The Merjelen or Maerjalen Lake, situated at an altitude of 2367 metres (7750 ft.) above sea-level at the western flank of the Great Aletsch glacier, belongs to the class of glacier lakes which are found in depressions or valleys barred by glaciers whose direction of flow is more or less at right angles to the same. Like the majority of glacier lakes, it has the shape of an irregular triangle, the length being about 1.5 kilometre (nearly a mile), its greatest width 0.5 kilometre (550 yards), and its mean depth 28 metres (92 ft.). Hence its superficial area amounts to 375,000 square metres (438,000 square yards), and its volume at high-water level to about 10 million cubic metres or tons.

It is a noteworthy fact that, although Alpine glaciers have, during the last few years, not shown any very marked oscillations, the Central Alps have, since the year 1892, been annually visited by a disaster caused, directly or indirectly, by the bursting or falling of a glacier. Thus, in 1892, the Tête Rousse glacier of the Mont Blanc group swept away the Baths of St. Gervais; in 1893, the village of Taesch, between Viess and Zermatt, was devastated by the torrent of the Weingarten glacier, not far from the village of Randa, which was destroyed by a glacier avalanche in the year 1819; again, in 1894, the torrent of the Crête glacier (Grand Combin group, Rhone valley) suddenly poured its flood into the river Dranse, and thereby endangered the town of Martigny; while last year the record was swelled by the avalanche of the Altels glacier on the north side of the Gemmi Pass, in the Bernese Oberland.

The physical conditions under which the Old Red Sandstone of Scotland was formed is a subject that has long occupied the attention of many of our leading geologists, from the time of Hugh Miller and Sir Roderick Murchison down to those of the present day. It has been variously regarded as of fresh-water and marine origin, as having been thrown down in lakes and in the open sea, or in inlets of the latter. But as yet the whole matter seems to remain an open question, which the unique physical and palæontological elements of the formation make difficult of solution.

The genus Cheirurus offers an interesting study in evolution. Barrande, in his monumental work on the Silurian System of Bohemia, drew up a classification of the genus based principally on the character of the pleural grooves. Thus he divided the species into two sections—