d section reaches to this type of shutter as applied to modern cameras. The leaves of the Iris diaphragm slide within a fixed was in the latter part of 1896, and from that time until from the second air-lock to the working face. The diaphragm located in the axis of the ray of light and 1902, when… … vicinity, who are strictly re- up, the workmen are able to pass liable. forward of the shield and drill — “ bars al The dam in question was dis- and blast out the rock below it. covered about two years ago, by This work is unique in horizon- tal shield excavation, and so far a farmer living near…
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