Notices of Memoirs—Arnold-Bemrose—On Toadstone. 559 
XI.—On tue Dereysuire Toapstone. By H.H. Arnoip-Bemrosz, 
M.A., F.G.S. 
PF\OADSTONE is a local name for the igneous rocks interbedded 
with the Carboniferous limestones of Derbyshire. It occurs 
in a district of 25 by 20 miles. The upper and lower portions of 
a bed are sometimes amygdaloidal. The spheroidal structure is 
often well marked, the columnar more seldom and less perfectly. 
Toadstone varies very much in the amount of weathering it has 
undergone. It often decomposes to a sort of clay containing nodules 
of less altered rock, so that it has been supposed that toadstone in 
some localities “replaces” a bed of clay in others. For this reason, 
and also because of the loose way in which the word is used by 
miners, statements as to the number of beds of toadstone and of 
the presence or absence of ore in it must be accepted with reserve. 
Careiul mapping over the whole district will be necessary to ascertain 
the actual number of beds. ‘T'wo at least may be seen exposed in 
several places, and there may be three or even four beds. The 
Black Hillock shaft has been supposed to be one of the vents 
through which the toadstone came up to the surface, because the 
bottom of the rock was not reached. Farey, however, maintains 
that this bed was sunk through, and a careful examination of the 
mine heap and shaft shows that the dolerite is not coarse-grained, 
and that there is no trace of agglomerate or tuff. An occurrence of 
lead-ore in the toadstone of the Wakebridge mine was next de- 
scribed. The rock in which the ore occurred, when examined under 
the microscope, proved to be a decomposed olivine-dolerite. 'The 
ore was as good in the toadstone as in the limestone. That the 
toadstone is contemporaneous with the limestone is proved by its 
being interbedded with the latter, by the occurrence of stratified 
tuffs in various parts of the district, and by the non-alteration of 
the beds immediately above the igneous rock, though in one or two 
places a clay bed below it has been caused to assume a columnar 
structure. 
Very many specimens have been collected from all the outcrops 
of toadstone, which are some fifty in number, and many of them 
have been examined under the microscope. The lavas consist mainly 
of olivine-dolerite, the augite being both in ophitic plates and in 
irregularly shaped grains. The rock is much more fresh and less 
amygdaloidal than has been generally supposed. The tuffs are in 
some cases well preserved, and the outlines of the lapilli very clearly 
defined. 
XII.—Tue Dissrcrep Voicano or Cranpatt Basin, Wyomine. By 
Protessor JospPpH Paxson IppDINGS. 
HE writer, in exploring the north-eastern corner of the Yellow- 
stone National Park and the country east of it, came upon 
evidences of a great voleano which had been eroded in such a 
manner as to expose the geological structure of its basal portion. 
The work was carried on as a part of the survey of this region 
