| 释义 |
spider-line
Also spider's line.
[spider n.]
One of the threads or filaments of spider-web used to form the reticle of various optical instruments, esp. of micrometers, and serving to obtain minute measurements; also loosely, any slender thread or wire used for this purpose.
1829W. Pearson Pract. Astron. II. 323 The spider's lines, or wires, are usually paid parallel to one another on a circular plate of brass. 1866Parkinson Optics (ed. 2) 209 Such a set of threads are commonly called cross-wires or spider lines. 1888Rutley Rock-Forming Min. 14 Within the focus of the eye-glass, two fine wires or spider-lines are inserted.
attrib.1829W. Pearson Pract. Astron. II. 245 Binocular Spider's-line and Glass-disc Micrometers. 1875Knight Dict. Mech. 1431/1 A substitute for the spider-line micro⁓meter. |