JOHNSTOWN. The material of the work was clay or silt apparently most excellent material if properly used. It was of such nature as to form a thoroughly impervious barrier terior surface. In the core of the structure a row of sheet piling could be seen which had been used in the original construction but which added very little to its strength. The material exhibited marks of stratifi cation showing what miners would call ' stopes ' or Steps upon the sides of the crevasse. At the eastern end the regular spillway or overflow was placed. This is a sluice or canal cut through the rock about forty
JOHNSTOWN. The material of the work was clay or silt apparently most excellent material if properly used. It was of such nature as to form a thoroughly impervious barrier terior surface. In the core of the structure a row of sheet piling could be seen which had been used in the original construction but which added very little to its strength. The material exhibited marks of stratifi cation showing what miners would call ' stopes ' or Steps upon the sides of the crevasse. At the eastern end the regular spillway or overflow was placed. This is a sluice or canal cut through the rock about forty feet wide with its bottom eight or ten feet below the top of the dam. It was crossed by two bridges and some idea of its size can be derived from the evident length of the one shown in perspective. A fish screen to prevent the fish from escaping crossed the channel but as it was only three feet high it could not have greatly impeded the water. It is not now in place be ing broken and destroyed. It is quite possible that it was carried away before the overflow began. Five ter ran through the base of the dam terminating in masonry tunnels reaching well outside of the base. house for these pipes is shown in one of the cuts. On top of the gate house at the foot of the inner slope of the dam as shown in one of our views there was ori ginally a wooden tower containing appliances for opening and closing the gates. This tower was carried to oigy a few feet above the water level and was reached only by boat. After a former break in the dam some years ag this tower was burned and when the dam was rebuilt this central outlet was permanently closed. Some of the charred timbers remaining from this tower are still to be seen around what remains of the old gate house. The same illustration gives a sectional view showing the comparative area of the regular spillway but which is located on the other end of the dam from that shown in the same view. The following details of the overflow and colla
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