74 ANNUAL OF SCIENTIFIC DISCOVERY. 



the last meeting of the American Association, and could not be dis- 

 tinguished from some metallic painting exhibited at the same time by 

 the Zinc White Company of New Jersey. The following is an an- 

 alysis of this shale, made by Dr. C. T. Jackson : 



Water, 8.5 ; silica, 51.3; alumina, 16.0; peroxide of iron, 20.0; 

 carbonate of lime, 2.8; magnesia with traces of manganese, 1.0. 

 Editors. 



TRANSPARENT CEMENT. 



AT the meeting of the Franklin Institute, on Sept. 19, an excellent 

 transparent substance, well adapted to replace Jeffries's marine glue, 

 for many purposes, particularly where a transparent joint is required, 

 as in the union of pieces of glass, invented by Mr. S. Lenher, was 

 exhibited, and its properties explained. Small glass boxes, for con- 

 taining microscopic objects, united by it, were shown. The compo- 

 sition of the cement is, caoutchouc fifteen grains, chloroform two 

 ounces, mastic half an ounce. The two first-named ingredients are 

 to be first mixed ; after the gum is dissolved, the mastic is added, and 

 the whole allowed to macerate for a week, which is about the time 

 required for the solution of the mastic in the cold. More of the caout- 

 chouc may be applied where great elasticity is desirable. The conven- 

 ience of its application with a brush, cold, recommends it for approval. 



METHOD OF HARDENING OBJECTS IN PLASTER OF PARIS. 



TAKE two parts of stearine, two parts of Venetian soap, one part of 

 pearlash, and twenty-four to thirty parts of a solution of caustic potash. 

 The stearine and the soap are cut into slices, mixed with the cold lye 

 and boiled for about half an hour, being constantly stirred. Whenever 

 the mass rises, a little cold lye is added. The pearlash, previously 

 moistened with a little rain-water, is then added, and the whole boiled 

 for a few minutes. The mass is then stirred until cold, when it is 

 mixed with so much cold lye that it becomes perfectly liquid, and 

 runs off the spoon without coagulating and contracting. Before using 

 this composition, it should be kept for several days well covered. It 

 may be preserved for years. Before applying it to the objects, they 

 should be well dusted, the stains scraped away, and then coated by 

 means of a thick brush with the wash , as long as the plaster of Paris 

 absorbs it, and left to dry. The coating is then dusted with leather 

 or a soft brush. If the surface has not become shining, the operation 

 must be repeated. Chemical Gazette. 



BRONZING PLASTER-CASTS. 



M. ELSNER states in the Comptes Renclus that a brownish-green 

 bronze for plaster figures may be very easily obtained by adding to a 

 solution in water of palm-oil soap, a mixture of sulphate of iron and 

 sulphate of copper in solution ; this furnishes a brownish-green pre- 

 cipitate, the color of which may be modified at pleasure by the addi- 



