climate of Peking, inscriptions on exposed monuments two hundred 

 years old are barely legible.^ The black variety, which is very compact, breaking 

 with a conchoidal fracture, retains a perfectly fresh surface after centuries of 

 exposure. 



A quarry at the Maanshan has supplied lime for the capital during many centu- 

 ries ; the continued excavation having widened and deepened the valley, removing 

 Small hills and leaving, over an area of perhaps one square mile, a deposit that 

 might well perplex an observer, were the cause not still at work. Almost every 

 point in this area seems to have been the site of a lime-kiln, which has left its 

 cone of concentric layers, consisting of half burnt limestone, chert, fragments of 

 coal and ashes. As new kilns were built over and between old ones, the result is 

 a bed, the ingredients of 'which have become cemented to a hard concrete, by the 

 refuse lime. In this deposit, the stream of the valley has cut its channel, in places, 

 forty to fifty feet deep, with vertical walls, without reaching the limestone bottom. 



Caves are abundant in this limestone, and many of them are said to be of great 

 extent. One which I visited, near Fangshan (hien), consists of a series of large 



' There ,is a white variety, used in monuments near Peking, in which inscriptions of the Kin 

 dynasty are perfectly fresh, as, for instance, that used in the grand marble arch of Kiyungkwan in 

 the Nankau pass. 



