202 Notices of Memoirs—H. Miller’s Study of the Till. 
serpentine in the fashion figured by Tschermak’ and others. The 
felspar of this rock seems by its extinction-angles to be near 
anorthite. ‘The most numerous generation is in elongated crystals 
with fine lamellation. There are also later felspars in shapeless 
crystals with wide twin-lamelle and strongly-marked zonary band- 
ing in polarised light. The magnetite is later than the dominant 
felspar and earlier than the augite; it sometimes shows rod-like 
aggregations of octahedra. The pale-brown augite, in plates with 
an ophitic tendency, has here again a marked hour-glass structure, 
although the dividing lines have often an irregular disposition, and 
even run parallel to the outlines of projecting felspar crystals. It 
may be remarked that the hour-glass augites of the Welsh rocks 
rarely exhibit the regularity of structure figured by Werveke, etc.’ 
Several rocks from Holyhead stand on the border-land between 
the diabases and dolerites, as those families are here defined. The 
present specimen seems best referred to the latter category, the 
porphyrische structur (Rosenbusch) being well marked: the absence 
of ilmenite and hornblende is also to be noted in this connection. 
Other dykes in Holyhead Island are marked on the Survey Map 
and mentioned by Sir A. Ramsay. They all strike in a general 
N.W.—S.E. direction, ‘“‘ which is also that of the fault which crosses 
Holyhead Mountain between Gogarth and Porth-y-corwgl, and all 
coincide more or less with the run of many of the larger joints.” 
We have seen that the dykes of the Menai Straits and the Coal-field 
have about the same bearing, but they show lithologically little 
resemblance with those last described ; and as the rocks cut by the 
Holyhead dykes are themselves of dubious age, speculation on the 
date of the dykes must necessarily be reserved. 
NOTICES OF MEMOTRS. 
Seas a TT 
IT.—A Comparative Stupy or THE TiLtL on Lower BouLDER-CLAY 
IN SEVERAL OF THE GLACIATED CountTRIES OF EHuropE—Britatn, 
SCANDINAVIA, GERMANY, SWITZERLAND, AND THE PyrENEES. By 
Hueu Miter, F.R.S.E., F.G.S., Assoc. R.S.M.° 
HE sections of foreign Till examined by the author occur chiefly 
in the neighbourhood of the Trondhjem Fjord in Norway, at 
Berlin and Leipzig in Germany, near the Lake of Geneva in Switzer- 
land, and in the valleys of the Pyrenees directly south from Pau. in 
Southern France. In these countries and in Britain the Till bears 
an identical character. It is not more variable throughout Europe 
than the author has found it to be in Scotland and Northern England. 
On the basement-gneiss at Christiansund in South-western Norway 
it is the same as on the basement-gneiss of Sutherlandshire; in the 
great limestone valley of Haux Chauds in the Pyrenees it is scarcely 
1 Sitzungsb. d. k. Akad. d. Wien. vol. lvi. p. 283, and plate, 1867. 
2 Neues Jahrbuch, 1879, p. 823. Hussak, Anleitwng zum bestimmen der 
gesteinbildenden Mineralien, p. 72; 1885. 
3 Read at the British Association, Manchester, 1887. 
