petre”, arrogate to themselves the discovery of a great truth.  Much more modest would it be and much more in the spirit of giving credit where credit is due to admit that, after long doubting the existence of such an entity, we have succeeded in confirming in fullness the truth of a great discovery which belongs to an unnamed genius of the past, or perhaps to a hundred of them who, working with life’s processes and familiar with them through long intimate association, saw in these invisible processes analogies that revealed to them the essential truth in such fullness as to enable them to build upon it an unfailing practice.

There is another practice followed by the Chinese, connected with the formation of nitrates in soils, which again emphasizes the national trait of saving and turning to use any and every thing worth while.  Our attention was called to this practice by Rev. A. E. Evans of Shunking, Szechwan province.  It rests upon the tendency of the earth floors of dwellings to become heavily charged with calcium nitrate through the natural processes of nitrification.  Calcium nitrate being deliquescent absorbs moisture sufficiently to dissolve and make the floor wet and sticky.  Dr. Evans’ attention was drawn to the wet floor in his own house, which be at first ascribed to insufficient ventilation, but which be was unable to remedy by improving that.  The father of one of his assistants, whose business consisted in purchasing the soil of such floors for producing potassium nitrate, used so much in China in the manufacture of fireworks and gunpowder, explained his difficulty and suggested the remedy.

This man goes from house to house through the village, purchasing the soil of floors which have thus become overcharged.  He procures a sample, tests it and announces what he will pay for the surface two, three or four inches, the price sometimes being as high as fifty cents for the privilege of removing the top layer of the floor, which the proprietors must replace.  He leaches the soil removed, to recover the calcium nitrate, and then pours the leachings through plant ashes containing potassium carbonate, for the purpose of transforming the calcium nitrate into the potassium nitrate or saltpeter.  Dr. Evans learned that during the four months preceding our interview this man had produced sufficient potassium nitrate to bring his sales up to $80, Mexican.  It was necessary for him to make a two-days journey to market his product.  In addition he paid a license fee of 80 cents per month.  He must purchase his fuel ashes and hire the services of two men.

When the nitrates which accumulate in the floors of dwellings are not collected for this purpose the soil goes to the fields to be used directly as a fertilizer, or it may be worked into compost.  In the course of time the earth used in the village walls and even in the construction of the houses may disintegrate so as to require removal, but in all such cases, as with the earth brick used in the kangs, the value of the soil has improved for composting and is generally so used.  This improvement of the soil will not appear strange when it is stated that such materials are usually from the subsoil, whose physical condition would improve when exposed to the weather, converting it in fact into an uncropped virgin soil.