178 
THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, June 28, 1859. 
THE SCIENCE OF GARDENING. 
{Continued from page 168.) 
In affording warmth to plants, we have seen that the earth is 
of considerable importance; and the power of accumulating and 
retaining heat varies as much in soils as the proportions of their 
constituents. Sir Humphrey Davy found that a rich black 
mould, containing one-fourth of vegetable matter, had its tem¬ 
perature increased in an hour from 65° to 8S° by exposure to the 
sunshine, whilst a chalk soil was heated only to 69° under similar 
circumstances; but the first, when removed into the shade, 
cooled in half an hour 15°, whereas the latter lost only 4°. This 
explains why the orops on light-coloured tenacious soils are, in 
general, so much more backward in spring, but are retained 
longer in verdure during autumn, than those on black, light soils ; 
the latter attain a general warmth the more readily, but part 
from it w ith equal speed. 
M. Schubler has examined these phenomena more, and pub¬ 
lished the following tables. “ The first,” he says, “ contains the 
results of a series of experiments which I made on the different 
degrees in which earths acquire warmth from the sun in fine 
weather. I placed these earths in vessels of four square inches 
in surface, and half an inch deep, and exposed them to the rays 
of the sun, coloured differently on the surface, and furnished 
with thermometers. The observations were made in the latter 
part of August, and between 11 and 3 o’clock in the day, while 
the temperature of the air varied in the shade from 72to 77° E. 
As all the observations could not be made at once, the tem¬ 
perature which sand acquired on the same occasion was in each 
case taken as the standard of comparison, to which all the several 
observations have been reduced, 
Kinds of earth. 
Mean of highest temperature of the 
upper surfaces of the earths. (77° F. 
in the shade,) 
With a surface of 
the natural colour. 
With dry earth. 
With a 
With a 
Wet. 
Dry. 
white 
black 
surface. 
surface. 
Degrees. 
Degrees. 
Degrees. 
Degrees, 
Siliceous sand, bright yellowish 
grey. 
Calcareous sand, whitish grey . 
99.1 
112.6 
109.9 
123.6 
99.3 
112.1 
109.9 
124.0 
Gypsum, bright white-grev. 
97.3 
110.5 
110.3 
124.3 
Sandy clay, yellowish . 
98.2 
111.4 
108.3 
121.6 
Loamy clay, yellowish . 
99.1 
112.1 
107.8 
121.1 
Stiff clay, or brick earth, yel- 
lowisti grey . 
99.3 
112.3 
107.4 
120.4 
Fine bluish grey clay. 
99.5 
113.0 
106.3 
120.0 
Lime, white. 
96.1 
109.4 
109.2 
122.9 
Magnesia, pure white . 
95.2 
108.7 
108.7 
121.3 
Humus, brownish black . 
103.6 
117.3 
108.5 
120.9 
Garden mould, blackish grey .. 
99.5 
113.5 
108.3 
122.5 
Arable soil, grey. 
97.1 
111.7 
107.6 
122.0 
Slaty marl, brownish red. 
101.8 
115.3 
108.3 
123.4 
“The next table contains the results of trials made to de¬ 
termine the extent of the power possessed by different soils of 
giving out to surrounding bodies, in different lengths of time, 
the warmth communicated to them by the sun or the temperature 
of the atmosphere:— 
Kinds of earth. 
Pow er of re¬ 
taining heat, 
that of calca¬ 
reous sand 
being = 100.0 
Length of time required 
by 30 cubic inches of 
earth to cool down from 
a temperature of 
to 70^° F. in a surround¬ 
ing temperature of 61^°. 
Calcareous sand . 
100.0 
in 3 hours, 30 min. 
Siliceous sand . 
95.6 
3 
— 20 — 
Gypsum powder. 
73.8 
o 
— 34 — 
Sandy clay. 
76.9 
2 
— 41 — 
Loamy clay . 
71.8 
2 
— 30 — 
Stiff clay, or brick earth . 
68.4 
2 
— 24 — 
Pure grey clay. 
66.7 
9 
— 19 — 
Fine lime . 
61.3 
2 
— 10 — 
Humus . 
49.0 
1 
— 43 — 
Fine magnesia. 
38.0 
1 
— 20 — 
Garden mould. 
64.8 
9 
— 16 — 
Arable soil. 
70.1 
9 
— 27 — 
Slaty marl . 
