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POPULAR SCIENCE REVIEW. 
ferruginous layer, common in several districts in Scotland, which he had 
obtained from the new cemetery at Arbroath. It was a thin compact layer, 
following the surface of the ground, independent of the nature of the soil, 
and forming a serious barrier to cultivation. It had never been noticed in 
systematic works, and, as far as Mr. Carruthers knew, no satisfactory expla- 
nation had been given of its origin. 
Ancient Glacier in the Pyrenees. — M. Chas. Martens, who was present 
at the meeting of the British Association, read a paper on the ancient 
glacier of the Valley of Argelez. This glacier and its affluents descended 
from the crest of the Pyrenees, whose summits now reach an altitude varying 
from 6,000 to 9,000 feet. The roots of the glacier were in the cirques of 
Gavarnie, Troumouse, Pragneres, &c., and the glacier extended into the 
plain as far as the villages of Peyrouse, Loubajac, Ade, Juloz, and Arcisac- 
les- Angles. Along the valley, polished and striated rocks, scratched pebbles, 
glacial mud, moraines, and erratic boulders, are the proofs of its existence. 
At Argelez the thickness of the glacier was about 2,100 feet, and, at the 
opening of the valley at the foot of the Pic de Geer, near Lourdes, 1,290 
feet. Between Lourdes and the village of Ade, the railway runs across 
seven moraines ; and the railway from Lourdes to Pau is cut, as far as the 
village of Peyrouse, through glacial deposits. The Lake of Lourdes is a 
glacial lake, barred by a moraine, and surrounded by numerous erratic 
boulders proceeding from the high Pyrenean mountains. Some of the 
boulders are of large dimensions : thus one of them, between the lake and 
the village of Poueyferre, is thirty feet in length, twenty-three feet in width, 
and eleven feet in height. This lake of Lourdes, surrounded by hills covered 
with briars, reminds one in many respects of the small lakes of Scotland. 
MECHANICAL SCIENCE. 
Water Supply of London. — Mr. Ormsby, C.E., has proposed a plan for 
obtaining the water-supply of London, perhaps more remarkable for its 
originality than for its practicability. Starting from the idea that all water 
which has passed through strata of earth is more or less contaminated, ®Mr. 
Ormsby proposes to construct non-absorbent receiving beds, by which' the 
entire rainfall will be collected in the same condition of purity as when it 
reaches the earth. “ The arrangement of the collecting surfaces may be 
illustrated by a chess-board, where each square would represent a collecting 
basin, the centre of which would be two feet lower than the sides. The 
lines between those squares would represent walls 12 inches thick, 'built 
about 2 feet high, and filled in behind with earth to such a height as to 
admit a bed of concrete being laid upon it, so that its upper surface may slope 
from the edge of the wall to the centre of the basin. Upon this bed of concrete, 
Bangor or other equally good and durable slates are proposed to be laid, set 
in cement ; and when this is done, the waterworks are completed, so'that the 
jsntire rainfall will immediately flow off into the central pipe or chamber 
which communicates with the receiving reservoir.” Thus, in place of being- 
driven to the sources of the Severn or Thames, or to the lakes of Westmore- 
land, for his supply of water, Mr. Ormsby would erect his collectingNbeds 
