Cement, generally signifies any glutinous matter, capable of uniting and keeping substances in close cohesion. It principally de-notes .compositions employed for holding together broken glass, etc. For this purpose, the juice of gar-lic is recommended as exceedingly proper; for it is very strong; and, if the operation be performed with care, leaves very little or no mark. This is also effected, by a preparation of fresh cheese cut in thin slices, which should be boiled in different waters, and continually stirred : thus it is converted into a very tough and elastic mass, which will not incorporate with liquids. After being sprinkled with a little boiling water, and worked upon a hot stone, a small quantity of unslacked lime should be added, and the whole beat into the consistence of a paste. This composition will prove a strong and durable cement for wood, stone, earthen ware and glass: when thoroughly dry, it resists every ef-fect, of water.

There is a cement for joining glass and china, used in Germany, and which appears to be preferable to that above mentioned. It is prepared as follows: lake, by measure, two parts of litharge, one of unslacked lime, and one of flint glass ; let each be separately reduced to the finest powder, and worked up into a paste with old drying oil. Hochheimer asserts, that this compound is very durable, and acquires a greater degree of hardness, when immersed in water.

Another composition, which is successfully employed by the Ger-mans, for cementing wood, is pre-pared from pitch, mixed with bul-locks'-blood, linseed-oil, and tur-pentine. The whole of these must be put over a fire, in an iron pan, and as much brick-dust added as will make them of the consistence of a thin paste. The tub, or cask, to which this preparation is to be applied, must be perfectly dry before it is laid on ; and the chinks or crevices filled up with tow, while the cement is warm. Some melt a due portion of colophony with the other liquids, previously to the adding of the brick-dust ; by which means the composition is said to be much improved.

Cement, in building, is used to denote any kind of mortar, which is stronger than that usually employed. The cement commonly used, is either cold or hot. The former is the second above described, for cementing china, etc, which is some-times, though seldom, resorted to in the erection of walls.

The hot cement, in general use, is made of resin, bees-wax, brick-dust, and chalk, boiled together. The bricks to be conjoined are heated, and rubbed together, with cement between them. If the as-sertion of foreign writers be well-founded, there is a much superior composition for cementing stones prepared on the Continent. It consists of eight parts of pitch, four of colophony, two of minium, or very fine litharge ; two of white lead ; and one of brick-dust, melted together. Sometimes, however, the following materials are substituted for those last mentioned : Take pure quartz, reduce it to a fine powder, by means of the same freestone, to which it is to be applied; add one third part of unslackedlime, and work the whole into a paste with the whites of eggs, just before it is wanted. So effectual is this preparation, that in a few mi-nutes it will acquire the compact-ness and solidity of iron.

A cement of tolerable firmness may be obtained, by a mixture of gypsum and quick-lime, with the addition of water : this compound may prove of considerable service in making troughs for holding water, or lining small canals.

A cheap mortar, or cement, that will not crack, may also be procured, according to M. Wiegleb, by mixing three parts of the thin re-siduum after slacking the lime, with one of powdered gypsum ; but he adds, that it can be used only in dry situations.

A peculiar kind of cement is pre-pared at Madras, with which most of the buildings erected in that In-dian capital, are cemented. It consists of sand and lime, with the addition only of a small quantity of water, in which a proportion of coarse sugar has been previously dissolved. The quick-setting of this mortar, and the great hardness it acquires, can, as Dr. James Anderson has observed (in his Re-creations in Agriculture, vol. i.), only be attributed to one of these two causes, namely, either the sugar added, or the quality of the lime-stone employed at Madras.— There are some kinds of lime-stone in Britain, which afford a much better mortar than others; and this also may be the case in India. Most calcareous earths are blended with sand and other particles, in various proportions ; the quality of the mortar or cement will consequently vary, according to the nature of these different ingre-dients.

It has lately been discovered, that the scrapings of certain roads, consisting chiefly of levigated lime-stone, which is impregnated in a greater or less degree with the dung and urine of animals, form an excellent cement. For ordinary walls, these scrapings alone are frequently used; and, according to the account of Mr. Marshall (in his Rural Economy of Glouces-tershire), the proportion for the best building is about one part lime to three of those materials, collected from roads composed of limestone.

By the ingenuity of speculative men, however, several other modes of forming cements, have been contrived and successfully employed ; but the enumeration of these would necessarily lead us to a greater length than our limits will permit. We shall, therefore, only give an account of the principal Patents lately granted for the invention of various cements.

