Notices of Memows—Prof. Wallace—Brines of Manitoba. 31 
granophyres appear to be closely related to the extrusive rhyolites 
among which they are intruded. This fixes an upper limit to the 
age of the diabases in this district. 
The various beds strike more or less east to west, and dip steadily 
southwards at about 40° until the Talyllyn Mudstones are reached, 
when folding and rolling of the beds immediately begin. Two 
N.E.-S.W. shatter faults—the Dolgelley and Talyllyn faults—cause 
a certain amount of repetition, and give rise to the Dolgelley-Llyn 
Gwernon and to the Talyllyn Valleys, the former to the north and 
the latter to the south of the escarpment. A strike-fault between 
Mynydd Gader and Cader Idris cuts out the whole of the Bifidus Beds, 
bringing the Lower Acid and the Lower Basic Volcanic Series 
against one another. The intrusive rocks frequently cause local 
variations in the dip and strike. 
All the softer strata are strongly cleaved, so that fossils are difficult 
to obtain. The slates within the Lower Acid Series have yielded 
a few extensiform graptolites, while from the Bifidus Beds the 
characteristic fossils were obtained at numerous localities. The 
D. murchisont zone has not been recognized by the authors, its place 
presumably being occupied by a part of the Lower Basic Series. The 
dark mudstones among which the pisolitic iron-ore is developed have 
yielded rather obscure graptolites, which, however, indicate a fairly 
high horizon in the Llandeilo Series. The presence of Amplexograptus 
arctus and Glyptograptus teretiusculus var. euglyphus in the lowest 
beds of the Talyllyn Mudstones indicates a high horizon in the 
Glenkiln, or, in other words, a low horizon in the Caradocian, and 
suggests that the immediately underlying Upper Acid Series is at 
approximately the same horizon as the Snowdonian volcanic rocks of 
- Conway. This youngest of the four volcanic series on Cader Idris 
is therefore considerably higher in the Ordovician than has been 
previously supposed. The position of the boundary between Cara- 
-docian and Llandeilian has not yet been established, owing to the 
unfossiliferous character of the blue-grey mudstones of Llyn-y-Gader 
and Llyn-Cau. 
One of the authors (A. H. Cox) is indebted to the Government 
Grant Committee of the Royal Society for a grant which has partially 
defrayed the expenses involved in the investigation. The area is 
being mapped on the 6 inch scale. 
II].—Tne Corrostve Acrion oF CERTAIN Brines In Maniroza.’ By 
Professor R. C. Wattacr, M.A., Ph.D., B.Sc. 
RINE springs issue from Middle and Upper Devonian limestones. 
and dolomites at the foot of the Manitoba escarpment. At least 
eighty brine areas are known, with a total flow—during the dry 
season—of approximately 500 gallons per minute. The water 
circulates in the Dakota Sandstone, the basal member of the 
Cretaceous series, and extends laterally into the Devonian calciferous 
formation, from which it leaches sodium chloride, disseminated 
through certain dolomite horizons. The composition of the brines, 
1 Read before the British Association, Section C, Manchester, 1915. 
