TY - JOUR
AB - THE optical principles involved in gun-sighting apparatus, described in the issue of NATURE for January 9, 1902 (p. 226, vol. lxv.), have been further developed by Sir Howard Grubb, F.R.S., and applied to some new forms of geodetical instruments. In the gun-sighting apparatus alluded to, a virtual image of an illuminated cross is optically projected on to the object aimed at, and both the cross and the object are easily seen without any refocussing or straining of the eyes. In the case of the gun sights and also the present instruments, light traverses a plate of glass coated with a very thin film of galena; by this means reflection of light from the surface of the glass is greatly increased, while but little transmitted light is shut off. The process of depositing galena is due in the first instance to Prof. J. Emerson Reynolds, F.R.S.; it is described in the Proc. Chem. Soc. for 1884, under the heading “The Synthesis of Galena by means of Thiocarbamide.”
TI - Some New Forms of Geodetical Instruments
JF - Nature
DO - 10.1038/066276a0
DA - 1902-07-17
UR - https://www.deepdyve.com/lp/springer-journals/some-new-forms-of-geodetical-instruments-nmXY0x05mq
SP - 276
EP - 277
VL - 66
IS - 1707
DP - DeepDyve
ER -