The first, is that of Mr. John "Worth, chemist, dated the 28th of May 1771, now expired; for a " Preparation, or cement, for the purpose of preserving His Majesty's and other ships and vessels from worms, etc. and for various pur-poses in agriculture and commerce." - This composition con-sists of fourteen pounds of powdered or small pieces of resin; twenty-eight of sand, sifted and washed clean from dirt or loam; three and a half of red lead ; and one pound an 1 three quarters of oil: the resin must be melted over a moderate fire, the sand and lead gradually put in, and then the oil; care being taken, when they are boil-ing, to stir them constantly till they become cold, so that the mass may be uniform. When there occasion to use this cement, the quantity required must be broken into small pieces, and a pound of what is usually denominated by the chemists, fat oil, mixed with every twelve pounds of it. As as soon as this is melted, it may be applied to the object intended, either by pouring it on, or by a brush, while boiling. The quan-tity of oil to be added to the ce-ment must also be increased, or lessened, in proportion as the com-position is required to be of a greater or less degree of hardness, or softness.

The second, was granted to Dr. Higgins, for his invention of a "Water cement or stucco for build-ing, repairing, and plastering walls, etc." The component parts of this cement, are drift or quarry sand, cleansed by washing, and carefully •trained from clay, salts, and calcareous, gypsous, or other grains less hard and durable than quartz ; after which it is dried, either in the sun, or on an iron plate in a furnace, in the manner of a sand heat. To this must be added, fourteen pounds of the newest lime-stone that can be procured; and which heats most in slacking, and slacks soonest when duly watered; dis-solves in distilled vinegar with the least effervescence; leaves as little as possible of an insoluble residuum, and contains the smallest quantity of clay, gypsous or martial matter. This must be previously sifted in a brass wire sieve, as finely as possible, and slacked, by being repeatedly immersed in, and quickly drawn out , of, a butt filled with • water, till it be made to pass easily through the sieve ; rejecting that part of the lime which is too coarse. The patentee directs to continue that process, till as many ounces have been passed through the sieve as there are quarts of water in the butt. The impregnated liquor, must stand in the vessel closely coveted up, until it becomes clear, when it should be drawn off through wooden cocks, as fast and as low as the lime subsides : being now lit Dr. HIGGINS denominates this solution, the cementing liquor. Fifty-six pounds of lime, prepared in the same manner as before, are next to be slacked, by gradually sprinkling on it the. cementing liquor, in a close and . The slacked part must be immediately sifted, and the lime, it not used instantly, kept in airtight vessels ; care being taken to reject those pieces which do not pass through the sieve. This richer lime, the Doctor calls puri/ied lime. Bone-ash is then prepared, by grinding the whitest burnt bones, which must be sifted much finer than that commonly sold for making cupels. The principal materials being thus prepared, fifty-six pounds of. the coarser sand, and forty-two of the fine sand, are to be mixed on a large plank of hard wood, placed horizontally, and spread so that it will stand to the height of six inches, with a flat surface on the plank. This must be wetted with the cementing liquor, and whatever superfluous quantities of it will not incorporate with the sand, must flow off the plank. To the wetted sand are to be gradually added fourteen pounds of the puri-fied lime, tempered in the same manner as fine mortar; with this composition are, by degrees, to be mixed fourteen pounds of the bone-ash, and the whole beaten quickly together ; as the sooner, and more perfectly these materials are tempered together, and the quicker the cement thus formed is used, the better it will answer the pur-pose. This Dr. Higgins calls the water cement coarse-grained ; it is to be applied in building, pointing, plastering, stuccoing, etc. in a similar manner with mortar; the principal difference being, that as cement is shorter, and dries much sooner than mortar, or common stucco, it ought to be worked ex-peditiously in all cases ; and, in stuccoing, should be laid on by sliding the trowel upwards on it ; and that the materials used with this cement in building, ought, when it is laid on, to be well moistened with the cementing li-quor ; which is also to be em-ployed, if necessary, in wetting the cement, or reducing it to a fluid state. When such cement is required to be of the finer sort, ninety-eight pounds of the fine sand are directed to be wetted with the cementing liquor, and tempered with the purified lime and bone-ash in the manner already described ; with this only variation, that fifteen pounds of lime are to be used instead of fourteen, if the greatest part of the sand be as fine as Lynn sand. This is called water cement .fine-grained, and is to be used in giving the last coating to, or finish-ing, any work intended to imitate the finer grained stones, or stucco : it may, nevertheless, be applied to all the uses of water cement coarse-grained, and in a similar manner. Whenever, for any of the above-mentioned purposes of pointing, building, etc. a coarser grained and cheaper sand is required, fifty-six pounds of the coarsest sand, or of fine rubble well washed, twenty-eight of the coarser, and fourteen pounds of the fine sand, are to be mixed together, and wetted with the cementing liquor, as above directed; to which fourteen pounds, or some-what less, of the purified lime, and a similar quantity of the bone-ash, are to be added ; and the whole tempered together in the manner already mentioned. When the ce-ment is required to be white, colourless sand, lime, and the whitest bone-ash, are to be select-ed. Grey sand, and grey bone-ash, formed of half-burnt bones, are to be chosen for making the cement grey. Other colours may be obtained, by employing coloured sand, or by mixing the necessary quantity of coloured talc in powder, vitreous or metallic powders, or other durable ingredients, usually employ-ed in making paint. This water ce-ment, whether coarse, or fine grain-ed , may be used in forming artificial stone, by making alternate layers of the cement, and of flint, hard stone, or brick, in the moulds of the intended stone, and by exposing the masses, thus formed, to the open air, in order to harden. When such cement is wanted for water-fences, two-thirds of the prescribed quantity of bone-ash are to be omitted, and an equal proportion of powdered tarras to be substituted : and if the sand be not of the coarsest sort, more tarras must be added, which should not exceed in weight, one-sixth part of the former. When a cement of the finest grain, and in a fluid form, is required, so that it may be applied with a brush, flint-powder, pounded quartz, or other hard, carthy substance, may be used, instead of sand, but in a smaller quantity, and in proportion to the fineness of the flint, or other powder, so that it shall not amount to more than six times, nor less than four times, the weight of the lime. According to the greater, or smaller quantity of lime, the cement will be moreorless liable to crack, by quick drying. Where the sand above described, cannot be conveniently procured, or, where it cannot be washed and sorted, that which bears the greatest resemblance to the mixture of coarse and fine" sand, may be selected; provided due attention be paid to the quan-tity of lime, which is to be increas-ed, when the sand is fine, and to be diminished, in proportion to its coarseness. In situations where sand cannot be procured, any durable stony body, or baked earth, grossly powdered, and sorted in a similar manner, may be substituted by measure, but not by weight, unless such gross powder be of the same specific gravity. - Sand may be cleansed from softer, lighter, and less durable matter, and from those particles which are too fine, by various methods, preferable in certain circumstances to that above described.

