192 
PARK AND CEMETERY. 
the installation of a sub-irrigation system 
because it appeared impracticable. 
SOIL IMPROVEMENT. 
Both the topsoil and the subsoil on the 
Common varied considerably, the latter 
more than the former. The topsoil av- 
eraged about 15 inches in depth, and as a 
rule was quite good from a mechanical 
standpoint, excepting that it had become 
packed down. The subsoil varied from the 
most porous gravel to the most impervious 
clay, although the latter condition was not 
very widespread. As a rule, it was low in 
its percent of organic matter. Nowhere 
was there a serious excess of water in the 
soil, but, on the contrary, there was a se- 
rious lack of moisture almost everywhere 
during periods of scant rainfall in the sum- 
mer. 
Briefly, the scheme of soil improvement 
decided on was to increase the depth of the 
topsoil from an average of 15 inches to 36 
inches over an area within reach of the 
tree roots, and at the same time to increase 
its per cent of organic matter, available 
nitrogen, phosphoric acid, potash and lime. 
Precedent for this scheme was abundant, 
in the practice of many successful horticul- 
turists, and in incidents in nature. 
To carry out this scheme the procedure 
described in the following was in the main 
adopted, although it varied somewhat from 
time to time. 
First the topsoil was stripped to its full 
depth, and either placed in spoil banks or 
used on areas ready to receive it; then the 
subsoil was removed till the excavation 
reached a depth of three feet below the 
surface. 
The worst of this subsoil — the most grav- 
elly, the sandiest and the most clayey — was 
removed from the premises and disposed 
of. The remainder, comprising the smaller 
proportion which was considered as me- 
chanically equivalent to a lean topsoil, was 
kept and used in the back filling, being- 
loosened, areated and enriched by fertilizers 
in the process of handling. 
When excavations have been made to the 
full depth of 36 inches they were filled with 
one or more of the following mixtures, 
viz.: (a) the original topsoil with manure; 
(b) topsoil brought in from the outside 
with manure; (c) selected topsoil with ma- 
nure. The proportion of manure varied 
from one-fifth to one-third, and to each 
mixture lime and bone were added at the 
rate, per cubic yard, of between one and 
two pounds of lime and about half as much 
bone. The mixture containing the subsoil 
was used in the bottom of the excavations. 
The topsoil mentioned as being brought in 
from the outside had to be supplied to meet 
the vacancy caused by the removal of the 
poor subsoil. The filling was carried six 
inches above the original grade to allow for 
settling. 
The excavating and refilling was carried 
on in trenches, practically paralleling the 
rows of trees. The trenches were made in 
three widths, namely 30 feet, 10 feet and 5 
feet. Thirty feet was regarded as the most 
desirable width, but there were not funds 
enough available to make them all this 
width. However, comparatively few were 
made as narrow as 5 feet, very many were 
made 30 feet, and most of them were 
made 10 feet wide. The width of the un- 
excavated space between the trunks of the 
trees and ihe trenches varied with different 
trees. In the case of very small trees it 
was only 3 or 4 feet and in the case of very 
large trees it was 25 feet. In addition to 
the 36-inch deep soil improvement, surface 
soil improvement consisting of spading un- 
der manure at the rate of 50 cords to the 
acre, and raking in lime and ground bone 
each at the rate of one ton to the acre, 
was done- in the areas between the trees and 
the trenches, and also in the areas beyond 
the trenches, excepting in the case of the 
parade ground, where the larger part of the 
grass area received only a plowing, har- 
rowing and raking, and a moderate applica- 
tion of seeding down fertilizer. Also there 
were a few areas, beyond the trenches, 
where a 24-inch deep soil improvement was 
carried out similar to the 36-inch deep soil 
improvement. 
COMBATING INSECTS. 
