— 
nw 
CONCRETE. 
of the persons who let land on this system are 
middle-men ; and all, or very nearly all, the per- 
- sons to whom it is let are cottiers, very small 
farmers, or parties in a state of extreme penury. 
The rent is exorbitant,—sometimes fivefold or 
| sixfold the real value; the pieces of land let are, 
in general, very small,—sometimes one or two 
roods or even but a few perches; the kind of land 
let is sometimes old pasture, sometimes rich ley, 
and generally such as contains a large proportion 
of mould and grassy fibre; the general course of 
cropping is first two successive years of potatoes, 
and next a constant round of corn till the ground 
will no longer repay seed and labour; the usual 
| georgical treatment is uniformly to apply no 
_ manure, and occasionally to pare and burn; and 
_ the common consequences are the conversion of 
some good land into comparative wilderness, the 
reduction of most land to temporary exhaustion 
and uselessness, damage to the landlord, confirmed 
penury and wretchedness to the working tenant, 
and the prolongation of the reign of agricultural 
ignorance and barbarism over vast districts of 
| one of the most beautiful and naturally fertile 
countries in the world. 
CONCENTRIC LAYERS. See Bark and Woop. 
CONCRETE. A term given to a species of hy- 
_ draulic cement, sometimes known as Jbeton or 
grubstone-mortar. In preparing concrete, the 
following proportions have been found to succeed 
perfectly in some recent structures. 
Hydraulic lime, (unslaked, ) 0°30 parts 
Sand, (middling, ) ‘ ; Oz3sO= 
Cement, (common clay, ) “ 030 — 
Gravel, (coarse, ) A Z O:20Ps 223 
Chippings of stone, 0:40 — 
The lime, sand, and cement, are, in the first 
place, thoroughly worked up into a homogeneous 
mass of a hard temper; this mass is suffered to 
rest in a heap about twelve hours; it is then 
spread out into a layer about six inches thick, 
and the gravel and stone are evenly spread over 
it, and the whole well mixed up. The mass, be- 
fore it is used, is suffered to remain until it has 
partially set, which will require from twelve to 
thirty-six hours, according to the quality of the 
mortar. This delay is found to improve the 
quality of the concrete. This material depends 
on the quality of the mortar for its excellence. 
It is not stronger than simple hydraulic mortar, 
but it is far more economical. The gravel, which 
enters into its composition, is used to fill up the 
voids between the fragments of stone, which 
would otherwise be filled by the mortar alone. 
Broken brick may be used instead of fragments 
of stone when the latter cannot be had; or gravel 
alone may be used. 
CONCRETION. See Carcunus. 
CONDITION. Healthiness, strength, energy, 
and fine appearance in a horse. Condition im- 
plies not merely plumpness and sleekiness, but 
such a degree of high, healthy vigour as enables 
the animal to perform extraordinary labour with- 
CONDUCTOR. 
853 
out becoming over-fatigued. Every defect with 
respect to condition originates either in bad 
grooming or in disease. 
CONDUCTOR OF LIGHTNING. An instru- 
ment, by means of which either the electricity of 
the clouds—the cause of lightning—is conducted, 
without explosion, into the earth, or the light- 
ning itself is intercepted and conducted, in a 
particular way, into the earth or water, without 
injuring buildings, ships, &c. This invention be- 
longs to Franklin. While making experiments 
on electricity, he observed that a pointed metal- 
lic wire, if brought near an electrified body, 
gradually deprives the latter of its electricity in 
such a manner that no sparks appear. There- 
fore, as clouds are electrified, he thought that 
they might be deprived of their electricity (which 
is the cause of lightning and of its striking), if a 
pointed metallic rod were fastened upon the 
highest part of a building, and a wire carried 
down from this into the earth, so that the elec- 
tricity of the cloud, attracted by the point, might 
be conducted into the ground. Franklin’s con- 
jecture proved to be well founded, and conduc- 
tors were soon after introduced into many coun- 
tries. They at first consisted of an iron rod, 
running down the sides of a building into the 
earth, while its point rose several feet above the 
building. Experience, thus far, shows the best 
construction of conductors to be this :—The con- 
ductor consists of a rod of iron, an inch thick, to 
the upper end of which is attached a tapering 
piece of copper, 8 or 9 inches in length, gilded, 
to prevent its rusting. This rod is fixed to the 
highest part of a building, in such a way as to rise 
at least 5 or 6 feet above it: to this are fastened 
strips of copper, 3 or 4 inches broad, and riveted 
together, which must reach to the earth, and be 
carried into it about a foot deep. The strips are 
to be carefully nailed upon the roof and against 
the wall of the building. The first conductors in 
Europe were erected at Payneshill, in England, 
in 1762, and upon the steeple of St. James’ church, 
at Hamburg, in Germany, in 1769. In modern 
times, conductors have been proposed to super- 
sede those formerly in use. Among them is the 
cheap one of Nicolai, made of strips of tin, which 
has already been used; for instance, at Lohmen, 
near Pirna. Millington says, “No rod of iron 
less than # of an inch in diameter, should be 
used, but an inch will be better. Both the upper 
and lower ends should terminate in sharp points, 
because electricity is known to enter and to 
leave points with less violence than any other 
shape; and as the upper point, from its constant 
exposure to all weathers, soon decays, and is 
sometimes melted by a stroke of lightning, it is 
best to protect it by forming it of some good 
conducting substance that is nearly imperishable, 
and charcoal, solid plumbago or black-lead, and 
the metal platinum, are best suited to this pur- 
pose, the last being the best ; and as the quantity 
of platinum is not necessarily large, the expense 
