1006 



SCIENCE 



[N. S. Vol. XXXIII. N®. 861 



classification are numbered to agree witli 

 Sherzer's types. The technical terms for the 

 mechanical types of the second column make 

 for uniformity as well as euphony, while lend- 

 ing themselves readily to compounding. 



A. C1.ASTIC SANDS 



(Exogenetic) 

 Sherzer's Types of Sands 



1. Glacial, etc., sand. 



2. Volcanic sand. 



3. Eesidual sand. 



4. Aqueous sand. 



5. iEolian sand. 



6. (Artificial sand) added. 

 Corresponding Divisions in Graiau's Classification 



1. Autoclastic sand or autoarenyte. 



2. Pyroelastic sand or pyrarenyte. 



3. Atmoclastic sand or atmoarenyte. 



4. Hydroclastic sand or hydrarenyte. 



5. Anemoclastie sand or anemoarenyte. 



6. Bioclastie sand or iioarenyte. 



B. NON-CLASTIC SANDS 



(Endogenetie) 

 Sherzer's Types of Sands 



7. Organic sand. 



8. Concentration sand. 



9. (Snow and firn sand) added. 

 10. (Lapilli or igneous sand) added. 



Corresponding Divisions in Grabau's Classification 



7. Biogenic sand.^ 



8. Hydrogenic sand.' 



9. Atmogenic sand.^ 

 10. Pyrogenie sand.' 



In my classification of sedimentary rocks, 



1 pointed out that after the determination of 

 the agent, the further subdivision of clastic 

 rocks must be on the basis of texture, and 

 that three textures are to be recognized as of 

 primary importance, namely, (1) rudaceous 

 texture, the texture of rubble or material 

 coarser than sand (i. e., approximately above 



2 to 2.5 mm.), (2) arenaceous texture or the 

 texture of sand (2.5 to .05 mm.) and (3) lu- 

 taceous texture or the texture of mud, i. e., 

 rock flour, clay, etc. These three types of 

 texture produce rocks, consolidated or uncon- 

 solidated, which may be classified as rudytes, 



' These are not arenytes in the sense used above 

 — i. e., for elastics only. 



arenytes and lutytes, respectively. Eudytes 

 and lutytes are found in each of the divisions 

 in which arenytes are found; we have auto- 

 rudytes and autolutytes, hydrorudytes, hydro- 

 lutytes and all the rest, just as we have the 

 various arenytes given above. Sherzer too is 

 fully of the opinion that the coarser- and 

 finer-than sand particles should be classified 

 on the same basis as the sand itself. 



Non-clastic, granular material constitutes 

 sands, etc., only in the broader or popular 

 sense of the term; while it is quite proper 

 to speak of organic or chemical sands, it is 

 desirable that the technical terms arenyte, 

 lutyte, etc., be restricted to clastic rocks only. 



Professor Sherzer further subdivides his 

 types on the basis of reworking by some 

 other agent. Thus he has an aqueo-residual 

 type in which grains originally of residual 

 (atmoclastic) origin are reworked by water. 

 On the other hand, a residuo-aqueous type is 

 one in which original aqueous sands (hydro- 

 clastic) have become weathered under the in- 

 fluence of the atmosphere. These two sub- 

 types may be termed, respectively, the 

 hydro-atmoclastic and the atmohydroclastic 

 subtypes of sands. In like manner the other 

 combinations may occur and we may have 

 anemohydro-, atmo- and autoclastic sands, 

 hydro-anemo-, atmo-, pyro- and autoclastic 

 sands, anemo-atmo-, hydro-, pyro- and auto- 

 clastic sands, terms which have at least the 

 advantage of euphony over the English 

 equivalents, such as seolo-aqueous or residuo- 

 ssolian. But the selection of terms is a minor 

 matter, the important thing being the correct 

 classification on a genetic basis, and this 

 Professor Sherzer has done for sands. I am 

 happy to find myself so fully in accord v^ith 

 him, and that in the endeavor to classify 

 materials he has come to substantially the 

 same results that I have reached in approach- 

 ing the matter from the more theoretical 

 basis of principles of classification. 



It may perhaps be questioned if the sec- 

 ondarily enlarged aeolian sand grains which 

 Professor Sherzer claims as concentro-seolian 

 should be included in this classification, which 

 is essentially one of the material in its orig- 



