Having had a number of inquiries recently regarding cements for the roofs of buildings, we publish the following, being the substance of two specifications of patents for such compositions :— First.—This patent was granted to R. H, Smith, of Cincinnati, on the 20th of January, 1857. The object of this invention is to prepare a cement suitable for roofing and other purposes that will not require the aid of fire in its preparation, and which will expand and contract under atmospheric influences without rupturing, and which will also speedily lose the offensive smell of coal tar, which is part of its composition. It is formed by mixing the following ingredients in a cold state :— To 21 parts of coal tar add one part of in. dia-rubber dissolved in turpentine. To 28 parts of coal tar add one part of gum shellac dissolved in alcohol. To 21 parts of coaltar add one part of boiled linseed oil. To 28 parts of coal tar add one part of common molasses. These four solutions are prepared in separate vessels, each being well stirred until a thorough incorporation takes place. They are then left to stand for thirty-six hours, then all mixed together, and thoroughly incorporated, when, as a compound, it is ready to receive the substances employed as a drier. These are prepared as follows :— To six parts of pulverized quick lime add one part of pulverized gypsum. To 24 parts of pulverized quick lime add one part of litharge. To 30 parts of powder quick lime add one part of yellow ochre. Each of these dual parts is mixed together first, then the whole are thoroughly incorporated. To every four gallons of the former compound of tar, &c, one quart of this drying compound is added, and thoroughly stirred, when it is ready to put on a roof by spreading it in a thin layer, and pressing fine sand into it with a trowel or other instrument, or it may be put on with a brush like paint. The coal tar is employed to give this cement body, the india-rubber to give it elasticity, the shellac strength, the linseed oil to rs-pel moisture, and the molasses to act as a deodorizer. It is stated that in the course of two or three weeks after this cement is put on, the offensive smell of the coal tar is all gone, whereas, without the molasses, it will emit a disagreeable odor for about eighteen months, and this is a most serious objection to the use of such tar for roofing. The drier described is employed for the purpose of solidifying the cement. Neither of the foregoing ingredients when used by themselves, or when combined with each other, is claimed broadly, but " the ee-ment formed of the materials described, prepared in the manner and in the proportions set forth, to be made and applied to roofing, &c, without the aid of fire, and by which the offensive smell of coal tar is neutralized." Second.—This patent was issued to Charles R. Milks, of Detroit, Mich., March 3, 1857. The nature of this invention consists in a composition for roofing, containing about double the quantity of rubber heretofore used, and which from long experience in the business, Mr. Milks found necessary to prevent its cracking, he uses ingredients, which have before been used in such cements, but they are employed by him in greatly increased proportions. Take twenty gallons of naptha or coal tar and place it in a large kettle. To this are added two gallons of asphaltum, dissolved in purified spirits of turpentine at a moderate heat (the turpentine must be fully saturated with the asphaltum) ; two gallons of gum shellac varnish (shellac dissolved in alcohol) ; two gallons of rubber dissolved in turpentine, and one and a half gallons of boiled linBeed oil. These are then subjected to a moderate heat, and ten pounds of soapstone dust, five ?pounds of sugar of lead, and one peck of plas- ter of Paris are added and thoroughly incorporated by stirring, when the whole is fit for use. This patentee asserts that it is a wrong practice to employ cements for roofing purposes without heating all the ingredients. The asphaltum and an increased quantity of shellac are necessary to give the cement a compact character ; the rubber and linseed oil make it elastic, the soapstone gives it body, and is a non-conductor. This cement is stated to be durable, and not liable to crack. The claim is for this roofing cement, " made up of the ingredients, in the proportions, and in the manner set forth." In preparing the first cement, there is not the least necessity for mixing the drier ingredients in three separate parts first. They can all be mixed together at once, and answer as good a purpose. We also cannot see the least necessity for mixing the ingredients of the primary solution separately, before they are all incorporated together. If all be mixed together as in the second specification, under the influence of heat, they will be more perfectly united. Excepting the molasses employed in these cements, all the other ingredients have been previously used in cements. In our next number, we shall publish two other specifications of recent patents for roofing cements.