250 ANNUAL OF SCIENTIFIC DISCOVERY. 



used for watering the cress had lost 2,367 grammes of ulmic acid, as 

 it was given by the ulmate of lime dried in vacuo. It might be sup- 

 posed that the ulmic acid might have remained in the soil, under an 

 unknown form, which might escape the action of re-agents ; but this 

 transformation could not be the result of the contact of the ulmic 

 acid either with the earthy matter, or with the external parts of the 

 roots. Now, this is a question of proving that this acid is absorbed, 

 and not of saying what becomes of it after the absorption. 



This experiment and those of M. Soubeiran, seem to me to prove 

 the absorption of the soluble ulmates during vegetation, and at the 

 same time their utility. Comptes Rendu-s, 1852. 



RAIN, A SOURCE OF THE NITROGEN IN VEGETATION. 



M. BARRAL, from some analyses of rain-water collected at two 

 distinct spots in the grounds of the Observatory at Paris, during the 

 last five and six months of the past year, has shown us that the rain- 

 water is there charged with nitric acid, ammonia, chlorine, lime and 

 magnesia, to an extent scarcely to be credited, were it not the actual 

 result of experiment. Taking the average of these analyses, and 

 reducing the French weights to our own standard of 7.000 grains to 

 the pound, it will be seen, in these six months, the rain which fell on a 

 space of ground at the Observatory at Paris, equal in area to an 

 English acre, contained, as nearly as possible, 7.75 pounds of ammonia; 

 36.50 pounds of nitric acid ; 5.56 pounds of chlorine ; 12.60 pounds of 

 lime ; 4.81 pounds of magnesia. 



From July to December is usually the drier half of the year, as well 

 as that in which the less fuel is consumed, so that we may safely double 

 these quantities, in estimating the annual supply per acre of nitrogene- 

 ous compounds, gradually distributed over the country by the rain. 

 For the sake of illustration, we have calculated the amount of the 

 solid constituents of the rain falling on an area eqvial in extent to 

 Great Britain, and balancing the various causes likely to lessen or 

 to increase the quantity of these matters, which would so fall on this 

 island, we may venture to set one against the other, and apply the 

 above statement to our own country, as the basis of an estimate, Avhich 

 singularly manifests the "power of littles," as well as the grand 

 scale on which even the minutest of natural phenomena proceed. 

 Thus, on the Parisian data, the weights of these fertilizing materials 

 annually supplied to the soil of this island by the rain, amount to 

 about 400,000 tons of ammonia ; 1,850,000 tons of nitric acid ; 279,- 

 000 tons of chlorine ; 640,000 tons of lime ; 244,000 tons of magnesia. 



Making every allowance for errors of experiment, which, however, 

 would rather increase than diminish these quantities, excepting, it may 

 be, the amounts of the two last on the list, these researches of M. 

 Barrel prove to us that, the amount of fertilizing matter conveyed to 

 the soil by the rain, must exercise a constant and most important 

 influence on the vegetation of a country. These facts also tend to 

 throw still further doubt upon the peculiar efficiency of the salts of 



