“A serious accident occurred in 1818, on board a vessel named the Arthur, which sailed from Rouen with a cargo of poudrette for Guadaloupe. During the voyage a disease broke out on board which carried off half the crew, and left the remainder in a deplorable state of health when they reached their destination. It attacked also the men who landed the cargo; they all suffered in a greater or less degree. The poudrette was proved to have been shipped during a wet season, and to have been exposed before and during shipment, in a manner to allow it to absorb a considerable quantity of moisture. The accident appears to have been due to the subsequent fermentation of the mass in the hold—increased to an intense degree by the moisture it had acquired, and by the heat of a tropical climate.
“M. Parent du Châtelet, to whom the matter was referred, recommended that to guard against similar accidents in future, the poudrette intended for exportation, in order to deprive it entirely of humidity, should be mixed with an absorbent powder, such as quicklime, and that it should be packed in casks to protect it from moisture during the voyage.”
[75] “It is in the upper basins,” adds the Reports, “that the first separation of the liquids and solids takes place, the latter falling to the bottom, and the former gradually flowing off through a sluice into the lower basins. This first separation, however, is by no means complete, a considerable deposit taking place in the lower basins. The mass in the upper basins, after three or four years, then appears like a thick mud, half liquid, half solid; it is of depth varying from 12 to 15 feet. In order entirely to get rid of the liquids, deep channels are then cut across the mass, by which they are drained off, when the deposit soon becomes sufficiently stiff to permit of its being dug out and spread upon the drying-ground, where, to assist the desiccation, it is turned over two or three times a-day by means of a harrow drawn by a horse.
“The time necessary for the requisite desiccation varies a good deal, according to the season of the year, the temperature, and the dry or moist state of the atmosphere. Ere yet it is entirely deprived of humidity, the matter is collected into heaps, varying in size usually from 8 to 10 yards high, and from 60 to 80 yards long, by 25 or 30 yards wide. These heaps or mounds generally remain a twelvemonth untouched, sometimes even for two or three years; but as fast as the material is required, they are worked from one of the sides by means of pickaxes, shovels, and rakes; the pieces separated are then easily broken and reduced to powder, foreign substances being carefully excluded. This operation, which is the last the matter undergoes, is performed by women. The poudrette then appears like a mould of a grey-black colour, light, greasy to the touch, finely grained, and giving out a particular faint and nauseous odour.
“The finer particles of matter carried by the liquids into the lower basins, and there more gradually deposited in combination with a precipitate from the urine, yield a variety of poudrette, preferred, by the farmers, for its superior fertilizing properties. In this case the drying process is conducted more slowly and with more difficulty than in the other, but more completely.
“In general the poudrette is dried with great difficulty; it appears to have an extreme affinity for water; few substances give out moisture more slowly, or absorb it more greedily from the air.
“A good deal of heat is generated in the heaps of desiccated matter. This is always sensible to the touch, and sometimes results in spontaneous combustion.
“The intensity of this heat is not in proportion to the elevation of temperature of the atmosphere. It is promoted by moisture. The only means of extinguishing the fire when it is once developed is to turn over the mass from top to bottom, in order to expose it to the air. Water thrown upon it, unless in very large quantities, would only increase its activity.”
[76] 4¼ heaped bushels each, English measure.
[77] I did not hear any of the London nightmen or sewermen complain of inflammation in the eyes, and no such effect was visible; nor that they suffered from temporary blindness, or were, indeed, thrown out of work from any such cause; they merely remarked that they were first dazzled, or “dazed,” with the soil. But the labour of the Parisian is far more continuous and regular than the London nightman, owing in a great degree to the system of movable cesspools in Paris.