THE FARMER'S MAGAZINE. 



543 



compounds existing or forming in the atmosphere. I 

 have succeeded in detecting their presence in the atmo- 

 sphere by the means I will now describe : 



APPARATUS TO DETERMINE THE APPEARANCE OF 

 NITRATES. 



Six tubes in the shape of an U were placed, one 

 after the other, in connection with an aspirator. The 

 two first tubes, through which the inhaled air 

 passed first, were filled with small fragments of brick, 

 impregnated with a solution of carbonate of potash*. 

 Afterwards came two tubes filled with alkaline pumice 

 stones; then, last of all, two other tubes, which con- 

 tained chalk soaked with a solution of carbonate of 

 potash. The apparatus was sheltered from the rain in 

 a box, in which air was let in at three inches above the 

 turf, close to a vine. 



The aspirater worked almost without any interrup- 

 tion night and day from the 7th of July to the 7th of 

 October, 1856. The matter contained in the tubes 

 was kept in a constant state of humidity. The experi- 

 ment being finished, a very appreciable quantity of 

 nitrate was found in the first tube. There was still a 

 trace of that salt in the second tube, and not at all in 

 the others ; at all events, not the least trace was per- 

 ceived, although, on the one hand, the tincture of indigo, 

 and on the other the gold leaf, are capable of detecting 

 clearly 0:00275 of a grain of nitric acid. 



The aspired air came directly into the first tube, in 

 which fragments of bricks, imbibed with a solution of 

 carbonate of potasli, were placed. I did not think it 

 necessary to make it pass through sulphuric pumice 

 stone to retain the ammoniacal vapour. What I wanted 

 to detect was simply tl)e presence or the absence of 

 nitrate in an earthy substance, porous in its nature, 

 imbibed with dissolved carbonate of potash, and sub- 

 mitted to a current of air. Whatever the cause may 

 have been, there undoubtedly was an appearance of 

 nitrate. I say appearance, and not production, because 

 the experiment, such as it had been conducted, did not 

 demonstrate anything else. In effect, if it be possible 

 that the ammonia of the air which was not removed had 

 been nitrified by the contact of the potash, mixed with 

 the porous body by some ozoned oxygen, it is not un- 

 likely, on the other hand, that some nitrates may have 

 been brought with the dust, which the atmosphere always 

 holds in suspension. Saltpetre is everywhere on the 

 surface of the globe ; the most minute particles of the 

 vegetable earth which the wind carries about are evi- 

 dently provided with it, and the air brought into the 

 apparatus may have deposited some upon the damp 

 bricks of the first tubes. I must observe here, that if 

 even air had been at first directed upon sulphuric 

 pumice stones, in order to fix the ammonia, this means 

 would not have prevented the nitrates from intervening, 

 for, insomuch as they are concerned, the action of the 

 sulphuric acid would have been confined to keeping 

 their basis ; and the nitric acid, freed or transformed 

 into nitrous compounds, would have been carried away 

 by the current, and retained by the potash of the first 

 tubes. 



However that may be, and in considering solely the fact 

 of the appearance of nitre where there was none before 

 the passage of air, it will be acknowledged that this ex- 



* The fragments came from a new brick, but which had 

 been deposited for a long time in a warehouse. They had 

 been washed with distilled water, before they were calcined, 

 in order to take away the nitrates which they might have 

 contained, and which, calciaation without charcoal does not 

 always completely destroy, or rather transforms into nitrate 

 or other very persisting nitrous compouuda. The carbonate 

 of potash had been prepared by reducing to ashes pure cream 

 of tartar ; and care had been taken to ascertain thut it did 

 not contain the slightest trace of nitrate. 



periment, made above a turf near a vine, and upon the 

 border of an immense forest, leads to a result quite con- 

 formable to that obtained long before by M. de Luca, 

 in similar circumstances as regards the abundance of 

 vegetation, since that eminent observer has found that 

 there is a formation of nitric acid when air deprived 

 of ammonia, free from dust, and taken from a green- 

 house where many plants of all kinds are grown, is 

 passed through a solution of potash. 



DETERMINATION OF THE NITROGEN AFFORDED BY 

 THE ATMOSPHERE. 



A cylindric vase, made of crystal, one inch and a-half 

 deep, and presenting a surface equal to that of flower pots, 

 was placed near the plants under experiment. Half-a- 

 pound of washed and calcined sand, to which had been 

 mixed 155 grains of oxalic acid, considered as pure, but 

 containing in reality 0,001705 grain of nitrogen, which 

 was accounted for, was placed into it. The mixture, 

 kept damp, remained exposed to the atmosphere. 

 When it rained, and during the night, to avoid the 

 dew, the vase was covered with a glass bell. After 

 seven weeks the sand had absorbed 0,003015 grain 

 of nitrogen, a part of which certainly formed some 

 ammonia. This is, however, a mere information, 

 for everything leads to the presumption that the 

 quantity of nitrous principles which a damp soil 

 receives from the atmosphere, depends at the same 

 time upon the surface exposed, and the length of time 

 of the exposure, and also upon the locality. Upon the 

 locality : this is a circumstance which must not be over- 

 looked, for air is not always equally pure. The im- 

 purity of rain-water demonstrates, perhaps, better than 

 the most delicate analysis could do, the degree of im- 

 purity of the atmosphere. It is thus that the rain- 

 water collected at Paris and Lyons contain much more 

 ammonia, nitrates, and organic matters, than the rain, 

 snow, fog, and dew which fall at a great distance from 

 centres of population.* 



INFLUENCE OF THE SOLUBLE NITROGEN UPON THE 

 DEVELOPMENT OF VEGETABLE ORGANISM. 



The preceding experiments have established that the 

 phosphate of lime and the alkaline salts added to the 

 soil, without the concurrence of a nitrous manure, 

 do not sensibly contribute to the development of 

 organism. The matter formed in that condition by the 

 plant does not weigh much more than that which is 

 produced when the ground, rendered barren by fire, 

 contains no saline substance ; when, for instance, vege- 

 tation is accomplished with the only resources which are 

 found in the seed, and ends only in a limit plant. 

 When, on the contrary, phosphate and saltpetre are 

 united, they act with theenergy of farm -yard manure. I 

 believe it is permitted to conclude from those facts, 

 that the growth of a plant is subordinate to the previous 

 absorption of a soluble nitrogenous substance, the 

 effects of which it is not perhaps impossible to cal- 

 culate : it is at least what I have attempted. 



To that end divers preparations of nitrate of soda 

 were introduced into calcined sand provided with phos- 

 phate of lime and salts of potash. 



The soil, calcined and improved with phosphate, 

 was divided and put into four flower vases, free from 

 every organic matter. 



Two seeds of Helianthus argophyllus, weighing 

 1.7050 grains, were placed into each of the vases. 



The vegetation lasted fifty days. 



The water of irrigation, free from ammonia, had 



* From observations made by M. Batral, at Paris, and M. 

 Birreau, at Lyons; compared with those I have obtained at 

 Liebfuruenberg, and those of Messrs. Lawes and Gilbert, re- 

 gistered at Rothamstead. 



