CHEMICAL SCIENCE. 273 



rocks. The manner in wliich he made his examination was by taking certain 

 portions of eleven different species of rock, having the soil which covered it 

 entirely removed. The rock was then bruised till it had the appearance of 

 common soil. He had introduced above 22 cwt. into his garden, and raised 

 a crop of autumn grain upon it, and he was thus able to advance a general 

 theory with regard to the presence of phosphoric acid in the rock. Mr. Gilbert 

 said that the rock would be of little use for manufacturing and agricultural 

 purposes unless it contained at least 50 per cent, of phosphate of lime. 



ASSIMILATION OF NITROGEN BY PLANTS. 



This subject is still under discussion among the French savans. M. Bous- 

 singault persists in denying, more strongly than ever, that plants can assim- 

 ilate nitrogen directly from the atmosphere. His experiments have always 

 been made on limited portions of air, while M. Yille, on his side, has constantly 

 operated in the free air, and perseveringly sustains the fixation of nitrogen. 

 The following explanation, offered by M. Eoy, appears to harmonize these 

 discordant results. He admits that nitrogen from the air is not absorbed by 

 the leaves, but that, when dissolved in water, it is taken up by the roots. 

 But a plant in an inclosed portion of atmosphere, which is developed wholly in 

 this condition, does not transpire water by the leaves ; and hence must absorb 

 by the roots only a veiy limited quantity of water, and consequently an inap- 

 preciable quantity of nitrogen. Such is the case in the experments of Bous- 

 singault. On the contrary, a plant endowed with great powers of transpira- 

 tion, as wheat, placed in the apparatus of M. Ville, absorbs as much more 

 water as the transpiration is more active from the renewal of the air. The 

 quantity of nitrogen which is then taken up by the water into the interior 

 of the plant, and assimilated, is sufficient to be sensible in analysis. Paris 

 Correspondence of Siltima/i's Journal. 



ON THE PRODUCTION OF CARBONIC ACID GAS BY THE SOIL, 



ORGANIC, AND MANURES. 



Since the time of Saussure we have known that humid organic matters, 

 when exposed to the air, remove oxygen, absorb a portion, and that there is 

 a production of water with their hydrogen, and carbonic acid at the expense 

 of their carbon. But hitherto no chemist has tried to appreciate, even ap- 

 proximatively, the quantity of carbonic acid which the soil and substances in 

 the course of decomposition emit spontaneously into the air. M. Corenwin- 

 der, in a recent communication to the French Academy, states that he has 

 ascertained that argilaceous earth, enriched with farm-yard manure, exhales, 

 in 24 hours, 15'70 litres per square metre of surface. This earth contained 12 

 to 13 per cent, of moisture, and the thickness of the layer experimented on 

 was 8 centimetres. The temperature varied from 68 to 86 Fahrenheit 

 during these observations. As might be expected a soil which contains but 

 little manure produces a smaller quantity of carbonic acid. By stirring the 

 surface a larger proportion of carbonic acid is disengaged, because fresh rnole- 



