SCIENCE- G OSSIP. 



and valleys around Barmouth, and much farther 

 afield, afford conspicuous evidences character- 

 istic of ice moulding by glaciers of great size. 

 The slates, flags, quartzose, sandstones, and con- 

 glomerates, all alike are crossed and recrossed by 

 polished and striated grooves, and many of the 

 hill-tops have been moulded into well-formed 

 roehes moutonnees. A series of upwards of twenty 

 of these bosses and domes lie on the summit of 

 Abermaw and Celfawr, immediately overlooking 

 Barmouth town, at a height of about 800 feet O.D. 

 Many other similar and equally well developed 

 examples occur on the sides and summits of most 

 of the neighbouring hills. From the top of 

 Abermaw may be seen, dotted here and there on 

 slope and crest, large perched blocks that have 

 been lowered gently into their present positions as 

 the glaciers that once carried them melted away. 

 One of these blocks, lying above Ceilwart, measures 

 18 feet 8 inches by 7 feet 6 inches. It demonstrates 

 admirably, in the polished and striated surfaces of 

 its under sides, the manner in which it had been 

 used in the grip of the glacier as a gouge to form 

 the grooves and striae on the hillside around it. 

 None of these perched blocks are " travellers," in 

 the glacial acceptation of the term. All are of local 

 origin, and may be traced to the Cambrian strata 

 in an area of a few miles. I was told of a 

 " granite " boulder having been seen on one of the 

 hills in the vicinity of Barmouth, but I was not 

 successful in finding it. I am inclined to think 

 that it was perhaps one of the many blocks of 

 felspar porphyry, which abound in the neighbour- 

 hood, that had their origin either in the Arrans or 

 Cader. In the course of my rambles around 

 Barmouth I saw no granites either on the hills or 

 in the moraines ; but I met with many felspathic 

 porphyritic rocks which, at first sight, one might 

 be excused for mistaking for granite. 



The lateral moraines of the glaciers that de- 

 scended the Mawddach from the Arrans and Cader 

 are a conspicuous feature around Barmouth. These 

 glaciers, after forcing their way through the Mawd- 

 dach estuary, spread out fan-shaped, and extended 

 right and left along what is now the shore line of 

 Cardigan Bay. Most of the walls and farm build- 

 ings between Barmouth and Harlech have been 

 built of the rounded and striated boulders ob- 

 tained from the morainal accumulations that 

 flank the hillsides and shore line between the two 

 places. Sections of the right moraine are well 

 shown at Llanaber with the debris and boulders 

 (Fig. 1). This portion of the moraine extends 

 from Llanaber to the Barmouth Morfa, where it 

 disappears beneath a stretch of sand dunes ; but its 

 continuation may be traced in the boulder -beach 

 which extends along the Barmouth sea-front. It 

 varies in thickness from 40 feet at Llanaber to a 

 thin stratum of stiff yellow clay at the Morfa. An 

 examination of the boulders shows that the accumu- 

 lations near Barmouth offer a greater variety of 



rocks than those near Llanaber. In all parts of the 

 deposit the Cambrian grits and shales predominate ; 

 but the beds off the Morfa also contain considerable 

 numbers of boulders of pyritous shale from the 

 Ordovician, felspar porphyries such as are to be 

 found at Arran Mowddy, dolerites from the Cam- 

 brian dikes, calcareous ash, and rubbly vesicular 

 conglomerates similar to those found at Cader. 

 These interesting beds would repay a careful and 

 patient investigation ; and to such as care to under- 

 take it I would suggest as the most favourable 

 points of attack the Llanaber and Morfa sections, 

 and also the left moraine which lies on the southern 

 side of the Mawddach. 



In the middle of the Mawddach estuary are 

 numerous islets, all of which show in their polished, 

 rounded, and striated surfaces that they are typical 

 examples of roehes moutonne.es formed by the old 

 Arran mer de glace. 



{To be continued.') 



BRITISH COCKCHAFERS. 



By E. J. Burgess Sopp, F.E.S. 



{Concluded from Vol. VI. page 355.) 



AS perfect insects cockchafers, which belong to 

 the Phyllophaga, or "leaf-cutters," are wholly 

 phytophagous and almost wholly crepuscular or 

 nocturnal in their habits. They shun the sunlight 

 during the day, when they may often be found cling- 

 ing to the under side of twigs and leaves, which, as a 

 rule, they do not quit until the approach of twilight, 

 when they commence to buzz about amongst the 

 branches of trees and shrubs to feed upon the 

 foliage. Their flight is clumsy and heavy, which 

 causes them to fall an easy prey to bats, owls, 

 night-jars, and other nocturnal creatures. Never- 

 theless, there are usually enough left to gladden 

 the heart of the coleopterist and more than 

 sufficient to satisfy the horticulturist whose apple- 

 trees, roses, strawberries, asparagus, and other 

 garden produce is often badly injured by these 

 destructive chafers, in either the larva or imago 

 form. Orchard trees that have been seriously 

 attacked are said not to bear satisfactorily for 

 several seasons afterwards. Julius Pollux, who wrote 

 towards the close of the second century, seems to have 

 noted some connection between the two, as shown 

 by the following passage : " The Melolonthe is a 

 winged animal which they also call Melolanthe, 

 either from the bloom of apples, or its occurring 

 with their bloom" (Bk. 9, ch. 7). 



As in the case of many other insects, the great 

 strength of the cockchafer becomes apparent to 

 anyone who takes the trouble to test it. In an 

 interesting series of experiments carried out by 

 Plateau he found that the ratio of weight lifted 

 to weight of body ('940 grammes) in one of these 

 insects was 14-3; but, as we all know, muscular 

 strength is not everything in this world, and when 



