[ ]

[ 48]Mining Journal, 1864, vol. 34, p. 478

[ ]

[ 49]The Engineer, 1861, vol. 12, p. 189

[ ]

[ 50]Ibid., p. 78

[ ]

[ 51]Mushet, op. cit. (footnote 46), p. 9

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[ 52]Ibid., p. 25