Page:Popular Science Monthly Volume 18.djvu/832

812 tanks, occupying six hectares, or fifteen acres, would Lave to be built up with walls of solid masonry, at an expense of about 1,200,000 francs. A similar sum may be added for the installation of the roads, ways, carts, and other accessories, making a total of about 2,500,000 francs, or $500,000—a mere drop in the budget of the city of Paris, The expense of labor at Essonnes is twenty francs a day; at thirty times as much, it would be 600 francs, or $120, a day at Paris. Add to this the expense of carrying away the manure, in case no return is derived from sales, and the price of the daily supply of lime, estimated at the highest probable figures, and the whole daily expense of operation at Paris rises to 3,000 francs, or $600. The year's aggregate of these daily expenses, with the interest on the cost of original establishment (which we now place, to cover all possible additions, at double the amount of the estimate we have just made), gives the total cost of the application of the Essonnes system to the purification of the sewer waters of Paris at 1,345,000 francs, or about $260,000, a year. The cost of managing the proposed works for the absorption of the sewage in the forest of St. Germain is estimated at 2,120,000 francs, or about $403,000, a year, showing a difference of more than $140,000 a year in favor of the plan of desiccation as pursued at Essonnes.

The difference in favor of this plan is much greater than appears from these figures, for no account has been taken of the probable economic value of the desiccated mud as manure. By actual analysis this mud has been found to contain from eleven to fifteen grammes of nitrogenous substances, and from twenty to twenty-five grammes of phosphate of lime, per cubic metre. The whole deposit from a year's sewage of Paris would contain nitrogenous matters enough to suffice for the fertilization of 75,000 acres of land. It is certain that a sale would be gradually found for this valuable matter, the proceeds of which, estimated eventually to amount possibly to 1,500,000 francs a year, would in the end more than defray the entire cost of maintaining the system of extraction.

 

VENTS, in the present time, follow one another with such rapidity, and the favorites of society pass in such constant succession over the stage, that the most startling occurrences are only regarded as nine days' wonders; and men who have even filled a prominent place are almost forgotten before a monument is erected to their memory. Under such circumstances it may prove an almost hopeless task to recall attention to the character of a man who held only a 