182 
POPULAR SCIENCE REVIEW. 
the conclusion, suggested by M. Dewalque, that the Cornstone group re- 
presents the Middle and Lower Devonian groups of Devonshire, lying 
between the Old Red Conglomerate and the Upper Silurian. The Belgian 
1 Psammites du Condroz/ a great group of sandstones lying between the 
Carboniferous Limestone and the ‘ Calcaire du Frasne,’ is to be regarded as 
the representative of the Pickwell Down Sandstone, and therefore of the 
true Old Red, notwithstanding the presence in it of marine fossils. 
The principal conclusions to be drawn from these arguments are as 
follows : There is only one Old Red Sandstone properly so called, repre- 
sented in Devonshire by the Pickwell Down Sandstone, and in Scotland and 
Ireland by the so-called Upper Old Red, in which case the Old Red Sand- 
stone is not the equivalent of the marine Devonian strata, but surmounts 
them. Secondly, at the close of the Upper Silurian period, all the western 
and northern portions of the British Isles were disturbed and elevated into 
land surfaces, while subsidence and deposition of marine strata were taking 
place over the south of England and Wales, and adjoining parts of western 
Europe, the Lower and Middle Devonian groups being then formed. 
At the commencement of the Upper Devonian stage there was a general 
subsidence ; lakes were formed over the Irish and Scottish areas, on the 
shelving shores of which the Old Red Conglomerate was accumulated; 
and at the commencement of the Carboniferous period a further sub- 
sidence took place, bringing in the waters of the ocean over all the 
submerged areas. 
MINERALOGY. 
Hedyphane containing baryta from Laangban . — Lindstrom describes ( Jahr - 
buck fur Miner alogie, 1879, 896) this specimen as white to pale yellow-white, 
and except as regards its showing the barium reaction and higher specific 
gravity of 5*82, according in every respect with hedyphane. The analyses 
given below show, under I., the composition as found, and, under II., the 
insoluble portion subtracted as well as the lime' carbonate and a quantity of 
oxygen equivalent to the chlorine. 
I. 
II. 
Arsenic acid . 
. 28T8 
29-01 
Phosphoric acid 
0-53 
0-55 
Carbonic acid 
1-07 
Lead 9-19 
Chlorine 
3-05 
3-14 
Lead oxide . 
. 49-44 
4101 
Baryta . 
8-03 
8-27 
Lime 
* . 8-99 
7-85 
Magnesia 
0-24 
0-25 
Iron oxide 
0-08 
0-08 
Soda 
015 
0-15 
Potash . 
0-09 
0-09 
Insoluble residue . 
0-42 
— 
100-27 
99-57 
Excluding the iron oxide, potash and soda we have the general formula, 
3 (3 RO, As 2 0 5 ) + Pb Cl 2 
