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HISTORY AND PROGRESS

enough that the bearing be such, that the mils areall in the same plane when the stones on whichthey rest are in good order, or in their properposition, parallel with the line of the road : theparallelism of the rails should be preserved,when, by the yielding of the ground, or fromany other cause, the stones are displaced fromtheir proper position, and they are made toform a considerable angle with the line of theroad. It would not have been necessary tohave been thus diffuse on this point, had Inot found that several, even of the most modernforms of chair, were evidently formed contraryto this principle: — many, with a view ofcausing the mode of joining to keep the sup-port or stone in its proper position, rather thanallowing it to adapt itself to the unavoidableyielding of the ground on which it rests, orparallel with the rail: but the least considera-tion will evince the futility of this, especiallywhen the yielding of the ground causes thestone to rest entirely on one side; it will atonce be seen, that when the carriages comeupon the rails, something must yield andgive way, by the great strain thrown uponthe fastening from the oblique action of theweight.

About twenty years ago, malleable ironrails were tried at YVallbottle Colliery, near