234 Intelligence and Miscellaneous Articles. 
to be inapplicable, on account of its resting on important errors in 
matters of fact, and wanting other facts which had been ascertained 
since Saussure’s researches were published. 
The author next proceeded to explain the following theory, which 
he thought capable of including all the phenomena as yet known. 
During winter glaciers repose on their inclined beds in a condition 
of perfect rest. When warm weather arrives the atmospheric tem- 
perature rises above 32°Fahr. The joint action of the air, rains and 
the solar rays, melts the ice and snow at the surface of the glacier. 
Part of the water finds its way by the crevices to the glacier bed, 
and there acting on the ice fits it for motion, Another part at the 
same moment percolates the spongy ice, and incorporating with its 
structure impresses the property of mobility on its parts and mole- 
cules. The whole mass of the glacier is now ina condition to obey 
the ordinary laws of fluids. It descends the mountain side like any 
other semi-fluid, by the action of gravity, and perhaps the head press- 
ure of the Nevé. When the supply of water is diminished by cold 
its progress is also diminished. When the supply is increased by 
heat its progress is also increased, and that as a necessary conse- 
quence of the function which the water performs. The glacier is 
consumed by the melting of its surface and lower extremity, and its 
level preserved by molecular movements within it, just as in the case 
of other fluids in channels. 
When the summer and autumn are gone, the temperature of the 
air falls to the freezing point or below it, the melting of the surface 
ceases, the supply of water to the spongy structure of the glacier is 
cut off; it loses its property of molecular motion, it ceases to be a 
semi-fluid, it becomes rigid, and its weight and friction afford 
effectual resistance both to the action of gravity and to the head 
pressure of the Nevé from the winter snows; it returns to its state 
of perfect rest, and there it remains till next summer’s heat melts its 
surface and affords water, which is its pabulum of motion. The hy- 
drostatic pressure of the water in the ice is an element which very 
probably acts an important part in these phenomena, both by ex- 
erting its force and by its separating the molecules of the ice toa 
greater distance, and so increasing its analogy with fluids. 
The author concluded by stating, that he put forth this theory 
rather as a basis for future investigations than as an absolute truth. 
All the facts already known he considered to be capable of being 
brought under it, and the investigations at present in progress would 
very soon prove it correct or otherwise. 
XXXIX. Intelligence and Miscellaneous Articles. 
ON THE DISCOVERY OF NATIVE LEAD IN IRELAND. BY MR, 
T. AUSTIN, JUN. 
To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, 
A® the existence of lead in its native state has been deemed pro- 
blematical by our most eminent mineralogists, it may not be un- 
