332 ; NOTICES OF THE MEETINGS [June 3, 
In process of time, however, the heat retires to greater depths, 
the sources of the sulphurous acid and sulphuretted hydrogen become 
by degrees exhausted, and at such places the acid reaction of the 
soil disappears. Carbonic acid is found in abundance everywhere, 
but as long as the more powerful sulphuric acid is present the former 
must remain free. But when the acid reaction has disappeared, 
the carbonic acid combines with the alkaline bases, the bicarbonates 
thus formed impregnate the thermal waters, and become solvents 
for the silica which. these waters are known to contain in such sur- 
prising abundance, and which, as we shall presently see, furnishes 
the materials for the wonderful architecture of the Geisers. 
Casting our thoughts back upon the foregoing description, the 
hypothesis of internal heat will be seen to be implied, and from this 
as a cause we have deduced the various chemical phenomena as con- 
sequences. Holding fast by experiment, we see that the various 
gases whose existence has been urged as one of the strongest proofs 
of the so called chemical theory, follow in the most natural and 
necessary manner from the rival supposition. Given the heat and 
the materials the results are such as any chemist acquainted with 
the reactions might predict @ priori. By the labours of a chemist 
indeed a new and wonderful light has been thrown upon the entire 
volcanic phenomena of Iceland. With implicit reliance on the appli- 
cability of his science to the solution of these phenomena, he has 
travelled side by side with nature, combined her conditions, and 
produced her effects. Basing all his reasoning upon experiment, 
he ‘has given to his conclusions a stability which mere speculation, 
however plausible, could never claim. That chemist is Bunsen, to 
whose researches in Iceland the audience were indebted for the 
materials of the present discourse. 
The Lecturer then adverted to the Geisers; and proposed, as his 
time was limited, to confine his attention to the Great Geiser. We 
have here a tube ten feet wide and seventy feet deep ; it expands at its 
summit into a basin, which from north to south measures fifty-two 
feet across, and in the perpendicular direction sixty feet. The interior 
of the tube and basin is coated with a beautiful smooth plaster, so 
hard as to resist the blows of a hammer. The first question that 
presents itself is, how was this wonderful tube constructed? How 
was this perfect plaster laid on? A glance at the constitution of 
the Geiser water will perhaps furnish the first surmise. In 1000 
parts of the water the following constituents are found: — 
Silica F 5 . - 0.5097 
Carbonate of Bada ‘ ‘ . 0.1939 
Carbonate of Ammonia p - 0.0083 
Sulphate of Soda ; ; 021070 
Sulphate of Potash . : - 0.0475 
Sulphate of Magnesia : . 0.0042 
Chloride of Sodium . < O52 
