*faj 19.1867. ] 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
391 
them when grown in a moderately warm temperature only, and 
well supplied with water at the roots, besides which their leathery 
foliage is easily washed, and does not, like that of so many other 
Ferns, suffer from the effects of tobacco, if the plants should be 
subjected to it to destroy any insect with which they may occasion¬ 
ally and temporarily be troubled. During the hot summer days, 
or at any time when the temperature of the house in which they 
are grown is above 70°, Marattias and Angiopteris derive a great 
benefit from having their foliage syringed once or twice a day with 
water of about the same temperature as that of the air of the 
house. —Tiieo. 
CURRANT BUD MITE. 
We have received several examples of Currant shoots infested with 
the mite known as Phjtoptus Ribis, and therefore reproduce an illustra- 
tration we gave some time ago depicting the condition of the buds so at¬ 
tacked. We do not know any means of eradicating the pest except by 
Fig. 63—"Knotted” Currant Shoot-'. 
cutting down the infested bushes and encouraging fresh growths from 
the base, but probably the best plan is to root out the trees, burn them, 
and obtain fresh ones from another source. 
SILICA IN SOILS-ARTIFICIAL MANURES. 
I should have replied to Mr. Abbey’s communication before 
(page 339), but being from home did not get the Journal in time to allow 
of my doing so. Mr. Abbey says Dr. Voelcker gives an analysis of clay 
soil containing 84 per cent, insoluble and 1£ per cent, soluble silica, and 
he, Mr. Abbey, concludes tluit the current crop removes this soluble 
silica ; and he asks where succeeding crops get their soluble silica from ; 
and he concludes by saying that if we keep on removing the soluble 
silica from the soil, and do not replace it, that we shall ultimately 
exhaust the soil of its soluble silica. 
Now, let us calculate what 1J per cent, of soluble silica amounts 
to per acre. Assuming that a cubic yard of soil weighs 1 ton (I think 
this is about the weight, but half a ton will answer my purpose quite as 
well), then an acre of land 1 yard deep of the clay soil in question will 
weigh 4800 tons ; taking the top or first 6 inches of this we get 800 tons ; 
1J per cent, of this gives 12 tons, so we have 12 tons of soluble silica to 
work on. Mr. Abbey removes from his land two loads of hay per acre ; 
the ash from a ton of hay (Mr. Abbey’s loads are not tons, but I can 
afford to treat them as such), amounts at the outside to one-tenth of the 
whole, which is 224 lbs. Two-thirds of this (150 lbs.) is silica, so that 
Mr. Abbey actually removes with each crop of hay 300 lbs. of silica. 
“ But,” Mr. Abbey will say, “ in eighty-nine years all the soluble silica 
will be gone, except we replace it.” If it were necessary—which it is 
not —to replace silica, the easiest and best way would be to cart on road 
scrapings. We do not need to go sixteen miles for them either, and 
they are not as a rule an expensive form of manure. But how is this 
sjluble silict t) be mile soluble ? Mr. Abbey says by means of the 
acids in the manure, and he gives that as his reason for applying such 
manure. But Nature has more than one way of doing things. Here is 
another way :—“ Among the earthy constituents of soils there often 
exist fragments of felspar and other minerals derived from the granitic 
and trap rocks, as well as portions of the slaty and other beds from 
which the soils have been formed, and which, as they crumble down, 
yield more and more of those inorganic substances on which plants live. 
The decomposition of these minerals and rocks proceeds more or less 
rapidly under the conjoined action of the oxygen, the carbonic acid, and 
the moisture of the atmosphere.—(Johnston).” Now see what a store of 
silica we have in the soil to gradually become soluble. 
Mr. Abbey is farming, and he manures grass land every second year, 
and the crop following the manure is more vigorous than the second 
crop. I can understand that, but I cannot understand what follows, 
for Mr. Abbey says in effect that the unmanured crop averages the same 
quantity as the other, and is worth more money. I cannot see how this 
result would repay anybody for carting the manure sixteen miles. Mr. 
Abbey goes on to describe thriving farms which are entirely worked 
with farmyard manure. I do not doubt that farmyard manure will 
keep land in good heart; but I doubt the result being due to silica, and 
where farmers do not think it worth the trouble to study the question 
of artificials, so as to put in what is required, they had better keep to 
farmyard manure. I quite agree with Mr. Abbey, that the use of arti¬ 
ficials, or those of them which are simply “ patent exhausters,” to the 
exclusion of farmyard manure is a mistake. I never said it was not so. 
But if, on the other hand, science gives us artificials, by means of which 
we can reap a double harvest, or something very like it, each year, •with 
one sowing, one reaping, and all the other expensive operations of farm¬ 
ing, I think any person who does not avail himself of the assistance of 
science is foolish. There is as much difference between the old-fashioned 
style of farming and the scientific method as there is between the coach 
of days gone by, crawling over the weary road, and the express train of 
to-day, flashing past like a whirlwind. 
“ What is the value of silicates ? ” Mr. Abbey asks. Well, silicates 
are valuable for what the silica is combined with. Thus: silicate of 
lime is valuable because of the lime ; silicate of potash because of the 
potash ; silicate of soda because of the soda, and so on. But what is 
the value of silica alone—by itself ? It is just as valuable as the paper 
in which we wrap up a pound of butter, or a packet of tea, or a pound 
of rumpstealc. The very fact of the animal rejecting the whole of it 
from its food shows that it is no use to it. In the ground it acts simply 
as drainage, or combines and holds other more valuable constituents, as 
potash, lime, Ac. ; while in the plant, Nature uses it as an outer skin or 
covering to protect the leaves from injury, and to strengthen the straw 
of grass and cereals. Man uses it for mending roads and glazing pottery 
with principally, but it is contained only in the hair of his head, and 
there only in a very minute quantity. 
I have always been led to believe, and I think all the authorities are 
with me, that farmyard manure is valuable because it contains phos¬ 
phates, nitrates, saline and vegetable matters—in others words, organic 
and inorganic manures. If this is not so there are many readers of the 
Journal who are labouring under the same delusion that I am, but we 
err in good company. Were it possible for Mr. Abbey to let me have 
all the phosphates, nitrates, Ac., from the manure he uses, he, in return, 
would be quite welcome to all the silica in mine, and all the road scrap¬ 
ings in the parish to boot. 
We can trace the really valuable parts of manures in the bodies of 
men and animals. The fat is carbon, which the plant draws from the 
atmosphere and the soil ; the 1 ones are phosphate of lime and phos¬ 
phorus, from the phosphates and lime of the manures. The flesh con¬ 
tains potash, the blood salt, while the lean meat and muscle are made 
up of nitrogen from the nitrates of the manure. But where is the 
silica ? As well ask where is the paper we wrapped the butter in. 
Mr. Abbey objects to my saying, “ I look forward to the production 
of Roses and other crops by means of artificial manures.” He should 
remember that I do not expect this until such times as we shall 
have ascertained exactly what Roses and other crops arc made of. 
When I know as much about the constituent parts of Roses as Dr. 
Voelcker knows about Wheat, I shall be able to grow Roses just as 
easily as Wheat is grown at Sawbridgeworth. That is my opinion, at 
any rate. I never have made experiments with artificials alone, because 
my light sandy soil does not admit of such treatment; this is why 1 
have used farmyard manure, and still continue to use it. Mr. Abbey 
asks “ If I think it is a fair experiment to first make ground fertile 
with farmyard manure, and then to begin experiments on it ?” and he 
