“Just below the mound were found four logs, two of which rested upon the other, two at right angles, forming a curb.  Under the logs were bundles of twigs resting upon the dark-brown or black soil of a previous swamp.  Evidently some ancient seekers after health had found the spring in the swamp, and to make it more convenient to secure the water had piled brush around it, and then laid down the logs as a curb.  But you inquire, how came the rock, which weighed several tons, above the logs?  The rock was 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 which received the overflow from a spout of water containing only twenty grams of carbonate of lime in a gallon, I am inclined to think our antiquarian’s estimates are not entirely reliable."[A]