576 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



they are developed in warm water, and fine, vigorous copies 

 are the result. 12 A, May 22, 1873, 67. 



szekely's bkilliant photographs. 



In order to avoid the usual streno'theninsj of the neg^ative, 

 and any consequent necessity for retouching, the requisite in- 

 tensity is obtained by accurately superposing two simply de- 

 veloped negatives, after having varnished them, and fasten- 

 ing them in position by means of paper strij^s pasted on the 

 edges. The combination is printed from in difi'used daylight 

 as an ordinary negative, and the pictures are said to have a 

 strength and softness unattainable by a single negative. 15 

 C, 1873,VL, 86. 



COATING FOR PLASTER CASTS,, ETC. 



Articles of glass and pkister are frequently covered of late 

 with mica powder, instead of bronze, and the following proc- 

 ess is recommended by Schelhass, of Munich, as affording a 

 cheap, durable, and beautiful coating for such articles, supe- 

 rior to metallic bronze in being unafiected by sulphurous va- 

 pors, and capable of being freed from dust and dirt, without 

 injury, by washing. Mica scales, perfectly whitened by boil- 

 ing with hydrochloric acid, or by calcination, are washed and 

 dried, and finely pulverized by grinding, sifting, and elutria- 

 tion, then stirred into thinned collodion, and laid on, a num- 

 ber of times, like a color, with a soft brush. 6 C, Hay 15, 

 1873,199. 



RENDERING FABRICS TVATER-PROOF. 



Dissolve one part by weight of caoutchouc, and one of par- 

 affiue or stearine, in two of benzine; dilute as much as neces- 

 sary, and either saturate the fabric with it, or lay it on with 

 a brush. 14 (7, CCVIIL, 1873, 159. 



IMPROVED CARDING-MACHINE. 



An important improvement in carding-machines has re- 

 cently been made in England by the substitution of flat for 

 round wires. The former have greater resistance, when w^ork- 

 ed edgewise, and are consequently less liable to break or be- 

 come impaired ; and, since they require less and lighter grind- 

 ing, they also last longer. Their points being shai-per and 



