Dall.] 138 [October 20, 



October 20, 1869. 

 The President in the chair. Twenty-eight persons present. 



Dr. B. Joy Jeffries was appointed Secretary pro tempore. 



Mr. W. H. Dall described the alluvial deposits of the 

 Yukon River, in Alaska. Each annual layer is deposited in 

 three strata — gravel, mud and vegetable matter, according to 

 the specific gravity of the materials. In a bank near Xulato, 

 in a space eight feet high, one hundred and eighty annual 

 layers were counted. The vegetable matter in the lower 

 layers showed signs of carbonization. Some intervals 

 were noticeable where vegetation had attained a considerable 

 growth before it was overwhelmed by another inundation. 

 The roots and stumps were occasionally left in situ, the tops 

 having been broken off and carried away. 



A close parallelism was shown to exist between these Post 

 Pliocene deposits and the adjacent Miocene Tertiary strata. 

 In the latter the sandstones, though hard and often meta- 

 morphosed, were shown to consist of similar layers of sand, 

 mud and vegetable material. Perhaps a more complete ex- 

 emplification could not be shown of the theory that geological 

 action is going on at the present time at about the same rate 

 as in former ages. The manner and amount of deposition 

 in the present and in the Tertiary epochs, were thus proved to 

 be nearly identical. 



Four entirely unspotted eggs of the Corvus americanus, 

 obtained by Mr. S. Jillson in Hudson, were exhibited. Mr. 

 Jillson states that the previous year he found in the same 

 locality a nest of unspotted crow's eggs, probably the eggs 

 of the same pair. 



Dr. T. M. Brewer remarked that such a peculiarity in the 

 crow's eggs had never, so far as he was aware, been observed 

 before. A few birds, e. g. y certain kinds of flycatchers, vireos 



