12,238. Marks, E. C. R., [Dyer, R. E. H.]. May 18. Range-finders of the type described in Specification 4227/09, and having reflecting-means on the base-bar are provided with a pair of telescopes which receive rays of light from the reflecting-means, the range being read off when the observer looks through the telescopes. Two telescope tubes a, b forming a short-base are arranged side by side, and carry eyepieces h, i at one end and a reflecting-prism c at the other. The object lenses f, e are mounted in the same housing d that carries the prism c. Reflecting- prisms l, o are mounted on platforms j, k arranged at opposite ends of the base. To measure a range, the instrument is alined on an object and adjusted until the image observed in one telescope coincides with the infinity line of a range scale described in Specification 27,022/08. engraved on a glass disk placed in the focal plane. The object is then observed in the other telescope, and the range read off on the corresponding scale. Both telescopes are provided with range scales, and provision is made for turning the prisms l, o through a right-angle and thus allowing an object on the other side of the instrument to be ranged. This end may also be achieved by turning the base-bar &c. upside down, and in this case one of the range scales is marked upside down. The prisms are mounted so that they may be adjusted horizontally and vertically. The platforms carry rings 20, Fig. 7<a>, positioned by lugs 23 engaging with stops 21, 22. The prism is mounted on a plate 26 carried by a turntable 25 rotatable relatively to the ring 20 and limited by a pin 30 working in a slot 31. The prism can be tipped by adjusting pointed 'screws 28, 29, 30 which bear on the turntable 25. In a modification, the plate 26 is hinged to the turntable, and only one adjusting-screw is used. In another form of instrument, a plain base-bar is used with telescopes at one end, the images being directly reflected to the telescope by prisms on the bar. In another modification, a single movable prism 42, Fig. 13, is used in conjunction with a fixed reflecting- device 44 in front of the auxiliary telescope 43. In another modification, a long telescope is obtained by adding the prism 44, which reflects light to the additional tubes 46. The base-bar is supported at one end by a cradle p pivoted at q to a member r rotatably mounted on a tripod stand s. At the other end, pins 12, 13, Fig. 3, on the base-bar engage with slots in a cradle 15. A nut 16 works the screwed end of the pin 13, so that the base-bar may be adjusted horizontally by operating the nut 16 against the action of a spring 17. The cradle 15 is pivoted at 7 to a carriage x, and may be adjusted by a worm and worm-wheel 9. The carriage x is adjustably mounted on a second carriage 2, which is itself slidable along a bar t of the tripod stand u. Means are described in the Specification for effecting a virtual lengthening of the base by swinging the base-bar relatively to the carriage x.