240 
THE CULTIVATOR. 
Aug. 
purposes. To give an instance of this, Kittle in As- 
cltaffenburg, examined a series of limestones from 
the Spessart, and found in four different places in the 
neighborhood, limestone, which yielded a very tolerable 
mortar, and two varieties which were excellent. Hy¬ 
draulic lime has occasionally been met with in the same 
quarry as fat lime; and its nature not having been in¬ 
vestigated, has been neglected as useless in conse¬ 
quence of the slowness with which it is slaked. 
AH artificial or natural hydraulic limestones are solu¬ 
ble (before as well as after calcination) in muriatic 
acid, with the separation of silica, except when sand 
or some similar substance has been added to them. 
Practical Remarks .—The hydraulic limestones, when 
hey do not contain a sufficient quantity of lime to be 
iapable of slaking with water, must be very finely pul- 
tensed; it is only by this high state of division that a 
jroper action can ensue. A thorough penetration of 
;he siliceous portion by the lime is never entirely effect- 
id, but a certain proportion remains enclosed and remo- 
red from the sphere of action. 
One point, which is very often neglected in preparing 
artificial hydraulic mortar, is the attention to the pro¬ 
per proportion between the slaked lime and cement. 
Both the ingredients must be mixed by measure or 
weight, and not merely estimated by the eye. 
The best plan is to moisten the necessary quantity of 
cement first, and then mix the freshly slaked lime with 
it. The more uniformly and intimately both are mixed, 
the better is the result. 
The hydraulic mortar employed in building the Eddy- 
stone lighthouse, was mixed by Smcaton from equal 
proportions of lime, slaked to powder, and Puzzolana. 
Trass and Puzzolana are generally mixed with half 
their weight of lime, as was the practice amongst the 
Romans. It is desirable to ascertain the best propor¬ 
tions by experiment in all cases where no certain know¬ 
ledge of the nature of the two substances can be ob¬ 
tained. 
Good hydraulic mortar, whether made from natural 
limestone or composed of lime and cement, should not 
show any tendency to crack when hardened under wa¬ 
ter, even when no sand is mixed with it. It then forms 
a very dense and solid mass, which, in a short time, 
neither suffers water topermeate it, nor is attacked by the 
water, but acquires a considerable degree of hardness. 
For this reason, it is well to use nothing but hydraulic 
mortar for those parts of walls which are constantly 
under water. If the mortar is not only required to har¬ 
den, but also to bind well, a very important point must 
never be neglected, and that is to moisten the surfaces 
of the stones to which the mortar is to be applied. 
When this is not done, the surface of the stone (by its 
power of absorbing moisture,) dries the mortar and 
prevents proper adhesion from taking piace. The 
joint then remains open to a greater or less extent. 
It does not by any means follow, that because hy¬ 
draulic mortar is the only durable material for building 
under water, it cannot consequently be used for dry walls. 
It is, on the contrary, of the greatest service wherever 
protection is required against the infiltration of moist¬ 
ure and damp; and dwellings or buildings can often be 
rendered very much less damp by a judicious applica 
tion of a hydraulic coating; a layer of this kind, when 
once hardened, is not calculated, like ordinary mortar, 
to attract moisture and allow it to pass through. The 
hydraulic mortar must, of course, when used for cover¬ 
ing dry walls or otherwise, be kept moist and watered, 
until it has acquired its proper degree of hardness. If 
this is not attended to, a soft, friable, useless coating is 
the certain result. If moisture enters from below, for 
instance, between the wall and the coating of mortar, 
it will continue confined there inconsequence of the im¬ 
penetrability of the latter, which, on the occurrence of 
a frost, will most certainly peel off and be destroyed. 
Care must also be taken that the mortar does not dry 
up of itself immediately in the air, in which case it 
contracts and cracks. It is, therefore, necessary to 
add sand or some other substance which obviates the 
shrinking. Hydraulic mortar will bear a very conside¬ 
rable quantity of sand without injury to its hardness, 
even as much as one and a-half times its own weight 
and more. This addition therefore, is important in an 
economical point of view. The grain of the sand em¬ 
ployed, however, requires attention, as was the case 
with ordinary mortar; sharp, angular sand is decidedly 
preferable to blunt, rounded sand, and it is better to use 
a mixture of coarse with fine sand, than that the sand 
should be all of the same sized grain. The sand should 
likewise be as free as possible from earthy particles and 
dust. In mortar composed of lime and cement, the 
rule is, to proportion the sand to the quantit}' of ce¬ 
ment used. Slaked lime will not bear more than s a cer¬ 
tain quantity of these substances, which quantity must 
not be exceeded, the cement itself being for the greater 
part inactive and playing the part of sand. 
Hydraulic mortar that sets with sufficient rapidity, 
and to which a proper proportion of sand has been ad¬ 
ded, may be employed for casting tolerably massive ob¬ 
jects, which are not subject to crack when dry. This 
enables hydraulic mortar to be employed for architectu¬ 
ral ornaments which then combine great sharpness with 
durability, are very light as compared with similar fig¬ 
ures of sandstone, and have the great advantage of be¬ 
ing easily multiplied. 
A similar application is that for casting water-pipes, 
on the spot where they are required, as proposed by 
Gasparin. The mould employed is a linen hose, like 
those attached to the fire engines, a few meters in 
length, which is filled with water and closed at both 
ends. A thick kind of bolster is thus produced, over 
which sand is sifted, and it is then laid upon a deposite 
of hydraulic lime and covered by pouring over it the 
same substance. When the whole has hardened, the 
hose is drawn forward, about the length of one foot, be¬ 
ing left inserted in the tube, and a fresh length is cast. 
Water courses, thus constructed, must however, have a 
certain amount of fail, or the sand cannot be washed out, 
and will impede (he delivery of the water. 
When hydraulic lime is mixed with small stones, or 
with shingles from the bed of a river, or the sea, walls 
can be directly constructed of it, and a mass is obtain¬ 
ed which resembles the erections with ordinary mortar, 
and is called biton by the French. 
At Toulon, a mixture was used for the construction 
of the harbor, consisting of 3 parts lime, 4 Puzzolana, 
1 smithy ashes, 2 sand, and 4 parts of rolled stones or 
shingles. 
The great strength of walls, constructed with hy- 
draulio mortar, is most clearly shown by the experi¬ 
ments undertaken with a view to break beams construct¬ 
ed of brickwork. A 25 feet long, a"d 2i feet wide 
beam, constructed with 19 layers of bricks, bound to¬ 
gether by Roman cement, in which, here and there, pa¬ 
rallel strips of iron were enclosed, was capable of bear¬ 
ing, when supported at both ends, a weight of 22 tons 
suspended from the middle, before it showed any signs 
of fracture. 
Shoeing Horses. —At. a meeting of the Royal Agri 
cultural Society of England, Professor Sewall remark 
ed, that he frequently found old horses shod with a lay 
er of leather, forming an artificial sole between the 
hoof and the shoe, recovering from severe affections, 
causing injury to the hoof—such, for instance, as con¬ 
traction, brittleness, and cracks, or even diseases of the 
foot itself, as thrushes, oorns, cankers, etc., and per¬ 
manently regain their original elasticity and firmness. 
