268 ANNUAL OF SCIENTIFIC DISCOVERY. 



cotton are added in succession, until the mass has attained the consistency 

 of dough. This mass is preserved in large pieces resembling loaves of 

 bread. If it is to be used, it is stirred up with linseed oil until it becomes 

 fluid, and fit to make a coating, which is painted over twice or thrice. 

 Cements so prepared and allowed to dry, acquire the hardness of stone, resist 

 all moisture, and possess an indestructible durability. 



ACTION OF SEA-WATER ON CEilENTS. 



M. Vicat states in a communication to the French Academy, that he has 

 determined as the result of his experiments, that sea-water will destroy every 

 cement, mortar, or puozzolana, if it can penetrate into the mass immersed in 

 it. As, however, certain of these compounds are perfectly durable when con- 

 stantly immersed in sea-water, they can not have been penetrated by it. Its 

 penetration has been prevented by the surfaces, and the power of this ina- 

 bility to penetrate is chiefly caused by a superficial coating of carbonate of 

 lime which has formed either anteriorly or posteriorly to their immersion, 

 and which in tune augments in thickness. The effect of a kind of cementa- 

 tion produced by the decomposition of the sulphate of magnesia, of the sea- 

 water and the deposition of carbonate of magnesia, in the superficial tissue 

 of the mass, and the formation of incrustations and submarine vegetation, 

 contributes also to this impermeability. But all such superficial impermeable 

 coatings are not attached with the same force to the mass which they en- 

 velop. The differences which have been observed in this respect depend in 

 some cases upon the chemical constitution and upon the peculiar cohesion of 

 the silicates, and in others upon their submarine situation, relative to the ac- 

 tion upon the waves and the rolling and dashing of shingle upon them. 

 Hence the differences which have been observed by engineers in the durability 

 of concretes of which such silicates form the gange. Comptes Eendus, Jan. 

 1854. 



ON THE PRODUCTION OF ALCOHOL FROM BICARBTJRETED 



HYDROGEN. 



The following account of this most important chemical discovery of the 

 year is taken from the proceedings of the French Academy : 



When the chemist exerts his skill on materials of organic origin, he ex- 

 tracts a series of substances, each proceeding from the other, whose composi- 

 tion becomes more and more simple, until it reaches some species known to 

 mineral chemistry. Vegetable economy constantly realizes under our eyes the 

 inverse operation ; it takes in air, water, and mineral elements which it assimi- 

 lates, and, in virtue of certain of its own forces, disposes them in molecular 

 groups of a certain stability. It would appear as probable that these forces 

 are inherent to the exercise of life ; nevertheless it may be conceived that be- 

 fore the constant challenge given by the "subtlety of nature" to the "sub- 

 tlety of sense and intellect," science should endeavor to imitate nature, and 

 try to ascend in the series of combinations from the simplest to the composite. 



