HISTORY OF GRITS AND SANDSTONES. 



21 



Analyses* . 





I. 



II. 



III. 



IV. 



V. 



Water 1 h yg rometric 



VVatei { combined 



•125 

 •935 

 80-600 

 9-200 



1- 025 

 076 



trace, 

 trace. 



2- 370 



•232 



-L 00\J 



1-285 

 1-647 

 1-372 



" -150 

 •700 

 75-750 

 8-227 



•050 

 1-290 

 87-400 

 3-997 

 1-876 

 trace. 

 •060 



•400 

 •850 

 85-550 

 7-570 



•150 

 •300 

 87-150 

 3-948 

 1-200 

 trace. 

 •094 



1- 352 



•203 



2 - 681 

 1-080 

 1-273 



•840 



Carbonic anhydride 





0-15 

 •171 

 10-521 

 1-352 



trace. 



•360 

 1-059 

 1-283 



•070 



trace. 



Ferrous oxide 



Ferric persulpbide (FeS 2 ) . 

 Manganous oxide 



1-366 

 •300 

 •279 



•684 

 •741 

 •332 



1-915 

 •753 



Soda 



•588 

 •612 

 ■915 

 1-113 





100-197 



100-120 



100-307 



100-336 



100-271 



Specific gravity 



2-689 



2-464 



2-710 



2-531 



2-660 



I. Grit, Cambrian : Barmouth, JSTorth Wales. 



II. Sandstone, Carboniferous f : Toredale Series, Shalk Beck, Cumberland. 



III. Sandstone, Carboniferous: Millstone- Grit Series, Brigham, Cumberland. 



IV. Sandstone, Carboniferous: Lower Coal-measures, Spinkwell quarry, 



Bradford. 



V. Sandstone, Triassic : Bunter, Bootle Well, Liverpool. 



Examination of Water- borne Sands. 



"With the view of to some extent studying the action of running 

 water upon the mineral fragments which it transports, a microsco- 

 pical examination was made of the sands of the St. Austell river, in 

 Cornwall. This stream, which during the summer months is a mere 

 rivulet of moderate size, sometimes in winter becomes a considerable 

 torrent. Its eastern arm arises at a distance of two miles and 

 three quarters from the town, and at a height of 470 feet above the 

 foot of the weir at the "Old Bridge." Its western arm, which meets, 

 the other a little north-west of the town, takes its rise in a small 

 valley only a mile from the point of origin of the more easterly 

 branch. From the bridge the distance to the sea at Pentewan is 

 four miles, while the total fall is only 114 feet. 



This stream formerly carried with it into the bay vast quantities 

 of the granitic sand which is separated by washing from china-clay 

 at the different clay-works in the district. As, however, catch-pits 

 have of late years been employed for the purpose of retaining it at 



* Since the above were completed, my attention has been directed to some 

 analyses published in U.S. G-eol. Survey, XLth Parallel, vol. ii. pp. 35 & 246, 

 which agree very closely with those here given. 



t A white fine-grained sandstone, much spotted with brown. 



