334 



NEW ENGLAND FARMER. 



parinw artificial hydraulic mortar, is the attention to 

 the proper proportion between the slaked lime and 

 cement. Both the ingredients must be mixed bj' 

 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 

 Eddystone lighthouse, was mixed by Smeaton from 

 equal proportions of lime, slaked to powder, and puz- 

 folana. 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 proportions by experiment in all cases where 

 no certain knowledge of the nature of the two sub- 

 stances can be obtained. 



(lood hydraulic mortar, whether made from natu- 

 ral limestone or composed of lime and cement, should 

 not ^how any tendency to crack when hardened un- 

 der water, 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 to permeate it, nor 

 is attacked by the water, but acquires a considerable 

 degree of hardiness. 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 harden, but also to 

 bind well, a very important point must never be 

 neglected ; and that is, to moisten the surfaces of the 

 atones 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 place. 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 build- 

 ing under water, it cannot consequently be used for 

 dry walls. It is, on the contrary, of the greatest 

 service wherever protection is required agaiiist the 

 infiltration of moisture and damp ; and dwellings or 

 buildings can often be rendered very much less 

 damp by a judicious application of a hydraulic coat- 

 ing ; a layer of this kind, when once hardened, is 

 not calculated, like ordinary mortar, to attract mois- 

 ture an.d allow it to pass through. The hydraulic 

 mortar must, of course, when used for covering 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 in consequence 

 of the impenetrability of the latter, v/hich, 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 sub- 

 stance which obviates the shrinking. Hj'draulic 

 mortar will bear a vei-y considerable 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 employed, 

 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 

 Band 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 

 quantity of cement used. Slaked lime will not bear 

 more than a certain 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 

 added, may be employed for casting tolerably massive 

 objects, which are not subject to crack when dry. 

 This enables hydraulic mortar to be employed for 

 architectural ornaments, which then combine great 

 sharpness with durability, arc very light as com- 

 pared with similar figures of sandstone, and have the 

 great advantage of being easily multiplied. 



A similar application is that for casting water- 

 pipes, on the spot where they are required, as pro- 

 posed 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 deposit 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, being left inserted in 

 the tube, and a fresh length is cast. Watercourses, 

 thus constructed, must, however, have a certain 

 amount of fall, or the sand cannot be washed out, 

 and will impede the 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 

 obtained which resembles the erections with ordinary 

 mortal-, and is called b6ton by the French. 



At Toulon, a mixture was used for the construc- 

 tion of the harbor, consisting of three paits lime, 

 four puzzolana, one smithy ashes, two sand, and four 

 parts of rolled stones or shingles. 



The great strength of walls, constructed with hy- 

 draulic mortar, is most clearly shown by the experi- 

 ments undertaken with a view to break beams con- 

 structed of brickwork. A twenty-five feet long and 

 two and a half feet wide beam, constructed with 

 nineteen layers of bricks, bound together by Roman 

 cement, in Avhich, here and there, parallel strips of 

 iron were enclosed, was capable of bearing, when 

 supported at both ends, a weight of twenty-two tons 

 suspended from the middle, before it showed any 

 signs of fracture. — Albany Cultivator. 



MANURES. 



Manures assist plants, by destroying predatory 

 vermin and weeds. This, however, is not a property 

 of animal and vegetable manures ; they foster both 

 those enemies of our crops. Salt and lime are very 

 efficient dcstroj^ers of slugs, snails, grubs, &c. It is 

 astonishing how ignorantly neglectful are the culti- 

 vators of the soil, when their crops are devastated by 

 the slug, not to dress them so as to render the sur- 

 face of the soil quite white, during a promise of a 

 few days' dr}- weather, with caustic lime. It is instant 

 destruction to every slug it falls upon, and thosCN 

 whom it misses are destroyed by their coming in 

 contact with it, when moving in search of food. It 

 is a common practice to bum couch-grass, docks, 

 gorse, and other vegetables which are very retentive 

 of life, or slow in decay : a more uneconomical, un- 

 scientific method of reducing them to a state more 

 beneficial to the land of which they were the refuse, 

 cannot be devised. In breaking up heaths, such ex- 

 uvicB are very abundant ; but, in all cases, if the 

 weeds, leaves, &c., were conveyed to a hole or pit, 

 and with every single horse-load, and with barrow- 

 loads in proportion, a bushel of salt and half a bushel 

 of lime were incorporated, it would, in a few months, 

 form a mass of decayed compost of the most fertilizing 

 quality ; the lime retaining many of the gases evolved 

 during the putrefaction of the vegetable matter, and 



