July 23, 1920] 



SCIENCE 



' ' Galenif erous Limestone, ' ' whidi in turn waa an 

 alteration of Schoolcraft's usage of "Metallifer- 

 ous Limestone." 

 Rectification of Iowa's Cambric section: Charles 



Ketes. 



Recent critical inspection of the type localities 

 of the Cam'bric formations of the upper Mississippi 

 basin indicates that there are grave misinterpreta- 

 tions of stratigraphic succession. Thus, some 

 ■well-known formational titles ^become synonyms and 

 pass out of use; several names are new; and a 

 number of substitutions appear. Exact parallelism 

 of the upper Mississippi Basin section and that of 

 the Ozarks is thus satisfactorily permitted. 



The use of the terms flint and chert : W. S. Glock. 

 Common usage of these terms may leave such an 

 uncertainty that a, word dare not be employed 

 where scientific accuracy is desired. For example, 

 it is a common habit to call any form of quartz 

 interbedded with iron ore ' ' chert ' ' for want of 

 knowledge of the nature of the quartz and of the 

 meaning of the term employed. Detailed refer- 

 ence to the standard English and American text- 

 books on geology and mineralogy substantiated the 

 confusion which exists and which is presented 

 therein for the instruction of the reader. Neither 

 chert nor flint should be a provoking "catch-all"; 

 fundamentally they are good terms whose use is 

 justified only where exactness is implied. 



The fauna of the Independence Shale: A. 0. 



Thomas. 



This interestinig fauna, first reported by Dr. 

 Calvin over forty years ago from a very limited 

 exposure, has recently become better known due 

 to the discovery of several fossdliferous outcrops 

 of the shale as reported before the academy a year 

 ago. Among the additions to the fauna is a spe- 

 cies of the crinoid Arthracantha, hitherto known 

 only from the Devonian of the region of Lake On- 

 tario. There is also a species of Spirifer akin to 

 B. disjunctus, a new Chonetes, and a fine specimen 

 of Sypothyridina cuioides. A few of the species 

 of the Independence shale recur in the Lime Creek 

 shale at the top of the Iowa Devonian but none of 

 the forms just mentioned are known to occur in 

 the later formation. 

 Nortonechinus, a Devonian sea urchin: A. 0. 



Thomas. 



This is a highly specialized genus known only 

 from dissociated plates, spines, and parts of the 

 lantern. The test of the living animal was doubt- 

 less very flexible and was well protected by the 



covering afforded by the broadly expanded distal 

 ends of the spines as in modern Colobocentrotv^s. 

 Two other genera of echinoids also found in the 

 Lime Creek shales will be briefly discussed. 



The corals of the SopTcinton stage, Iowa Silurian: 



A. 0. Thomas and Beryl Taylor. 



The Iowa Silurian affords a rich and interesting 

 assemblage of corals miost of which are highly 

 Bilicified. The Calvin Collections from the typical 

 localities together with those made by various field 

 classes and by the writers, furnish a large series 

 in which some of the genera are very well repre- 

 sented. Strombodes, for example, has no less than 

 ten species, Favosites, seven, Zaphrentis, six, and 

 Seliolites, four. The reefs furnish upwards of 

 seventy species, many of which are new. 



The conservation of underground water: James H. 



Lees. 



The paper discusses the importance of water, its 

 source and distribution, its relation to the rock 

 strata and its use by plants. The need for better 

 conservation is emphasized and the effect of popu- 

 lation increase and of agriculture is discussed. 

 Certain post-Pliocene deposits in Missouri: B. 



Shimek. 

 On the occurrence of c'ha/rcoal in am, interglaoM 



peat bed in Union county : Balph W. Chaney. 

 A sinTc hole in nortlieast lotva: E. J. Cable. 

 A note on the progress of investigation of the 



lowan-Wisconsin border: E. J. Cable. 

 A field of esTcers in Iowa: John E. Smith. 

 The content of agricultural geology: John E. 



Smith. 

 The Palisades of the Cedar: Wm. H. Norton. 

 A comparison of the NebrasTcan drift with the 



Kansan drift: George P. Kay. 



Physics 



The Hall effect and tlie specific resistance of thin 

 silver films: G. E. Wait. 



The dependence of the resistance of silver films 

 upon the method of deposition : G. E. Wait. 



On the dynamics of an airplane loop: L. P. SlEQ. 



A new high frequency tone generator: C. W. Hew- 

 lett. 



The perception of binaural phase difference not 

 caused by an intensity effect : G. W. Stewart. 



The frequency limits of the binaural phase differ- 

 ence and intensity effects: G. W. Stewart. 



Note on the principle of similitude : I. Maizlish. 



