1853.] OF THE ROYAL INSTITUTION. 329 
WEEKLY EVENING MEETING, 
Friday, June 3. 
Tae Duxe or NortuumBer.Anp, K.G., F.R.S., President, 
in the Chair. 
Dr. Joun Trynpatt, F.R.S. 
On some of the Eruptive Phenomena of Iceland. 
Tue surface of Iceland slopes gradually from the coast towards the 
centre, where the general level is about 2000 feet above the surface of 
the sea. On this, as a pedestal, are planted the Jékull or icy mountains 
of the region, which extend both ways in a north-easterly direction, 
_ Along this chain the active volcanoes of the island are encountered, 
and in the same general direction the thermal springs occur, thus 
suggesting a common origin for them and the volcanoes. From the 
ridges and chasms which diverge from the mountains mighty masses 
of steam are observed to issue at intervals, hissing and roaring, and 
where the escape takes place at the mouth of a cavern and the 
resonance of the cave lends its aid, the sound is like that of thunder. 
Lower down in the more porous strata we have smoking mud pools, 
where a repulsive blue-black aluminous paste is boiled, rising at times 
into huge bladders, which on bursting scatter their slimy spray 
toa height of fifteen or twenty feet. From the base of the hills 
upwards extend the glaciers, and on their shoulders are placed the 
immense snow-fields which crown the summits. From the arches 
and fissures of the glaciers, vast masses of water issue, falling at 
times in cascades over walls of ice, and spreading for miles and 
miles over the country before they find definite outlet. Extensive 
morasses are thus formed, which lend their comfortless monotony 
to the dismal scene already before the traveller's eye. Intercepted 
by the cracks and fissures of the land, a portion of these waters is 
conducted to the hot rocks underneath; here meeting. with the 
volcanic gases which traverse these underground regions, both travel 
together, to issue at the first convenient opportunity either as an 
eruption of steam or as a boiling spring. 
The origin of the water which feeds the springs is here hinted at. 
That origin is atmospheric. The summits of the Jékull arrest and 
mix the clouds, and thus cause an extraordinary deposition of snow 
and rain. This snow and rain constitute the source from which the 
springs are fed. The nitrogen and ammonia which occur, without 
exception, in every spring, exactly as we find them in rain water, 
furnish the proof of this; for the known deportment of these 
AA 
