Reviews. — Liebig''8 Organic Chemistry. 849 



power of condensing gases within its pores, and particularly carbonic 

 acid. And it is by virtue of this power that the roots of plants are 

 suppb'ed in charcoal exactly as in humus, with an atmosphere of car- 

 bonic acid and air, which is renewed as quickly as it is abstracted. 



In charcoal powder, which had been used for this purpose by Lu- 

 kas for several years, Buchner found a brown substance soluble in 

 alkalies. This substance was evidently due to the secretions from 

 the roots of the plants which grew in it. 



A plant placed in a closed vessel in which the air, and therefore 

 the carbonic acid, cannot be renewed, dies exactly as it would do in 

 the vacuum of an air-pump, or in an atmosphere of nitrogen or car- 

 bonic acid, even though its roots be fixed in the richest mould. 



In con6rmation of this, the American editor appends the 

 following, from his own experience: — 



A few years since I had an opportunity of observing a striking in- 

 stance of the eflfect of carbonic acid upon vegetation in the volcanic 

 island of St. Michael (Azores.) The gas issued from a fissure in the 

 base of a hill of trachyte and tuffa from which a level field of some 

 acres extended. This field, at the time of my visit, was in part cov- 

 ered with Indian corn. The corn at the distance of ten or fifteen 

 yards from the fissure, was nearly full grown, and of the usual height, 

 but the height regularly diminished until within five or six feet of the 

 hill, where it attained but a few inches. This effect was owing to 

 the great specific gravity of the carbonic acid, and its spreading upon 

 the ground, but as the distance increased, and it became more and 

 more mingled with atmospheric air, it had produced less and less 

 eflfect. 



The fertilizing properties of the atmosphere, and especially 

 of rain, are thus ingeniously proved, from the presence of 

 ammonia, a well known stimulant in vegetation, and the pro- 

 duct of fermenting animal manures, which modern farmers 

 have learned to be too precious to waste its odors from care- 

 lessly constructed barns. 



If a pound of rain water contain only one fourth of a grain of am- 

 monia, then a field of forty thousand square feet must receive annu- 

 ally upwards of eighty pounds of ammonia, or sixty-five pounds of 

 nitrogen ; for, by the observations of Schubler, which were for- 

 merly alluded to, about seven hundred thousand pounds of rain fall 

 over this surface in four months, and consequently the annual fall 

 must be two million five hundred thousand pounds. This is much 

 more nitrogen than is contained in the form of vegetable albumen 

 and gluten, in two thousand six hundred and fifty pounds of wood, 

 two thousand eight hundred pounds of hay, or two hundred cwt. of 

 beet root, which are the yearly produce of such a field, but it is less 

 than the straw, roots, and grain of corn which might grow on the 

 same surface, would contain. 



Experiments, made in this laboratory (Giessen^ with the greatest 

 care and exactness, have placed the presence of ammonia in ruin- 



