IN the spring of 1870, I had the superintendence of planting some 200 trees of various kinds in and around our public grounds. The spring and succeeding summer was one of unusual and excessive drouth. About eighty of these trees, White Elm, Soft Maple, American Linden, Catalpa, etc., were planted on the side-walks for street trees ; they were on an average ten and fourteen feet high. They were planted in a rather poor clay soil (mixed in planting with a rich, black, sandy loam), and within a few inches of the curb stones; the gutters being shallow and well bouldered. The walk was covered with about four inches of gravel. Every one of these trees grew finely, many of them making a growth of branches two or more feet in length. Some of the elms when planted, seemed almost dead, but they started and grew well. None of them were watered artificially. The same kind of trees planted within the enclosures in much better soil, but without the gravel mulch, grew very little; many of them, probably half, died, notwithstanding constant care in watering, deep and well drained soil, shortening in mulching with grass and litter, etc. The same fate attended more than half the trees planted by others all over the country.

Hence, I conclude that gravel and small stones are unsurpassed as a mulch.

They allow the rains to readily penetrate the soil, retain moisture, absorb heat and equalize the temperature. The practical utility of gravel as a mulch, where it can be easily procured, should be tested by all tree planters. It will not injure heavy clay soils, at least, but will be beneficial. R.