858 



SCIENCE. 



[N. S. Vol. III. No. 76. 



paratns is more or less cumbersome and 

 fragile on account of the stop-cocks it con- 

 tains. 



It appears to me that the separating tube 

 proposed by Smeeth (Proceedings of the 

 Eoyal Dublin Society, May, 1888, p. 58) 

 has not been fully appreciated. The prin- 

 ciple involved seems to be an excellent one, 

 and by modifying the shape somewhat it 

 can be much improved. With this end in 

 view, several of the tubes were made by 

 Eimer & Amend, of New York, after the 

 design indicated in the accompanying fig- 

 ure. The apparatus consists of a cup- 

 shaped base, A, with a hollow standard, 



the tube B, to contain the heavy liquid in 

 which the separation takes place, the stop- 

 pers C and D to close respectively the upper 

 and lower ends of this tube. All of these 

 separate parts have ground fittings, so as 

 to be water-tight. The tube is so simple 

 that no special explanation of the method 

 of using it is needed. It will be seen that 

 when the two stoppers, C and D, are out, 



it affords an opportunity to stir both the 

 material which has sunk to the bottom of 

 the tube of the standard A, as well as that 

 which floats upon the top of the heavy 

 liquid in B, and by repeating the process . 

 several times it is possible to easily secure 

 a complete separation. 



It will be readily seen, also, that by in- 

 serting the stopper D, the tube B, with its 

 contents of heavy liquid and light material 

 floating on its top, can be removed. The 

 heavy material can then be washed out of 

 A, leaving this heavy material entirely sep- 

 arated in the standard A. 



This apparatus, besides the advantage 

 already enumerated, is especially stable and 

 portable, and all the material during the 

 separation is free from exposure to the air, 

 featui-es which give its great advantage in 

 laboratorjf work. J. S. Diller. 



TJ. S. Geological Survey. 



CURRENT NOTES ON PHYSIOGRAPHY. 

 VALLEYS OF THE OZAKK PLATEAU. 



The account of the Ozark mountains re- 

 cently published by Keyes (see Science, 

 Feb. 21, 1896) is followed by a valuable es- 

 say from O. F. Hershey on the valleys of 

 the same region (Amer. Geol., xvi, 1895, 

 338-357); the conclusions of the two ob- 

 servers agreeing in general as to processes 

 of land sculpture, but diflering somewhat as 

 to geological dates at which various stages 

 of the work of denudation were reached. 

 A lowland peneplain has been uplifted to 

 form the Ozark plateau ; it is deeply dis- 

 sected around the margin, so that the dis- 

 severed hills are not inappi'opriately called 

 ' mountains.' The ancient lowland is called 

 a Tertiary peneplain by Keyes, and a Jura- 

 Cretaceous peneplain hy IIershej\ The lat- 

 ter describes certain broad and shallow 

 vaUey-troughs, slightlj^ depressed beneath 

 the general upland, as the work of Tertiary 

 time in the gently uplifted Cretaceous pene- 

 plain. He concludes that the meandering 



