202 



SCIENCE-GOSSIP. 



density of the rock could not be expected. There 

 is no idiomorphic quartz, the grains all being sub- 

 angular to rounded, and polarizing in the usual 

 vivid and brilliant colours, green, purple, blue, 

 yellow, etc. One or two small "spongy " patches 

 of a bright red colour are present, and are evi- 

 dently garnets. 



As I have made all my own slides of the Manx 

 rocks I collected, I had the opportunity of com- 

 paring their hardness. Without doubt thequartzite 

 just described was by far the hardest, and took the 

 longest time to make. It was, however, a very 

 good rock for the purpose, as, being so hard, and 

 at the same time so dense and tough, it did not 

 break during the process, but was capable of being 

 ground very thin. 



It would be a matter of interest to speculate on 

 the origin of this boulder's position. I think there 

 is little doubt that it is a " travelled " one. Very 

 probably it was brought from Scotland during the 

 Glacial period, as I am not aware of any of this 

 rock having actually been found in situ on the Isle 

 of Man. As I have already stated, the rocks at 

 Port Soderick are covered by the glacial drift or 

 "boulder clay," and very likely at one time this 

 particular boulder was in the clay covering on the 

 top of the cliffs. As these gradually wore away, 

 the block of course eventually fell to the shore, 

 and being so hard a material, is well able to resist 

 the action of the waves and weather. I found it 

 very near to the foot of the cliffs, which rather 

 tends to support my theory. 



Excursion to Peel 



At Peel the strata at the southern end of the bay 

 are the ordinary Silurian slates, but at the north 

 end an exposure of a dark-red sandstone occurs, 

 fairly dense of texture in some parts and coarse in 

 others. It shows small lenticles of impure lime- 

 stone and is accompanied by beds of conglomerate. 

 The fact that the upper layers of this series contain 

 a considerable percentage of lime would lead to the 

 inference that the Carboniferous limestone had been 

 above them, and therefore that the beds belonged 

 to the Devonian series, or were the basal beds of 

 the Carboniferous system. 



Professor Boyd Dawkins has for certain strati - 

 graphical reasons assigned them to the Permian 

 series. Mr. G. W. Lamplugh, F.G.S., is not of 

 this opinion, and I quote the following from his 

 remarks in the "British Association Handbook to 

 the Isle of Man for 1896 " : " On the whole the 

 evidence seems to me to support the view of the 

 earlier writers, that these rocks are not of later 

 date than the beginning of the Carboniferous 

 period. The strongest confirmation of this opinion 

 has recently been furnished by the boring opera- 

 tions in search of coal in the north of the island. 

 These borings have revealed the presence of a 



series of sandstones and shales intercalated with 

 the Carboniferous Limestone, and possessing, like 

 the Peel sandstone, a high dip (from 40° to 50 ), 

 which are overlain by undoubted Permian and 

 Triassic strata, lithologically unlike the Peel rocks, 

 with lew dips (rarely exceeding 5°)." 



On the top of these rocks there is a thick deposit 

 of glacial drift, and in one section I found a bed of 

 clear, sharp, yellow sand, some two feet thick. It 

 did not extend any great distance, soon thinned 

 out, and eventually disappeared. It was fairly 

 indurated, but is by no means a sandstone. It 

 could, in fact, be easily scraped away with the 

 fingernails. This bed of sand evidently represents 

 an ancient sub-littoral deposit. 



At the small fishing village of Peel there is 

 another excellent pebble beach, and I was fortunate 

 enough there to pick up two of more than ordinary 

 interest, and having made slides of each of them, 

 I will now describe their appearance under the 

 microscope. The first I picked up was a piece of 

 amygdaloidal basalt, the amygdules varying in 

 size up to about a quarter of an inch in diameter, 

 being filled with calcite. The rock is made up of 

 a ground mass containing phenocrysts and the 

 amygdules referred to. The ground mass consists 

 of small lath-shaped crystals of felspar, brown 

 patches of augite, and small flakes and cubes of 

 magnetite, the larger matter consisting of felspar 

 crystals, olivine, both fresh and slightly serpentin- 

 ized, and a small section of opaque mineral which is 

 probably titaniferous iron. Under the microscope 

 the amygdules show double refraction very strongly, 

 and cleavage too is markedly exhibited. They are 

 in some cases netted over with thin streaks of 

 greenish chlorite, and in others the chlorite occurs 

 as small irregular-shaped patches. In some 

 instances the calcite contains inclusions of magne- 

 tite, and it is noticeable that when the chlorite 

 occurs as previously referred to, the calcite does 

 not show the double refraction and cleavage nearly 

 so strongly. These vesicles are also generally- 

 lined with a thin coating of fibrous chlorite. 



Another pebble of which I made a slide was a 

 red one, containing small crystals of flesh-coloured 

 felspar, the largest in the slide being a quarter of an 

 inch long. The ground mass of this rock consists 

 of a very fine base of microlites, etc., of a reddish 

 colour, and cannot be identified as to its mineralo- 

 gical constituents. Scattered throughout this base 

 are large crystals of felspar, flakes and cubes of 

 magnetite, and also one or two sections of titani- 

 ferous iron. Amongst the large felspar crystals 

 twinning is very common, examples being observed 

 on the"Albite" system, the " Pericline " system, 

 and also "interpenetration." These crystals appear 

 to have consolidated out of a molten magma. 

 There are in addition to the felspars just mentioned, 

 sections of plagioclase (generally longitudinal) 



