M, J. Goldman — Catahoula Sandstone of Texas. 263 



of the sands was therefore possible. This was made according 

 to the method of Thonlet* with only slight modification. 



The method consists essentially of decanting off the muds 

 and passing the sands thus obtained through bolting-cloth sieves 

 of the following meshes and average sizes of openings. 



Approximate 

 Mesh Size of opening Name of product diameter 1 



Coarse > l mm 



30 0-89 mm 



Medium l-£ mra 



60 0-45 



Fine |-i mm 



100 0*26 



Very fine £-l/25 mm 



200 0-04 



Extra fine < l/25 mm 



1 The approximate diameters in fractions given are for comparison later. 



In the " very fine " portion the heavy minerals are then sepa- 

 rated from the quartz and feldspar in a heavy solution of den- 

 sity between 2*7 and. 2*8. 



In the present instance the method was modified by ignoring 

 the decanted portion, since it was very fine, mostly colloidal 

 in appearance, there was very little of it, and being largely the 

 product of decomposition by KOH it has no significance for 

 the problem under consideration. 



Quantitative results. — The results of the separation were : 



Weight in Percentage 



grams 



Total sand 9'340 



Products: 



Coarse (4 grains) (0-002 ± )f tr. 



Medium 0-975 10*4 



Fine 4-995 53'4 



Very fine 3-175 34*1 



Extra fine 0-185 2-0 



9-330 99-9 



The accompanying diagrams (figs. 1 to 12, p. 269) show 

 graphically the relation of these different portions.^ 



*Thoulet, J. : (1) Precis d'analyse des fonds sous-marins actuels et anciens. 

 Paris: Chapelot et Cie., 1907, 220 pp. (2) Instructions pratique pour 

 l'etnblissement d'une carte bathymetrique-lithologique sous-marine. Bull, 

 de l'lnst. Oceanogr. No. 169, Monaco, May 25, 1910, 29 pp. [A condensed 

 statement of the method elaborated in (1), with some modifications.] 



f The balance used does not weigh accurately quantities less than - 005K m . 



X These diagrams are made after the method of Mohr (E. C. Jul. Mohr, 

 "Die Mechanische Bodenanalyse," Bull, du Dept. de l'Agr. aux Indes Neer- 



Am. Jour. Sci.— Fourth Series, Vol. XXXIX, No. 231.— March, 1915. 



18 



