Knight's American mechanical dictionary : a description of tools, instruments, machines, processes and engineering, history of inventions, general technological vocabulary ; and digest of mechanical appliances in science and the arts . ili. Jacobs Ladder. (Xaii-tienl.) A rope ladderwith wooden rounds. Jacobs Staff. 1. An for taking al-titudes, having a brass circle divided into (our eijualparts by two diametric lines. At each extremity isa perpendicular riglet over the lines, with a hole be-low each slit for discovering objects. The cross ismounted on a staff. A cross-sto{f. 2. (S
Knight's American mechanical dictionary : a description of tools, instruments, machines, processes and engineering, history of inventions, general technological vocabulary ; and digest of mechanical appliances in science and the arts . ili. Jacobs Ladder. (Xaii-tienl.) A rope ladderwith wooden rounds. Jacobs Staff. 1. An for taking al-titudes, having a brass circle divided into (our eijualparts by two diametric lines. At each extremity isa perpendicular riglet over the lines, with a hole be-low each slit for discovering objects. The cross ismounted on a staff. A cross-sto{f. 2. (Siirvci/ing.) An instniinent (a. Fig. 2710)used to measure distances and heights. It has asquare rod, with a cross or cursor, which has a setscrew to keep it in position on the rod when re-quired. The rod is three or fo\ir feet in length, anddivided into four or five eipial parts. The cursorhas a siiuare socket and slips on the staff; its lengthis equal to one of the divisions of tlie staH. Theinstrument is mounted on a tripod when in use, thecursor being in the plane of the horizon when meas-iiring distances, and vertical thereto when measuringbights. ?rhe cursor is adjusted on the rod to the second JACONET. 1210 Jacobus Sca^, division, andtlie olwervationtaken friiinsuch a positionthat the iliree-tion of the statfbisects tlie an-gle subtendedby a line drawnII H between the r^ two Retire or ad- vance with tlieinstrument un-til from the sta-tion )ii the vis-ual line fromm passing to cd will touchthe ends c fof the a jiicketat Hi. Slip thecursor on to thethird divisionof the statf andretire till froma new station nthe visual raysfrom thence willreacli the sameobj ec t s, c (/touching c f asThe distance between the before. Drive a [ is eipial to the distance between the is but one illustration of its application. SeeCresys Encyclopedia Civil Engineering, edition1865, pp. 832-835. 3. A straight rod h shod with iron, an
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