68 TRANSACTIONS OF THE [F£B. 1, 



appears. The following analysis shows how basic the rock is, and 

 that the silica is reinarkablv low for one with orthoclase : — 



In the last analysis (J. F. Williams, Igneous Rocks of Arkansas, 

 p. 220), there is" additional TiO, l.r.2,>eS, 0.89, P.^^ 0.35, and 

 traces of several other elements, making a total of 100. o1. The 

 specimen had evidently suffered alteration, but shows some close 

 analogies with the first analysis. It is an elaeolite mica S3*enite, 

 the Cove type of Williams. The locality of specimen 30 is near the 

 northeast corner of 5 B of map. 



Still further south, at the extreme end of the dike, syenite occurs 

 like that at the north. Along the highway it has crumbled away 

 to sand, as was noted by Haeusser, and only by searching can 

 fresh material be found. The slides show it to be like the syenite 

 of the northern end, and cancrinite again appears. The porphyritic 

 type is also to be had in float material. 



We may say of the dike in general that it is normal elaeolite- 

 syenite at its extremes, but that it becomes more basic toward the 

 southern portion. It may consist of several different outflows 

 along the same line. It uniformly contains aegirine and more 

 especially in the contact and southern parts has biotite. It is pene- 

 trated in places by subordinate dikes of elaeolite porphyry. The 

 analyses bring out forcibly the extraordinary range in composition 

 which elaeolite-.syenite may take, running down into the extreme 

 basic end of the series of rocks. The same thing is shown in Ar- 

 kansas, to an even greater degree, by J. F. Williams. This is only 

 rendered possible by the intermingling of orthoclase with such ba.sic 

 minerals as nepheline and sodalite and by relatively abundant bisili- 

 cates. The rock has been consistently called elaeolite-syenite through- 

 out the text, because it was studied in close association with J. F. 

 Williams, by whom the name was preferred for the Arkansas expo- 

 sures and is used in work already published. With the decadence 

 of the time element in petrographic classification, there is no good 

 reason (nor, indeed, ever was) for preserving the names elaeolite 

 and nepheline for the same mineral, and it would be far better to 

 use the latter term, which is recognized by the mineralogists. As 

 is done b}'' the French, the whole group might better be called 

 nepheline-syenite. 



It is unfortunate that the Beemerville exposure is situated in a 

 region where no streams of any size cross it — where no railroads or 

 artificial cuts in all probaliility will ever open it up — and that it is 

 quite densely covered with woods over almost its entire extent. 

 The conditions are unfavorable for good exposures. 



The AsHociafed Basic llorls. — As already remarked, it is a 

 curious fact that peculiar basic dikes are almost univer.^^ally asso- 



