﻿200 G. P. Merrill — " Pliocene Sandstones" 



ing fragment, and there are also present a few particles of 

 earthy matter. 



A second variety (35890&) is coarser, has a marly appearance, 

 and effervesces slightly under dilute acid, showing the presence 

 of calcite. The microscope shows but few particles of pure 

 glass, but very many that resemble the pulverized amorphous 

 ground mass of modern lavas. There are also a few crystalline 

 particles too small for accurate determination, but which are 

 probably feldspar, and other greenish dichroic ones apparently 

 hornblendic. 



A third variety (85890c) from this same locality is of slightly 

 coarser texture than either of the last, of a light gray color and 

 distinctly laminated. It contains a very considerable propor- 

 tion of crystalline calcite which evidently serves as a cement. 

 Fragments of the stone after treatment with dilute hydrochloric 

 acid to remove the calcite are found to consist largely of color- 

 less pumice dust, a few cleavage fragments of feldspar, folia of 

 deep greenish brown mica, and a few earthy and ferruginous 

 particles. 



Still a fourth variety (35890c?) is yet coarser and much firmer 

 in texture, of a light buff color, and appears much like an 

 ordinary fine-grained siliceous sandstone. Under the micro- 

 scope the individual particles are found to be both quartzose 

 and feldspathic (judging only from appearances, no measure- 

 ments being possible), with comparatively few flakes of pumice 

 dust. All are much eroded, and have evidently been subjected 

 to attrition by moving waters more than any of the others from 

 this locality. 



Beaver Head Canon. — We have but a single specimen from 

 this locality and this (35891) like the last mentioned, except 

 slightly coarser and with minute flakes of black mica. Under 

 the microscope a few polarizing particles are seen but they are 

 too small for accurate determination. The glass particles are 

 small but stout, and lack the sharp angles noted in the other 

 varieties. They are considerably water-worn. 



DeviVs Pathway. — But two samples were received from this 

 locality. The first of these (35893a) is fine-grained, and light 

 ash color like the finer varieties from Little Sage Creek and 

 Marsh Creek "Valley. Like them too it is composed entirely 

 of pumice glass, but of a peculiar appearance such as I have 

 never before seen, nor do I remember to have seen it described. 

 Each fragment, however small, appears, under a power of 105 

 diameters, to bear upon its surface several or many minute disc- 

 like bodies, colorless and nearly circular in outline. Under a 

 power of 420 diameters these are seen not to be in all cases 

 perfectly circular in outline, but several often coalesce forming 

 continuous chains of irregular form, such as are nicely shown 



