FRAGMENTS OF SCIENCE. 



283 



people themselves, under the supervision of 

 the committee ; about nine tenths of the 

 pieces were well taken. care of. The com- 

 mittee estimate that the potato crop aver- 

 aged 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 rec- 

 ord was made. The estimated value of the 

 crops produced was from twelve to fourteen 

 thousand dollars, to say nothing of the pota- 

 toes 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 expe- 

 rience 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 disadvan- 

 tages. It was a step in the dark ; vacant 

 city lots are in appearance the most unpro- 

 ductive 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 ornamen- 

 tal articles of furniture, is really a calcare- 

 ous 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 occur- 

 rence, 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 de- 

 posit why in some cases it should be sus- 

 ceptible of an enamel-like polish, and in 

 others should be light and tufaceous. Onyx 

 marble is also found in caves as a constitu- 

 ent 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 evapo- 

 rates 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 sta- 

 lactitic 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 len- 

 ticular in cross-section. Sound and homo- 

 geneous layers of more than twenty inches in 

 thickness are not common. A marked and 

 beautiful feature of the onyx marbles in gen- 

 eral, and particularly of those which originate 

 as spring deposits, is the fine, undulating par- 

 allel bands of growth or lines of accretion 

 shown on a cross-section, which are due to 

 its mode of origin through successive depo- 

 sitions upon the surface. The stone owes 



