IV. COMPASSES. 781 



every five minutes, the clock giving the exact time lor 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. 



3099a. Portable Compass. Colonel Degen, Bobruisk. 



3151. Azimuth Compass, by Brauer. 



T. Brauer, St. Petersburg. 



3155aa. Bronze Compass taken from a wrecked Japanese 

 junk. Capt. Murray -, per F. Buckland. 



3151d. Floating Mariner's Compass. 



Dumoulin Froment, Paris. 



3151e. Eclimetre for floating compass forming a spherical 

 spirit level for quick elevation. Dumoulin Froment, Paris. 



3151k. Dipping Needle and Compass used by Captain 

 Cook during his voyage round the world. 



Royal Naval Museum, Greenwich. 



' 31511. Chinese Compass, from a collection made by Mr. 

 Coryton, Barrister-at-law of the Temple. 



Royal Naval Museum, Greenwich. 



3151m. Symon's True North Compasses, with improved 

 indicator arranged to show the True North instead of the Mag- 

 netic North as usually shown. L. Casella. 



31 5 In. Coloured Compass Cards. Max. Raphael, Breslau. 



315 lo. Mica-plates for uncoloured Compass Cards. 



Max. Raphael, Breslau. 



For the manufacture of compass cards, mica is now exclusively used. The 

 advantage to be derived from its use consists in the greater facility with 

 which the magnetic needle can be fixed, the transparency of the card, its 

 non-conductivity for electricity, its lightness and indifference to ordinary 

 changes of temperature, its durability, &c. 



3151p. Compass, Hart's. M. Breguet, Paris. 



3151q. Patent True Course Finder. W. H. Roberts. 



The object of this instrument is to avoid arithmetical calculation in finding 

 the true course from the compass or magnetic course, with corrections for 

 lee-way, deviation, and variation. This instrument will give by three move- 

 ments of the index the true course to fifteen minutes. The outer rim of the 

 dial is accurately divided into degrees, and the inner rim into points, points, 

 and points. The index has two arcs, A and B, and moves freely on a 

 pivot, C. The arc A indicates the points, points, and \ points. The arc 

 B is so made that its centre line will point to the exact number of degrees 

 which are contained in the number of points shown by the arc A. The arc B 

 has also a vernier, by which the observer can read off to of a degree. On 



