296 Dall — Miocene and Pliocene of Martha? s Vineyard. 



formation of the mirror in an interval of ten minutes after the 

 introduction of portions of this test solution whether it is 

 wiser to add the entire solution or to estimate the arsenic in 

 the entire solution from that found in an aliquot portion. 



We append the results of the analysis of several samples of 

 commercial copper, all of which were electrolytic, and of which 

 the last two represented, presumably, the very purest electro- 

 lytically refined copper obtainable commercially. 





Copper taken, 



Arsenic found, 



Percentage 





gram. 



milligrams. 



of arsenic. 



Sample A 



0-3 



0-015 



0-005 



" B 



0-3 



0-030 



o-oio 



« C 



i' 1 ' 



0-018 



0-0018 



(I' 



0-015 



0-0015 



" D 



\ l ' 



0-005 



0-0005 



ll- 



0-005 



0-0005 



Art. XLII. — Notes on the Miocene and Pliocene of Gay 

 Head, Martha's Vineyard, Mass., and on the " Land phos- 

 phate" of the Ashley River district, South Carolina / by 

 Wm. H. Dall, Paleontologist to the U. S. Geological Sur- 



vey* 



In 1844 Sir Charles Lyell printedf some notes on Tertiary 

 fossils collected by him at Gay Head which led him to the 

 conclusion that they were of Miocene age. In 1863 Dr. 

 Stimpson described a fossil crab from these beds,:}: but without 

 expressing a decided opinion as to its geological age. In 1890 

 Mr. David White, U. S. G. S., in discussing the Cretaceous 

 plant-remains of the Gay Head section^ gave references to 

 most of the literature relating to the Gay Head section, which 

 is also discussed in Bull. TJ. S. Geol. Survey, No. 84, by Dall 

 and Harris in 1892. It will not, therefore, be necessary to 

 refer more fully to these well known publications here. 



Notwithstanding the lapse of half a century since Lyell's 

 announcement, the present writer is not aware that any attempt 

 has been made to identify the fauna of the Gay Head Miocene 

 and determine its horizon relatively to other Atlantic coast 

 beds ; or even to positively confirm from paleontologic evi- 

 dence Lyell's determination, though on other grounds it has 

 been very generally accepted. 



* Published by permission of the Director of the Surrey. 

 \ This Journal, first series, vol. xlvi, pp. 318-320. 

 \ Boston Journ. Nat. Hist , vii, pp. 583-9. 

 § This Journal, vol. xxxix, pp. 93-101. 



