S02 Scientific Intelligence. — Arts. 



18. MetJiod of cleansing Wool from its Grease^ and econo- 

 mis'ing the residue. — M. Darcet, who has long been consulted 

 by manufacturers, advised the following method, which was 

 tried with complete success. Immerse the wool, well washed 

 from dirt, in a vessel containing spirits of turpentine, and let it 

 remain from thirty -six to forty-eight hours. Withdraw, and 

 immerse a fresh quantity. By means of a press, force out all 

 the adhering spirit, spread the wool out to dry, and, when it is 

 to be used, wash it in warm water containing a little alkali. 

 When the spirits of turpentine will no longer act upon or re- 

 move the grease, distil it for fresh use, and the matter remain- 

 ing in the still, treated with soda, will make good soap. 



19. Stucco for Walls, — In Italy great use is made of a stucco 

 which gives to the walls the brilliancy, the cleanliness, and al- 

 most the hardness, of marble. It may be variously coloured, 

 to suit the taste of the employer.. This stucco is made very 

 easily, by mixing lime and pulverized marble, in nearly equal 

 proportions, according to the meagerness or richness of the mar- 

 ble. A paste or mortar is made of this mixture, and applied to 

 the wall in the thickness of a five-franc piece, with a trowel wet 

 with soap-suds, and in such a way, that the whole of the wall 

 may be finished in the same day. None but mineral colours 

 should be mixed with the stucco, as the lime would destroy 

 those derived from the vegetable kingdom. To obtain the 

 greatest brilliancy, the mortar should be applied with a cold 

 trowel. Workmen, for the sake of ease and expedition, usually 

 employ it warm. Chips and fragments of marble may be ad- 

 vantageously employed for this purpose. In cases where the 

 appearance of a marbled wall would be objectionable, on account 

 of its coldness, any portion of it may be covered with paper. 



20. Preservation of Substances by means of Alkalies, — M. 

 Payen has preserved, during many months, polished instruments 

 of iron and steel, by keeping them in solutions of potash or so- 

 lutions of potash or soda — saturated solutions, diluted with one, 

 two, or three, times their weight of water. He at first thought 

 that the preserving power depended upon the disappearance of 

 the air and carbonic acid in the alkaline mixture, but he after- 

 wards concluded that alkalinity acted an essential part in the 

 phenomenon. In fact, a very small quantity of alkali is suffi- 



