The sands of Haarlem are all more or less of this nature, and contain saline and sulphurous particles of matter; the under stratum of peat or derry prevent these from being absorbed into the ground. The sand also contains particles which collect in some places and form a very thin stratum of hard black matter, like that with which some minerals are coated, and this is not less injurious to vegetation than is the derry.
The great success the Dutch growers have had in cultivating bulbs which cannot be successfully propagated elsewhere is very much due to the presence of this sand, deposited by the sea on a matter which, fortunately, water cannot penetrate.
To return to the three heaps,—sand, cow-manure, and leaf-mould,—the sand is placed in large heaps to “ripen,” rather perhaps to lose some of the moisture. The growers from the three compose one general mass, which they arrange in the following order: _First_, they make a layer of sand; _second_, of manure; and _third_, of leaf-mould eight or ten inches deep; they then begin again making more layers in the same order, until their mass is six to seven feet high. The last layer is manure, but as this is apt to harden in the sun, they throw a little sand on the top. When this compound has fermented, six months, sometimes rather longer, it is mixed up and another heap is made, which is, however, again unmade and thoroughly remixed. When this soil has remained a few weeks to settle, it is carried to the beds, where it is laid to the depth of something like three feet.
George Voorhelm, in his book upon hyacinth culture, says that this manure should be composed of _three-sixths_ of cow-manure, _two-sixths_ of sand, and _one-sixth_ of leaf-mould or of tan, and he for his part preferred fresh manure to that which had been kept a year (to ferment?). He especially warns amateurs against using horse, mule, pig, or sheep manures; also he cautions them against using mud or cold earth drawn from wells, or basins where the standing water and mud have to be occasionally cleaned out; also against any powdered stuff or manures picked up with dust from the street. He quotes persons who compose their soil of tan (which has already been in use and nearly lost its heat) with cow-manure and leaf-mould, using no sand at all.