THE FARMER'S MAGAZINE. 



321 



From the 5tli August to the 17th September, ia 43 

 days the production of nitre made rapid progress. The 

 quantity of saltpetre rose from 12.05 grammes, when the 

 little nitre-bed was established, to 280.03 grammes. 

 From the 17th September to the 2nd October, the nitri- 

 fication remained stationary. 



At first sight the equivalent of 200 grammes of nitrate 

 of potash diiTused in a cubic metre of earth will appear 

 a very feeble dose of azotous manure. But, in reality, 

 the earth is only the excipient of the fertilizing principles; 

 it is therefore in the water by which it is penetrated that, 

 most generally at least, reside the agents destined to in- 

 terpose in culture. Now, 100 parts of the soil of Lieb- 

 frauenberg absorb, when completely saturated and with- 

 out changing its volume, 12 parts of water, say 546 

 kilogrammes per cubic metre. Every litre of water 

 absorbed will contain therefore the equivalent of 0.512 

 grammes of nitrate of potash. Arable land is still suffi- 

 ciently moistened when it retains no more than half the 

 wateritiscapableof absorbing : being then more accessible 

 to the air, it becomes more favourable to vegetation. In 

 that state every litre of water will contain 1.024 grammes 

 of nitrate, representing 0.172 grammes of ammonia, 

 0.141 grammes of assimilable azote, the germ of about 

 1 gramme of the proteous matter, the dry vegetable meat 

 that the plant is capable of organizing. 



I have already said that the compost owes not its 

 fertilizing properties to saltpetre alone. I have thought 

 that in order to complete the investigation it would be 

 proper to seek for the azote and the carbon, the phos- 

 phoric acid and the ammonia, as I had already done 

 with the vegetable earth, for these are the actual or 

 approximate elements of fecundity. 



The compost of the mai-ket-gardeners of Paris, which 

 I have more closely examined, is the result of the slow 

 decomposition of dung operated in the beds, established 

 to determine that vegetation as precarious as vigorous, 

 which is the true type of the most intense culture that it 

 is possible for man to practice. 



In order to form a hot-bed, we cover the soil with a 

 dressing of horse-dung, of 1 m. 40 wide, and m. 30 

 thick : we then water and press it strongly. Upon this 

 basis we depose the bed of earth from 0.15 to 0.18 

 deep, more or less, completed by previous preparation, 

 in which the plants develope themselves. 



When we take away the hot-bed, the dung that con- 

 stitutes the base is converted into an incomplete compost. 

 This is a new earth, very porous, which we leave to 

 acquire age by laying in heaps. There it subsides, be- 

 comes more dense, more homogeneous, more earthy ; it 

 is in this state that we form of it the upper stratum, the 

 cultivable soil of a new hot-bed. 



The compost obtained in one year not being employed 

 entirely in the formation of the hot-beds of the succeed- 

 ing year, there always remains an excess that the mar- 

 ket-gardeners sell for top-dressing the lawns of pleasure- 

 grounds. 



I have examined two specimens of compost, one hav- 

 ing been exposed on a heap for four or five months 

 belonging to a market gardener ; the other a new com- 

 post taken from a hot-bed of a garden belonging to M. 



Vilmorin. The first was dosed with dry matter the 

 equivalent of 1.071 grams, of nitrate of potash per kilo- 

 gramme ; in the second, the equivalent of 0.940 grams, 

 of the same salt. With the magnifying-glass we per- 

 ceived in these composts fragments of quartz, very 

 limpid and colourless, small calcareous nodules, detritus 

 of vegetables more or less marred, having a brown tint 

 acquired from the peat. The compost has otherwise 

 much analogy with vegetable earth, as it is easy to satisfy 

 ourselves by comparing its composition with those of 

 different earths. 



1st. The mould of a kitchen-garden at Bischwiller, 

 near Haguenan : soil sandy, strongly manured. 



2nd. The light mould of the kitchen-garden of Lieb- 

 frauenberg. 



3rd. A very argillaceous earth, very strong, from 

 Bechelbronn, taken in autumn in a soil where wheat had 

 been harvested. 



IN A KILOGRAMME OF MATTER DRIED IN THE AIR: 



We find, in fact, that the compost and vegetable 

 mould taken in situations sufficiently various, present, 

 notwithstanding, in their constitution, the same active 

 principles, and that the real diffierence lies only 

 in their properties. Thus it appears that a fertile earth 

 may be represented by compost disseminated with a 

 quantity, more or less strong, of a mineral basis, whether 

 argillaceous, calcareous, or siliceous. If, for example, 

 we add 4 kilogrammes of sand taken from the sand- 

 stone of the Vosges to 1 kilogramme of the market- 

 gardeners' compost near Paris, we shall obtain a mixture 

 approaching in its aspect and composition the vegetable 

 mould of Liebfrauenberg, and differing from it certainly 

 less than the latter differs from the mould of Bische- 

 viller, of which, however, the sandy basis possesses the 

 same nature and origin. 



In one kilogramme there was of 



Grammes. 

 Azote entering into the composition of 



organic matters 2.101 



Ammonia perfectly formed 0.024 



Nitrate, expressed by nitrate of potash. ... 0.212 



Phosphoric acid 2.560 



Lime 12600 



Carbon belonging to organic substances . . 19.800 



A happy circumstance has furnished me with an 

 opportunity of extending my investigations to vegetable 

 earths, which M. Le Gendre Declay, a zealous traveller, 

 had reported on the shores of the Amazons, and its 



