III. MISCELLANEOUS. 631 



309 9b. Normal Compass of the Imperial German Navy, 

 with stand, diopter- apparatus, two compass-cards, &c. 



Carl B amber g, Berlin. 



The normal rose A. of the normal compass is arranged for reversal so that 

 at any time a determination of the error of collimation of the zero-line to the 

 axis of the needle may be effected, and we are enabled to make a deter- 

 mination of the collimation of other roses of ordinary construction, but of the 

 same diameter, by comparison. For measurements on land the gimbals may 

 be fixed and the compass itself be brought to a horizontal position by means 

 of screws. 



3O99c. Boat's Compass, with equipments in order to be 

 employed as a email azimuth compass. Carl Bamberg, Berlin. 



The case of the boat compass serves for its transport, and also (by the 

 removal of two pieces) as a binnacle. In combination with the dioptric ap- 

 paratus and the stand, the boat compass is a small, handy, and accurate 

 azimuth compass. 



3O99d. Boat's Fluid Compass. Carl Bamberg, Berlin. 



The rose of the fluid compass is furnished with a float, so that pressure, 

 and therefore also the friction on the pivot, are reduced to a minimum. The 

 cap and pivot are made of ruby, so that they do not easily wear, and a stop 

 becomes unnecessary. 



3099e. Albini's Registering Steering Compass* 



Elliott Brothers. 



The instrument consists of a steering compass, with clock and apparatus 

 attached, for printing on a slip- of paper the direction of the ship's course 

 every five minutes, the clock giving the exact time for eight days without 

 winding. An instrument of this description placed in the captain's cabin 

 would thus enable him to have a record of a whole voyage. 



3099f. Prismatic Compass, with improvement of ring to 

 hold more safely in the hand. Henry Porter. 



3100. Photograph of a Base Measuring Apparatus, 



in course of construction for the United States Lake Survey, 

 Detroit. A. Repsold and Sons, Hamburg. 



Base-measuring Apparatus. A measuring rod 4 metres iu length is used, 

 consisting of a steel and a zinc rod, enclosed together in a wide iron tube, 

 and with divisions upon platinum at the ends. The measuring rod rests 

 on its extremities (below the divisions) upon its supports, by which the 

 advantage is attained that the support remains the same for; two positions, and, 

 therefore, only one has to be arranged for each new position. Before making 

 a measurement microscopes are placed, at a suitable level, upon separate 

 supports above the rod-supports, and beneath these the rod is carried forward. 

 To set off the daily termination a cylinder is arranged, by level, perpendicu- 

 larly under the last microscope on the small hemisphere of one terminal plate, 

 by the microscope a division on the upper terminal surface of the cylinder is 

 read off in the two positions differing by 180. The apparatus is accompanied 

 by a comparator for the comparison (1) of the measuring rod with a standard 

 metre ; (2) of the measuring rod with a spare measuring rod. In the first 

 casa the standard metre is laid, together with the measuring rods, upon a 



