Railroad Engineers' Field-book and Explorers' Guide: Especially Adapted to the Use of Railroad Engineers on Location and Construction, and to the Needs of the Explorer in Making Exploratory Surveys
J. Wiley & sons, 1890 - 358 Seiten
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Seite 234 - Nitric acid will produce a black spot on steel ; the darker the spot the harder the steel. Iron, on the contrary, remains bright if touched with nitric acid. Good steel in its soft state has a curved fracture and a uniform grey lustre ; in its hard state, a dull, silvery, uniform white.
Seite 232 - ... uniform color. If the top has a regular, rounded form ; if the bark is dull, scabby, and covered with white and red spots, caused by running water or sap, — the tree is unsound. The decay of...
Seite 247 - ... out the object-glass, so as to bring the vertical wire upon an object as near as the range of the telescope will allow. Having this clearly in mind, unclamp the limb, turn the instrument half-way around, reverse the...
Seite 248 - When both wires in succession have been thus treated, the line of collimation is adjusted on the near object, and the telescope again brought upon the most distant point ; here the tube is again revolved, the reversion of the wires upon the object once more tested, and the correction, if necessary, made in the same manner. He proceeds thus until the wires will reverse upon both objects in succession ; the line of collimation will then be in adjustment at these and all intermediate points, and by...