4 



DAMASCUS BLADES 



598 



described by Daguerre. This mercurial box consists of a box mounted on legs, 

 having a close-fitting cover A, and an iron bottom in which is placed the mercury c, 



with a small thermometer F to indicate the proper 

 temperature, o is a piece of glass let into the 

 side of the box through which the Daguerreotype 

 plate H, fixed in the frame n, can be seen. D is 

 a spirit-lamp, and i the platform on which it 

 stands. The subject is eventually fixed by the 

 use of hyposulphite of soda, which removes the 

 bromo-iodide of silver and leaves a picture pro- 

 duced by the contrast between a combination of 

 the silver and mercury, and the surface of the 

 unchanged polished silver. 



The application of chloride of gold to the 

 finished picture was introduced by M. Fizeau. 



Chloride of gold applied to the picture has 

 the effect of fixing and enlivening the tints. A 

 small grate being fixed by a clamp to the edge 

 of a table, the plate is laid upon it with the 

 image uppermost, and overspread evenly with 

 solution of chloride of gold, by means of a fine 

 broad camel-hair brush, without letting any 

 drop over the edge. A spirit-lamp is now 

 brought under the plate, and moved to and 

 fro till a number of small steam bubbles appear 

 upon the image. The spirit-lamp must be im- 

 mediately withdrawn. The remainder of the 

 chloride solution must be poured back into the 

 phial, to be used on another occasion. It is 

 lastly to be washed and examined. This operation has been repeated three or four 

 times with the happiest effect of giving fixity and force to the picture. It may then 

 be wiped with cotton without injury. The process of colouring these pictures is a 

 purely artificial one, which, while it destroys the beauty of the photograph, does not 

 in any way improve it as a picture. 



Daguerreotype Engraving. Several processes for etching the Daguerreotype plate 

 were introduced with more or less success. Professor Grove produced a few good 

 engravings by the action of voltaic electricity. Berard and Becquerel were also 

 enabled to produce some promising results by a similar process. The following 

 process by M. Claudet was carried out to some extent with every prospect of success : 

 A mixed acid, consisting of water, nitric acid, nitrate of potash, and common salt, 

 in certain proportions, being poured upon a Daguerreotype picture, attacks the pure 

 silver, forming a chloride of that metal, but does not affect the white parts, which are 

 produced by the mercury of the picture. This action does not last long. Water of 

 ammonia, containing a little chloride of silver in solution, dissolves the rest of that 

 chloride, which is then washed away, leaving the naked metal to be again attacked, 

 especially with the aid of heat. See COLLODION ; HELIOGRAPHY ; PHOTOGRAPHY. 



DAHIiUVZ:, the same as INULINE. The fecula obtained from elecampane and 

 from the dahlia, analogous in many respects to starch. It has not been employed in 

 the arts. 



DAXiARxriTE. Breithaupt's name for a Swedish variety of mispickel or arse- 

 nical pyrites. 



DAMAXl. See DAMMAR GUM. 

 DAIKASCEENXTTG. See DAMASKEENING. 



DAMASCUS BXiADES are swords or scimitars, presenting upon their surface 

 a variegated appearance si watering, as white, silvery, or black veins, in fine lin s. ..v 

 fillets ; fibrous, crossed, interlaced, or parallel, &c. They are brought from the East, 

 being fabricated chiefly at Damascus, whence their name. Their excellent quality 

 has become proverbial; for which reason these blades are much sought after l>y 

 military men, and are high priced. The oriental processes have never been satisfac- 

 torily described ; but of late years methods have been devised in Europe to imitate the 

 fabric very well. 



Clouet and Hachotte pointed out the three following processes for producing 

 Damascus blades : 1, that of parallel fillets; 2, that by torsion ; 3, the mosaic. The 

 first, which is still pursued by some French cutlers, consists in scooping out with a 

 graving tool the faces of a piece of stuff composed of thin plates of different kinds of 

 steel. These hollows are by a subsequent operation filled up, and brought to a level 

 with the external faces, upon which they subsequently form tress-like figures. 2. The 



