Von Ritchthofen— Geological Explorations in China. 411 
reddish or yellow color when converted into quartzite. They ha 
often a thickness of thousands of feet, and, as they are less aifeoted 
by denudation than many other st tratified rocks, they frequently 
compose mountain ranges for themselves, without offering any 
clue for determining their stratigraphical position. This is also 
analogy with the history of the exploration of the European Alps 
is striking. One cannot be astonished that the first explorer of 
Chinese geology, though a most admirable observer, should have 
distinguished only one great limestone formation in China, and 
tions. Since then ave come to the conclusion that it will not 
be difficult, on detailed examination, to establish in other regions 
a greater narabe r at distinct levels. 
Tt is for the various reasons peo oes that I examined eve 
a f fferent formati and 
tried to establish the analogy between different regions only after 
having completed the exploration of ea h - 
deal of additional support and, I think, si prove to bea near 
a to the true order of suece 
two previous letters (March 1st a Mos Sth) * a 
my having found Carboniferous fossils on the 
Shantung, in certain limestones and shales which occur per: in 
close connection with the e Coal-measures, or indeed form part of 
rial for determining the age of a formation which corresponds, 
stratigraphically and lithologically, with the lowest (“ Matsu”) 
limestone on the Yang-tse and the formation mentioned as’ No. 2 
thousand feet, and is, lithclogically, ex ly varied. It e 
sists of endless alternations of r canes argyllite and brown 
Sandstone, with strata of limestone, the — two prevailin 
= lower ans the latter in the upper e limestone it- 
ts a large number of poring and one can di 
os purely lithological grounds, several ho e order of suc- 
cession of which is similar in wide regions. De of these horizons 
other conspicuous varieties of limestone, extends from the Yang-tse 
to He egicioa and to Peking (twelve degrees of latitude and ten 
of. longit ude), 
