M. TECHNOLOGY. 497 



if desired, are painted, reversed, upon it with black japan. 

 If the layer of gold is too thin the varnish may be visible 

 throuo-h it, and mar the eftect. When the varnish is thor- 

 oughly dry, the excess of gilding is softened with water, and 

 washed off", while the designs protected by it remain, and ex- 

 hibit a very fine lustre, if the manipulation has been careful. 

 Usually the whole glass is then blacked up with a dark oil- 

 color, which renders the letters more distinct, protects them, 

 and reduces the disturbing effect of reflection. 14 (7, CCXVI., 

 184. 



PURIFICATION OF FIXED VEGETABLE OILS. 



Fixed vegetable oils are purified much more perfectly and 

 cheaply than usual by a process practiced in England, in 

 which the agitation of the oil, during purification, is accom- 

 plished by a current of air forced into it through a system 

 of perforated tubes entering the bottom of the vessel, instead 

 of by means of revolving paddles. The sulphuric acid is 

 added to the oil, as usual, cautiously during the agitation, 

 and on account of its more thorough contact with the oil 

 effected by this method, the carbonization of the albuminous 

 and other impurities is more complete. The acid is removed 

 from the purified oil, as usual, and any residue of water by 

 means of steam heat. 5 6', XL., 396. 



OIL-PAINT FOR FLOORS. 



None but earth-colors should be used in painting floors, 

 and the rapid wearing off of a coating of oil-paint on a floor 

 is a sure indication that white-lead has been mixed with the 

 paint. This is generally the case, since it causes the paint 

 to cover better and spread easier. Even the employment of 

 a varnish that has been boiled with litharge should be avoid- 

 ed, and one boiled with borate of manganese preferred. It 

 is also very important that the first coating should be per 

 fectly dry before a second is laid on. 5 C, XL., 23. 



PALMIERl's DRAGOMETER. 



Professor Palmieri has constructed an instrument which 

 he calls a " dragometer." It is intended to determine tho 

 character of oils and textures by means of electricity. Among 

 the properties claimed for it are : 1. It will show the quality 



