It is somewhat extraordinary, that a process similar to the composition of the Loriot.mortar is described in A Treatise on Building in Woter,by George Semple, printed in Dublin, 1771i. In discoursing on the good of the roach lone of Ireland, Mr. Semple remarks, that "it has sonic useful qualities, not much known among the generality of workmen. As, for instance, our lime-stone will make exceeding good terras for water-works, for which purpose you :11'0 to prepare it thus : get your roach-lime brought to you hot from the kiln, and immediately pound, or grind it with a wooden maul, on a smooth large stone, on a dry boarded floor, till you make it as fine as flour; then, without loss of time, sift it through a coarse hair or wire sieve, and to the quantity of a hod of your setting mortar (which on this account should he poorer than ordinary) put in two or three shovelfuls of this fine flour of the roach-lime, and let two men, for expedition's sake, beat them together, with such beaters as the plasterers make use of and then use it immediately. This, I can assure you, will not only stand as well, but is really preferable to any terras." The memoir of N. Loriot was published in 1774, only two years previous to this treatise of Setnple, who appears to have been a man rather of practice and experience than of reading; and, besides, in the book quoted from, he expressly, though incidentally, mentions his ignorance of the French language. We are justified, therefore, in stating that the knowledge of the advantages of mixing quiek-lime powder in mortar, was not confined to M. Loriot, though it might have been an original invention in him, and that he was the first who drew the public attention to the process, and used it in any considerable works.
We have now to notice the valuable Treatise of M. Vicat, the celebrated French engineer, on the Composition of Mor tars and Cements. This scientific and elaborate work has been made extensively known in • this country, by the able manner in which it has been translated by Captain J. T. Smith, of the :Madras Engineers. The labours of this gen tleman have given increased value to M. Vicat's work, and the numerous notes, tables, and other information, added to the original work by Captain Smith, will he found most use fid to the professional man, and well worth his careful and attentive study.
In this place we shall briefly describe the mode pursued by N. Vicat in the manufacture of the Artificial Hydraulic Limes, he so strongly recommends. We shall have occasion to return to his work hereafter, when on the subject of CONCRETE.
The practice of M. Vicat seems to have been principally directed to the adoption of the hydraulic limes, in preference to the more energetic cements so generally used in this country, but his investigations have been conducted on so compre hensive a scale, that the processes laid down b? him for the manufacture of artificial hydraulic compounds are capable of application to almost every requirement of the Architect or Engineer, or to almost every situation.
The opinion so decidedly expressed by M. Vicat, that the superior adhesion of the hydraulic limes, must inevitably lead to their general adoption in this country, in preference to our (so-called) Roman cements, has been much combated by practical men. It may be said, without entering into a dis cussion of the question, that it appears to be one on which a contrariety of opinion may be occasioned by a difference of situation and circumstances. Thus, in comparing the merits of the two systems, it is important to consider, that, in one, the means of minute mechanical division are an essential element, in the other that it is unnecessary ; and that this element, which in one situation may be obtained at a cheap rate, in another may be expensive and unattainable.
The hydraulic limes, therefore, which do not require to be ground previous to use, are at all events most suitable for those situations where the facilities of mechanical agency can not be resorted to, while the ground cements are better adapted to the vicinity of a large capital, where it is of little importance that the builder becomes dependent upon others for his supply.
The difference, in fact. consists in this, that the ground cements, of whatever kind, will ever be furnished by manu facturers, whereas the hydraulic limes may at all times be prepared by the common workman, without machinery, and at a owst not much exceeding that of common lime.
The wleseription given by M. Vicat of the mode in which the artificial hydraulic limes are prepared is as follows: — "The artificial hydraulic limes are prepared by two methods: the most perfect, but alsothe most expensive, consists in mixing with rich lime slacked in any way, a certain propor tion ()relay, and calcining the mixture; this is termed arti ficial lime twice kilned."
" the second process, we substitute for the lime any very soft calcareous substance (such, for instance, as chalk), which it is easy to bruise and reduce to a paste with water. In this %V:Iy a great saving is effeeted, but at the same time is procured an artificial lime of good quality, though not equal to that derived from the first process, in consequence of the rather less perfect amalgamation of the mixture." NVe see that by being able to regulate the proportions, we can also give to the factitious lime whatever degree of energy we please, and cause it at pleasure to equal or surpass the natural hydraulic limes." We usually take twenty parts of dry clay to eighty parts of very rich lime, or to one hundred and forty of carbonate of lime. This refers to the lime in the unslacked condition, or to the wine:whined mineral. If the lime he slacked, the proportion should be increased to 110 parts. But if the lime or its carbonate should already he at all mixed with clay in the natural state, then fifteen parts of clay will he sufficient. Moreover, it is proper to determine the proportions for every locality." The mixture here described," adds Captain Smith in a note, " is such as to produce the hydraulic limes, whose properties are similar to the Aberthaw, the analysis of which shows it to correspond nearly with the proportions reponunended. as it consists of S6.2 of carbonate of lime to 11:2 clay, (with 2.6 water and carbonaceous matter), being at the rate of 1S.2 parts clay, to 140 of the carbonate of lime. The cements now in use in England. are much quicker setting than these, and differ in being unslacked. They con tain a greater proportion of clay, hut may be manufactured artificially with equal ease. by combining such relative quantities of chalk, or lime, and clay, as will snit the purpose intended. Parker's Patent Cement, as analyzed by Sir Humphrey Davy, contains 45 per cent of clay to 55 carbonate of lime ; the Yorkshire cement, 34 clay to 62 carbonate of lime ; the Sheppey, 32 clay to 06 carbonate of lime ; and the Harwich, which is a quieker-settin7 cement, 47 clay to 49 carbonate of lime." It seems to be evident from the experiments of M. Vicat, that the manufacture of artificial cements may he almost infinitely varied by the admixture of diGrent ingredients. The character, quality, and propor tions of these must he the result of actual practice and experiment. for so different may be the chemical properties of apparently similar materials, that no results, however successful in one locality, can be trusted to with certainty in another. It is only necessary to add, that in all eases, attention should be paid to the perfect amalgama tion of the materials; and the degree of calcination best suited to it should be carefully observed, before attempting the manuthetnre on a large The process made use of at a manufactory of artificial lime at Mendon. near Paris, is thus described by AI. Vieat—" The materials made use of are chalk of the country, and the clay of Vaurigard, which is previously broken up into lumps of the size of one's fist. A millstone set up edgeways, and a strong wheel with spokes and felloes, firmly attached to a set of harrows and rakes, are set in motion by a two-horse gin, in a circular basin of about two metres (six feet and a half English) radius. In the middle of the basin is a pillar of masonry, on which turns the vertical arbor to which the whole system is fixed : into this basin, to which water is conveyed by means of a cock, they throw successively flair measures of chalk, and one measure of clay. After an hour and a halt' working, they obtain about 1.50 metres cube (nearly 53 cubic, feet English), of a thin pulp, which they draw off by means of a conduit pierced horizontally on a level with the bottom of the basin. The fluid descends by its own weight; first into one excavation, then into a second, then a third, and so on to a font th or fifth. These communicate with one another at top ; when the first is full, the fresh liquid, as it arrives, as well as the supernatant fluid, flow over into the second excavation; from the second into the third, and so on to the last, the clear water from which drains off into a cesspool. Other excavations, cut in steps like the preceding, serve to receive the fresh products of the work, whilst the material in the first series acquires the consistency necessary for moulding. The smaller the depth of the pans in relation to their superficies, the sooner is the above-mentioned consistency obtained.