39 



Quick Leveling Attachment. 



[For illustration see elsewhere. ] 



As all devices of this kind detract more or less from the stability of an instru- 

 ment, it seems they never have been regarded with much favor by the engineering 

 profession at large. There are cases, however, where the use of such a device, in 

 a mountainous country, or in underground work of a close character, becomes very 

 desirable. Messrs. C. L. Berger & Sons' device, unlike devices of a similar kind form- 

 ing a part of the instrument proper, consists of a coupling with a ball and socket joint 

 which can be screwed between the instrument and tripod. As this intermediate 

 piece forms no part of the instrument itself it can be readily attached or detached 

 at will, thus adapting the instrument to the circumstances and to the class of work 

 in hand. For this purpose the threads of this coupling or quick-leveling attach- 

 ment, and those of the instrument and tripod are identical ; and as all their transits 

 and levels with four leveling screws are interchangeable on any of their tripods, 

 one such coupling is sufficient for an engineer's outfit. In fact one extra tripod 

 permanently provided with this quick-leveling attachment may be kept ready for 

 occasional use in an office where there are a number of their instruments. 



To use this quick-leveling attachment proceed as follows: Screw it to the 

 instrument, and then screw both to the tripod in the usual manner, taking care 

 that the coupling becomes firmly fastened thereto. Now to operate it, slightly 

 unscrew the instrument from its hold upon the flange of the coupling by means of 

 the milled edges provided for this purpose, and move it approximately into a level 

 plane, then again screw the instrument firmly to the coupling same as before. 

 This being accomplished, move the instrument over the given point on the ground 

 by means of the centering arrangement described later on, and level up carefully 

 by the leveling screws alone. It will be seen that this quick-leveling attachment 

 is operated entirely independent of the leveling screws or centering arrangement. 

 Of course, when this device is to be used for several days in succession, it is not 

 necessary to detach it from the tripod every time the instrument is to be removed. 

 In such cases the instrument only should be detached from the coupling. When- 

 ever it becomes desirable to detach the coupling from the tripod, it can best be 

 performed by allowing the instrument to remain fastened to the coupling, then by 

 taking hold of the milled edge of the coupling unscrew in the usual manner. In 

 cases where the coupling has been permanently attached to a tripod, the small 

 screws connecting it to the tripod head must first be removed, 

 i To secure the greatest possible stability to the instrument, the outside diameter 

 of the hollow hemisphere is equal to the distance between the leveling screws of 

 the instrument; and to secure a smooth and ready action, leather washers are 

 provided in the socket which act against the hemisphere. However, when the 

 instrument is clamped to the flange of the coupling these washers recede, and the 

 metal surfaces are brought into direct contact with each other. 



The Oradienter Screw. 



This very convenient attachment consists simply in a screw working against 

 the clamping arm suspended from the horizontal axis, and on the opposite side 

 from the vertical arc. A strong spiral spring is set directly opposite the screw, 

 and presses the clamp arm against the end of it. This screw is cut with great care 

 in a lathe. It has a large silvered head graduated into fifty equal parts. As the 

 screw is turned, the head passes over a small silvered scale, so graduated that one 

 revolution of the screw corresponds to one space of the scale. 



Obviously then, the number of whole revolutions made by the screw, in turning 

 the telescope through a vertical arc, can be ascertained from this scale. The clamp 

 arm of the telescope has its clamping screw just above the horizontal axis, in the 

 usual manner. When this screw is free, the telescope may be revolved ; but when 

 it is clamped, the telescope can only be moved by the gradieiiter screw, which thus 

 takes the place of th ordinary vertical tangent screw. The screw is cut with such 