98.1 
3 
*- 26 — 
Different plants affect different soils. Every gardener must 
have observed that there is scarcely a kitchen garden but has 
some particular crop whioh it sustains in luxuriance far superior 
to any other garden in its neighbourhood, or to any other crop 
that can be grown on it. A garden we once cultivated would not 
produce, without the preparation of an artificial soil, the common 
garden Cress (Lepidium sativum), whilst the Raspberry was re¬ 
markably luxuriant; and we have seen that the composition of a 
soil has a main influence in these peculiarities. 
It is certain that a soil is often considered unproductive, and 
the unproductiveness attributed to some deficiency in its staple, 
when, in truth, the defect arises from erroneous management. We 
have before stated an instance of tap-rooted plants being pro¬ 
duced of superior size and form, by means of applying the 
manure deep below the surface. In another instance, some 
Parsnips being of necessity sown in a poor soil, some manure 
was turned in by trenching full twelve inches deep, but none 
applied to the surface ; but, at the time of thinning, half the 
plants were left at an average of twelve inches distance between 
the plants, the other half at nine inches ; when taken up for 
storing the whole were alike perfectly fusiform, but those grown 
at twelve inches apart were the finest, as four and a half is to 
three. If manure had been applied to the surface, the fibrous 
roots, it -was calculated, would be multiplied at the expense of 
the caudex, to its much greater detriment, than by making the 
few, usually produced by this root, extend in length by enlarging 
the circuit of their pasturage. 
Again, a more siliceous, darker-coloured soil should be employed 
for the growth of an early crop of any given plant than is re¬ 
quired by the main crop ; because such soil will more readily get 
rid of the superfluous moisture, and earlier acquire a genial 
warmth—two great desiderata for vegetation in spring. On the 
contrary, in autumn, for a late crop of Peas, for instance, the soil 
should be more aluminous; because in August and September, 
atmospheric moisture, in the form of night-dews, abounds : the 
foliage is, therefore, perpetually subject to alternate extremes of 
moisture and dryness, whilst the root is liable to a state of ex¬ 
ceeding drought. The soil, therefore, should be rich, and kept 
in a minute state of division by frequent koemg, that moisture 
may be absorbed; and it should be more aluminous, that such 
moisture may be retained.—J. 
FERN CULTURE. 
In copying my sketch, forwarded with the communication given 
in your number for April 26 (No. 552), the artist ha3 taken tlie 
license of altering it, which needs some explanation, as it is neces¬ 
sary to point out the error he has fallen into ; because it involves 
one of the most important elements of success in growing Perns 
in confinement, and which, as there represented, is an invariable 
source of failure. 
My intention was to represent the section of a common dinner 
plate (not a soup plate), shewing the surface of the sand level 
with the inner edge of the rim, and the soil placed above it, and, 
consequently, higher within the glass than the edge of the plate 
upon which the glass rests. This little circumstance, although 
apparently £0 trivial, makes all the difference between success and 
failure ; for when planted lower than the edge of the plate, the 
surface of the soil and all upon it become enveloped in a damp 
and stagnant atmosphere; and mouldiuess, damping off, and the 
plants becoming unhealthy are the invariable consequences. This 
is one of the principal reasons why Perns so seldom continue long 
in good condition when grown in the deep glass pans usually 
sold for that purpose. 
When either seedlings are to be raised, or Perns grown under 
a glass shade, and kept either in a sitting-room or in an ordinary 
greenhouse, the glass cover should be pressed do .vn into the soil, 
upon the edge of the plate, and then, by keeping the small portion 
of 6oil outside moderately clamp, it will prevent the soil, or the 
atmosphere within, from getting either too wet or too dry. The 
dryness or amount of moisture in tlic air of the room in which 
they are kept has very much to do with success, as, the more 
moisture the air may contain, the less wet will be required on the 
surface of the soil; but this will be fully explained when speaking 
of ventilation and circulation of the air. Por our present pur¬ 
pose—that is, in raising seedlings, if kept in the house, they must 
not be placed at or near an open window, but in a corner, a recess, 
or in a window with the upper sash only to be opened. By’ far 
the best place is a small pit sunk a few inches below the surface 
of the ground, and a shallow frame covered either with a glazed 
sash or oiled paper. The floor and the cover should both slope 
to the north, and at such an angle that the sun may shine upon 
the lowest part of the floor. To prevent the air which is enclosed 
