658 . B. N. PEACH AT^D J. HORITE ON THE 



12°-42° N., the latter being the prevalent direction. Indeed at 

 Houton Head the ice-markings are nearly parallel with the coast- 

 line, so that the sandstone blocks could not possibly have come from 

 Hoy. Blocks of the same rock are strewn on the hill-slopes above 

 Gorsness, to the north-east of Maes Howe. It is a significant fact 

 that not a single block of the granite or gneiss which occurs in situ 

 to the north of Stromness and in the island of Graemsa is to be 

 found in the Boulder-clay between Irland Bay and Houton Head, 

 or anywhere to the east of the axis of crystalline rocks ; but as 

 soon as the western limit of these rocks is crossed, numerous blocks' 

 of granite and gneiss are strewn on the slopes and along the clifF- 

 tops between Brak Ness and Inganess. Had the ice-movement 

 been from the north-west, the phenomena would have been precisely 

 the opposite of those we have described. 



In the southern islands this deposit is not abundant; but in 

 South Konaldshay, on the shores of Water Sound, east of St. Mar- 

 garet's Hope, we observed patches of it containing blocks of sand- 

 stone, flags, and chalk, with comminuted shells. In this instance 

 the shells, when being dislodged, crumble readily to a white 

 powder. 



Our friend Mr. E. Etheridge, Jun., who kindly examined the 

 shell-fragments we obtained in the Boulder-clay sections in Orkney, 

 informs us that, on account of the fragmentary character of the 

 material, it is impossible to determine many of the specimens. He 

 has, however, named the following : — 



Cyprina islandica. I Mya truncata. 



Astarte (hinge). I Mytilus (fragment). 



Saxicava arctica. | 



Mr. H. B. Brady, F.B.S., has also kindly determined the follow- 

 ing species of Poraminifera from the same deposit : — 



Miliolina seminulum, Linne. I Truncatulina lobatula, Walker. 

 Lagena sulcata, W. ^ J. \ Polystomella striato-punctata, F. ^ M. 



y. MOEAINES. 



One conspicuous feature connected with the Glacial phenomena of 

 Orkney is the remarkable absence of any traces of local glaciers 

 except in Hoy and the Mainland. When we consider the abundance 

 of moraine heaps in all the more important islands of the Shetland 

 group, this difference seems all the more striking ; but when we 

 remember the marked contrast between the physical features of the 

 two groups of islands, the difficulty at once disappears. As we have 

 already indicated, the only mass of elevated ground which would 

 be capable of nourishing a series of local glaciers, after the great mer 

 de glace had melted back from the Orcadian coast-line, occurs in Hoy. 

 Hence we find that in the valleys which drain the group of conical 

 hills in the north of that island moraines occur in abundance and 

 also of great size. Professor Geikie has already described several 

 examples which also came under our notice *. In the valley to the 

 * ' Nature/ vol. xvi. p. 415. 



