L. TECHNOLOGY. 463 



amount of soluble phosphate of lime has been previously 

 added. The best proportion of the different ingredients is 

 said to consist of 700 parts of gypsum and 300 of. slag, to 

 which, for use in the open air, 28 parts of soluble phosphate 

 of lime are to be added. This, however, may be replaced by 

 a corresponding quantity, 6 to 14 parts, of phosphoric or bo- 

 racic acid, or any other substance capable of combination 

 with the iron. The superphosphate of lime may also be 

 substituted for the soluble phosphate. For this, however, an 

 equal quantity of slag must be used. On the other hand, if 

 the quantity of soluble phosphate of lime is increased, the 

 sulphate may be entirely omitted. 



It is alway necessary to have the different ingredients fine- 

 ly pulverized and w^ell mixed. When used, a sufficient quan- 

 tity of water is to be added, and the whole thoroughly stirred 

 together.. With these substances blocks can be made as 

 hard as marble, and capable of imitating this substance very 

 closely. For this purpose the necessary moulds are to be 

 laid upon a porous bed gypsum, for instance and subject- 

 ed, by means of a screw or hydraulic press, to a great press- 

 ure. The cement, thus compressed, is removed from the mould 

 in the form of a very hard block, which takes as fine a polish 

 as marble, and may be stained or colored previous to the 

 pressure in such a way as closely to resemble the different 

 colors of this rock. This artificial marble resists the influ- 

 ence of air, moisture, and frost, and is said to be well adapted 

 for the fronts of houses, floor-tiles, etc. 12 (7,xl., 318. 



COMPOSITION FOR SHIPS' BOTTOMS. 



A composition for coating ships and boats has been de- 

 vised, which consists of paraffine mixed with metallic parti- 

 cles, or with a poisonous substance, such as arsenic, sulphate 

 of copper, etc., or else combined with creosote dissolved in 

 heavy oils. This is to be applied hot to the bottom of the 

 vessel, and renewed from time to time as occasion requires. 

 17 (7,334, July. 



EBONY FROM SEA-WEED. 



It may interest some of our readers who reside near- the 

 sea-coast to learn that there is considerable commercial value 

 in the common sea-weeds which are thrown up so abundant- 