Water may be found naturally free from fixible gas, selenite, or clay; and may be employed in-stead of the cementing liquor; in which state, the water will not require so much lime for its pre-paration. Where stone-lime can-not be procured, chalk-lime, or shell-lime, which approaches near-est to stone-lime, may be substi-tuted, in the manner above direct-ed ; with this exception, however, that fourteen pounds and a half of chalk-lime will be necessary, instead of fourteen pounds of stone-lime. The proportion of lime may, without inconvenience, be increased, when the cement, or stucco, is to be applied, where it is not liable to dry quickly: on the contrary, it may be lessened, and the deficiency supplied, with considerable advantage, by causing an additional quantity of the cementing liquor to soak gradually into the work, so that the calcareous matter of this liquor, and the elastic fluid attracted from the atmosphere, may fill and strengthen the workmanship. The powder of almost eve-ry well-dried, or burnt, animal matter, may be substituted for bone-ash, and several earthy pow-ders, especially the micaceous, and the metallic, as well as the calca-reous ashes of mineral fuel, and the elixated ashes of various vege-tables, the earth of which cannot, by burning, be converted into lime, will, in some measure, answer the purposes of bone-ash : in short, the quantity of the latter may be less-ened, without injuring the cement, particularly in those circumstances-which admit of a diminution of lime, and where the cement is not liable to dry quickly. For inside work, it will be very useful to mix hair with the cement.

The Last patent, which we shall notice, was granted in November, 1800, to Mr. John Baptist Denize, chemist, for a cement, applicable to various purposes. The basis of this is petroleum, or rock oil, in any form; in which a small portion of sulphur is dissolved, by melting ; to which is added any kind of vitrescible, earthy matter, such as clinkers, and scoria, from iron, or glass furnaces; puzzolane, or any volcanic ashes, etc. These are to be powdered, and stirred into the melted sulphur-oil, till the whole becomes of such a consistence as to be easily spread with a trowel, and docs not adhere to the lingers, when cool. This cement is firm, durable, and impervious to moisture.

Those of our readers, who may be desirous of additional information, relative to this interesting subject, we refer to the translation of M. Loriot's " Practical Essay on Cement and Artificial Stone, " (8vo. Is. (6d. Cadell, 1774); and to Dr. Higgins's "Experiments and Observations, made with a view of Improving the Art of Composing and Applying Calca-reous cements, and of preparing Quick-Lime, etc. (8vo. 5s. Ca-dell, l780); in which the matter is fully and ingeniously discussed. See Mortar.

Cement. - In July, 1800, Mr. J. B. Denize obtained a patent for acea cement intended to serve as a substitute for putty, etc. - He conjointly employs metallic, earthy, carbonaceous, bituminous, and mucilaginous substances, together with desiccative oils. In preparing this compound, the hard matters are previously reduced to a fine powder, while those susceptible of a liquid form, are melted on the fire : the pulverized substances are then gradually added to the liquid, constantly agitating the whole, while under the action of heat. Thus prepared, the mass is exposed to cool and harden ; in which state it is kept for use. Before, however, the cement can be applied, it must be broken into small pieces, and liquified with a portion of tallow, or other unctuous matter: - according to Mr. D. it is perhaps more capable of intimate and powerful adhesion, than any other cement hitherto contrived. - A minute specification of this patent is published in the 16th vol. of the " Repertory of Arts, " etc.