. Annual report of the commissioners on the Troy and Greenfield and Hoosac Tunnel : together with the reports of chief and consulting engineers . e it conform more nearly to the rock section, the formwas modified as shown in the diagram. Afterwards, under a suggestion from George Berkley, C. E.,who was familiar with workings in the London clay, the formwas still further modified, and that part east of the 174 feet,or beneath ground will be of the shape indicated in DiagramNo. 3. This masonry is built of brick, and through the 174 feet it isfrom five to eight courses or rings in thickness,
. Annual report of the commissioners on the Troy and Greenfield and Hoosac Tunnel : together with the reports of chief and consulting engineers . e it conform more nearly to the rock section, the formwas modified as shown in the diagram. Afterwards, under a suggestion from George Berkley, C. E.,who was familiar with workings in the London clay, the formwas still further modified, and that part east of the 174 feet,or beneath ground will be of the shape indicated in DiagramNo. 3. This masonry is built of brick, and through the 174 feet it isfrom five to eight courses or rings in thickness, increasingtowards the east; eight rings give a thickness of 32 inches. The large expense heretofore incurred on this part of thework, brought it at length into a state in which it seemedbest to begin full size tunnel and line it with masonry. As before remarked, the removal of the quicksand fromoverhead, the making and maintaining of surface ditches, andthe driving of the heading, had so far restored the morals ofthe rotten rock, by taking away the water, that the contractorfound it comparatively easy to do his work. He also found Diagram N? 2. / / Stale 10 feel to I inch Diagram N?3. /
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