250 Scientific Intelligence. 



aerial deposition when the conglomerates and the cross-bedded 

 sandstones were formed ; but toward the end the encroachment 

 of the sea is indicated by the deposition of the marls and fossil- 

 iferous limestones. Elsewhere throughout the whole Mesozoic- 

 Tertiary series fossils seem to be wholly absent, although the 

 deposits are well fitted to preserve the remains of plants and 

 animals if any had existed ; but here the calcareous strata, which 

 show other evidences of being marine, contain fossils in abun- 

 dance. Above he limestones the strata are at first red, as though 

 the shallowing of the sea allowed the very highly weathered soil 

 of an old land mass to be washed farther and farther out into 

 the area of deposition. The succeeding formations, the pink and 

 brown sandstone and the brown conglomerate, show a nearer and 

 nearer approach to present conditions. It appears as though, 

 after the retirement of the sea, the land was covered with great 

 playas, on which water first stood in thin sheets, forming ripple- 

 marks in the mud, and then retired or was evaporated, allowing the 

 surface to become sun-cracked. As time went on streams began 

 to flow across the playas, at first slow and broad and able to cut 

 only shallow channels, which were afterwards filled and covered, 

 assuming the form of very thin lenses of a material slightly dif- 

 ferent from that of the surrounding playa strata. Then, as the 

 strength of the streams increased, sand was deposited over the 

 whole area, and the channels, now deep and distinct, were filled 

 with gravel. Lastly, gravel was deposited almost everywhere." 

 Central Turkestan exhibits a recently warped and elevated 

 peneplain the dissection of which is assumed to have begun in 

 the closing Tertiary, though the uplift is placed mainly in 

 Pleistocene time. Summit glaciers were found among the moun- 

 tains between Marghilan and Issik Kul. From his observations 

 upon the ancient moraines of these glaciers the author concludes 

 that: "Wherever old moraines are well developed they indicate 

 that the glacial period is divisible into two or more subdivisions ; 

 and where the valleys are large and reach high enough still to 

 contain glaciers the number of these subdivisions is five, marked 

 by successive moraines, each of which is smaller and at a greater 

 altitude than its predecessor. Two theories present themselves 

 as worthy of consideration in explanation of these facts. Accord- 

 ing to one there was but a single glacial advance and retreat. 

 The retreat was not accomplished uniformly or rapidly, but by 

 successive steps, after each of which there was a long pause that 

 gave opportunity for the accumulation of a moraine ; thus five 

 moraines were formed by each glacier and those now in process 

 of deposition belong to the sixth step of the same long retreat. 

 According to the other theory, each moraine represents a distinct 

 glacial epoch, during which the glaciers first advanced and then 

 retreated. Under this theory the intervals of retreat were as 

 warm as or warmer than the present and the ice retreated far 

 into the mountains during each of them. 