With the exception of the leopard moth 
and the elm bark borer, the important in- 
sect pests seem to have been fairly ef- 
fectively dealt with in the past, although 
there was some evidence that, in the case 
of the tops of the tallest trees, the in- 
secticidal spray had frequently failed to 
reach them properly, thus leaving them ex- 
posed to the attacks of the elm leaf beetle, 
and perhaps accounting in part for the very 
bad and moribund condition of the tops of 
these trees as compared with the quite 
good condition of these same trees lower 
down. This fact has a bearing on the leop- 
ard moth situation and perhaps on that of 
the elm bark borer because attacks of these 
insects seem to be more fatal to weakened 
trees than to vigorous, healthy ones. 
Without going into detail, it should be 
said that the leopard moth does its greatest 
injury by girdling limbs and killing them, 
and also that its life history is of such a 
nature that, so far, no wholesale method of 
coping with it and killing a multiude of in- 
sects by one operation, as by spraying or 
destroying egg clusters or nests, has yet 
been feasible, except that of cutting down 
a tree and burning it. Therefore, short of 
this radical method, the insect can be con- 
trolled only by killing the larvae indi- 
vidually, as by cutting off the extremities 
of the young twigs and destroying the same 
by fire or otherwise in the summer, when- 
ever these are seen to harbor the larvae, 
and by killing them in their burrows in the 
wood by hooking them out with bent wire 
or by the injection of bisulphide of car- 
bon, a very costly procedure — about as 
killing potato bugs by squeezing them to 
death between the fingers would be. 
Different trees are of different degrees of 
susceptibility to its attacks, usually vary- 
ing with the kind, although, as remarked 
before, a tree of weakened vitality seems 
to suffer more seriously than a vigorous 
one ; also certain individual trees of a kind 
ordinarily susceptible to its attacks seem to 
be immune; just as certain individuals of 
the human race are immune to diseases 
which are fatal to the average run of hu- 
manity. The common European linden :s 
about the only kind of tree on the Common 
which is practically free from its attacks. 
The English elm, especially a young, vigor- 
ous one, is comparatively free from its at- 
tacks, and when attacked does not seem 
to suffer much. The Scotch elm is very 
severely attacked by the leopard moth, 
which makes deep furrows and great scars 
in its branches, but seldom girdles them, 
so that the vitality'- of the tree is not seri- 
ously affected. On the south side of the 
first tar walk, north of the wooden sanitary 
building for women, there are seven or 
more large trees, usually mistaken for Eng- 
lish elms which are of another species alto- 
gether, probably Ulmus nitens. This tree 
is quite seriously attacked by the leopard 
moth. The American elm, the tree' most in 
evidence on the Common, unfortunately is 
frequently attacked by it, with serious re- 
sults. Staghead, or death of the ends of 
the branches, a prominent and unsightly 
symptom, always precedes the death of a 
tree caused or furthered by the leopard 
moth. 
Unfortunately no determined effort was 
made to cope with the leopard moth until 
its depredations had been going on for 
some years, and it had become firmly es- 
tablished and had done a great deal of 
damage. This is hardly to be wondered at, 
since the history of a great many insect 
pests is that those concerned do not real- 
ize the gravity of the situation until matters 
have reached this stage, and then the re- 
alization comes with a shock. In times 
past, trees which showed staghead were 
treated by cutting off entirely the staghead 
limbs where they joined the trunk or 
larger branches, leaving untouched those 
branches in which the staghead was not 
conspicuous or was absent, but yet where 
the larvae were undoubtedly present; later 
on more branches were similarly cut off, 
the result being trees with a few naked 
large limbs devoid of young shoots. These 
large limbs were apparently given no fur- 
ther attention and they, too, in turn, devel- 
oped staghead, with the result that the 
trees were left in such a bad condition 
that many had to be taken down. Thus 
the measures adopted finally proved of no 
avail, and, if anything, instead of arresting 
the trouble they seemed to accelerate its 
deadly effect. The measures seemed to be 
directed mostly against the symptoms of 
