220 The American Geoloyinl. October, 18» 
From north to south the gradient is ahiiost horizontal between Orient 
and Armour, S. Dak., about 1,875 foet; V)ut in the James river valley, 
although it is nearly constant from Ellendaie to Huron, about 1,700 
feet, it drops farther south to 1,.330 feet at Mitchell, and rises again to 
over 1,500 feet at Tripp. 
The explanation considered most satisfactory is that given by Upham 
in the American Geologist for October, 1890 (vol. vi, pp. 211-221), re- 
ferring the eastward and southward decline in pressure to leakage 
from the Dakota sandstone along its eastern edge in Nebraska, Iowa, 
and Minnesota. It was suggested that actual irregularities of the pres- 
sure gradient may result from a complex arrangement of the water- 
bearing stratum, from inequalities in the leakage on the southeast and 
east, and from variations in the fineness or porosity of this sandstone. 
In conclusion, more careful measurements of the closed pressure of the 
artesian wells of the Northwest were recommended. 
.V. The true Tuff-beds of the Trias,(iH(l the mud enclosures, the under- 
rolling, and the basic pitchstone of t/ie Triassic Traps. B. K. Emer- 
son. This paper gave many interesting notes of field observations of 
the Triassic belt in the lower part of the Connecticut river valley. It 
was discussed by Dr. M. E. Wadswokth, who found striking resem- 
blances to what he had observed in the copper-bearing region of lake 
Superior. Prof. Rice reports it as follows: "In some localities the bro- 
ken surface of the extrusive trap sheets, with the calcareous or arena- 
ceous deposits mingled with the trap, has been rolled under in the on- 
ward flow of the trap, so that the same phenomena appear both at the 
top and bottom of the trap sheet. In certain localities the wet mud of 
the estuary bottom, over which the trap sheet flowed, has risen up into 
the trap, presenting an appearance very similar to that of true tuff beds. 
In these cases portions of the mud have been metamorphosed into a 
quartzite, and portions of the molten naaterial of the trap, chilled by 
the ascending currents of mud and water, have solidified into a pitch- 
stone or tachylite." The sections and quarries most notably showing 
these conditions are in Green fleld and Holyoke. Mass., and in Meriden, 
Conn. 
4. Volcanic Asii from the North Shore of Lake Sujjerior. N. H. 
WiNCHELL and U. S. Grant. Published in the preceding pages. 
5. The ''■Augen Gneiss," Pegmatite Veins, and Diorite Dikes at Brad- 
ford, Westchester county, N. Y. Lea McI. Luquer and Heinrich 
RiEs. To be published in the American Geologist. 
a. The Ti/ringhdin {Mass.) '^Mortise Rock," and pseudoniorphs of 
Quartz after Albite. B. K. Emerson. Specimens were exhibited, in 
which the quartz has minute cavities due to crystals of salite dissolved 
out. Psendomorphic quartz fills delicate casts of albite and cleaveland- 
ite, showing stria? and luster. 
7. The Succession of the Fossil Faunas in tlie Hamilton group at 
Eighteen Mile creek, N. V. Amadeus W. Grabau. The sections ex- 
hibiting the Hamilton beds, underlying the Genesee and Portage series, 
at Eighteen Mile creek (tributary to lake Erie about eighteen miles 
southwest of Buffalo) are situated between the L. S. it M. S. railway 
