people themselves, under the supervision of the committee; about nine tenths of the pieces were well taken. care of. The committee estimate that the potato crop averaged about fifteen bushels per lot, giving fourteen thousand one hundred and seventy-five bushels in all; and large quantities of beans, turnips, and other vegetables were raised and daily consumed, of which no record was made. The estimated value of the crops produced was from twelve to fourteen thousand dollars, to say nothing of the potatoes that were eaten before they had attained any considerable size. The entire cost to the committee was thirty-six hundred dollars, a sum that was made up by subscriptions. "Should the experiment be continued, it is best to get tracts of as many in a piece as possible, and, if poor land, to collect the sweepings of the streets to be put upon the land in the spring or carry it upon the land from time to time as collected to enrich the soil. . . It is believed that with the experience gained this year, the plan could in many respects be improved and the cost greatly reduced by beginning it in time. The committee finds that about one third of an acre is sufficient land for a family to raise enough potatoes to last them through the winter and furnish vegetables through the summer." It should be recollected that the experiment was tried under many disadvantages. It was a step in the dark; vacant city lots are in appearance the most unproductive soil imaginable; the planting was not begun till late in June, and the season was one of the worst for garden crops which the country had had for many years. Yet the success was great. A like success is claimed for a similar experiment tried in Buffalo, N. Y., in 1896. Many problems of economy, morals, and good taste would be solved if the system should become general and permanent.
Onyx Marble.—The stone called onyx marble, which is much used now in ornamental articles of furniture, is really a calcareous or lime rock, which has been deposited as a travertine or tufa from water in which it was held in solution. Water, while it can not alone dissolve lime rock, can take up considerable quantities of it when it holds carbonic acid in solution, but must drop it again when the carbonic acid has escaped. Both these processes are of common occurrence, and hence, in the springs where they are going on, tufas or travertines are formed. We know this much of what takes place, but we do not know, says Mr. George P. Merrill, in his paper on this subject, just what are the conditions governing the compactness and condition of crystallization of the deposit—why in some cases it should be susceptible of an enamel-like polish, and in others should be light and tufaceous. Onyx marble is also found in caves as a constituent of the stalagmites and stalactites which grow there, and much in the same way as in the springs. Water charged with carbonic acid percolating through the roof of the cave brings down dissolved limestone, hangs in drops to the roof, is evaporated or loses its carbonic acid, and leaves a calcareous deposit to be enlarged by continuous accretions. It rarely happens that all the water evaporates from the ceiling of the cave. Some of it usually falls to the floor, whence it is in its turn evaporated and leaves there a continually growing deposit—a stalagmite. As the water in percolating through the roof dissolved only the pure lime carbonate, or took up only a trace of impurity, these stalactitic and stalagmitic deposits are of purer lime, refined and recrystallized under new conditions. It follows almost from necessity from their mode of origin that the beds of onyx marbles, both spring and cave deposits, are as a rule far less extensive and regular in their arrangement than are the ordinary stratified and imbedded marbles. Spring action is more or less intermittent, and the place of discharge, as well as the character of the deposit, is variable. The deposit usually takes the form of a comparatively thin crust, conforming to the contours of the surfaces on which it lies. The various layers thicken and thin out irregularly, and are often lenticular in cross-section. Sound and homogeneous layers of more than twenty inches in thickness are not common. A marked and beautiful feature of the onyx marbles in general, and particularly of those which originate as spring deposits, is the fine, undulating parallel bands of growth or lines of accretion shown on a cross-section, which are due to its mode of origin through successive depositions upon the surface. The stone owes
