formed by the water. It is composed of
tufa, carbonate of lime, and was formed in the same manner as
stalactites and stalagmites are formed. As the water flowed over the
logs, the evaporation of a portion of the carbonic acid gas caused the
separation of an equivalent quantity of insoluble carbonate of lime,
which, layer by layer, built up the mound. A fragment of the rock
which I possess contains leaves, twigs, hazel nuts, and snail shells,
which, falling from time to time upon it, were incrusted and finally
imprisoned in the stony mass.

[Illustration: SECTION OF HIGH ROCK]

Analysis of a Fragment of the Rock

Carbonate of lime 95.17
Carbonate of magnesia 2.49
Sesquioxide of iron 0.07
Alumina 0.22
Sand and clay 0.09
Organic matter 1.11
Moisture 0.39
Undetermined 0.46
------
100.00

"Below the rocks the workmen followed the spring through four feet of
tufa and muck. Then they came to a layer of solid tufa two feet thick,
then one foot of muck in which they found another log. Below this were
three feet of tufa, and there seventeen feet below the apex of the
mound they found the embers and charcoal of an ancient fire. By whom
and when could the fire have been built? The Indian tradition went
back only to the time when the water overflowed the rock. How many
centuries may have elapsed since even the logs were placed in their
position? A grave philosopher of the famous watering-place,
remembering that botanists determine the age of trees by counting the
rings on the section of the stems and noticing the layers in the tufa
rock, polished a portion of the surface, and counted eighty-one layers
to the inch. He forthwith made the following calculation:

High Rock, 4 feet 80 lines to the inch 3,840 years
Muck and tufa, 7 feet low estimate 400 "
Tufa, 2 feet 25 lines to the inch 600 "
Muck, 1 foot 130 "
Tufa, 3 feet 900 "
-----
Time since the fire was built 5,870 "

"As I have seen half an inch of tufa formed in two years on a brick
wh