MISCELLANEOUS COMMUNICATIONS. 341 



operation, as they often rest on rugged beds, and these not always of much 

 inclination. He proposed a very ingenious explanation of their movement 

 by means of hydrostatic pressure, arising from the fact of the lower part of 

 the glacier being of a higher temperature than the upper: this causes a melt- 

 ing of the under part, and a consequent raising of the mass in a perpendicu- 

 lar direction to the earth's surface, while its descent was at right angles to 

 the inclined surface : a progressive moiion downwards ensues, following the 

 law of the resolution of forces. He then spoke of certain causes of the rents 

 and fissures in glaciers, these being often convex downwards, owing to the 

 operation taking place in the middle part of the mass, which descends soon- 

 est, while the whole is held in its place by the upper and lower extremities : 

 also tubular fissui'es are formed by blocks of stone sinking by degrees in the 

 glacier, owing to their higher temperature gradually melting the surrounding 

 ice. He then alluded to the singular accumulations of detritus on the gla- 

 ciers, which are locally termed moraine, and are formed by eboulemenh in win- 

 ter, and covered by the snow. These he found to assume linear directions 

 parallel to the axis of the glacier ; and, from the regularity of their arrange- 

 ments, he conceived it possible to discover the site of old glaciers from the 

 moraine which had remained on the ground after their destruction. 



Encroachments of the Sea It is well known that the Baltic Sea, 



generally speaking, makes inroads upon the surrounding shores ; but there 

 was an idea that Prussia resisted these. The researches of M. Domeyko, a 

 Polish gentleman, have, however, proved that this country has shared the 

 general fate to such an extent as to lose a whole province on the borders of 

 the Gulph of Konigsberg. Voight, a German writer, and other still more 

 ancient authors, all record that, at the time when Prussia was occupied by 

 the Teutonic order, the province of Vitlandia was granted by them to the 

 inhabitants of Lubeck. But every trace of this territory has now disappear- 

 ed ; it was situated between Billau, Brandebourg, and Balga. Pisanski, in 

 his work on the Baltic Sea, says that the waters constantly advance on the 

 western coast, as well as on the northern coast of Samland ; and there is a 

 tradition among the people that some long strips of land, formerly covered 

 with forest, have been thus buried. In fact, the waves still throw up trunks 

 and roots of trees which evidently came from their own soil, now at the bot- 

 tom of the sea. The ruins of the chapel of Saint Adalbert, formerly six miles 

 from the sea, are now scarcely one hundred paces distant. 



Geology — M. Tournet has presented a long memoir to the French Aca- 

 demy of Sciences, containing his geological observations in the neighbour- 

 hood of A rbresle ; in these he establishes some well-determined affinities 

 between the nature of those rocks which are known to have pierced through 

 the upper crusts at various periods, as well as their direction, the soil which 

 covered them, and their degree of fusibility, as connected with the period of 

 eruption. M. Tournet thinks that the true and only primordial sedimen- 

 tary rock is composed of clay slate, and that this rock, which contains the 

 element of mica, being altered or modified in different manners, has been 

 transformed into gneiss, mica slate, and other substances. He admits four 

 modes of alteration : one is calcination, a second trituration, a third the 

 changes produced by penetration and crmmtallon, and the fourth is the in- 

 fluence of the granite, which transforms it into gneiss by introducing its 

 fcldspalli when in a state effusion. 



