lime, without improving the quality of the lime. In order to do this, he burnt it, and reduced it to powder. And thus he produced cements possessed of the necessary qualities of quickly drying, and a great tenacity. The author allows, indeed, that on account of carriage, this substance is rather costly; but he nevertheless thinks, that the great advantages which it produces, will well compensate for the expense of it.

M. Pasch made more than a hundred experiments on manganese, which has been so greatly recommended to be employed in the formation of hydraulic cements; he used it both in its natural and in its calcined state. It has been stated, that we could obtain a good cement from mixing pulverized lime, manganese, clay, and sand together, and well incorporating the mass. He thinks, that in this case, the good quality of the cement is due to the clay, and he could not perceive that any advantage was derived from the manganese, and therefore advises that it be omitted. Neither. could he find that much good was obtained from the use of trapp, grunstein, the powder of burnt granite, and ochre ;, nevertheless, he thinks that the last mentioned substance did a little contribute to the improvement of the cement.

With respect to the various kinds of lime, the author has found that they are all susceptible of being converted into hydraulic cements; but that the lime-stones of the alluvial formation (flodlægrige) produced a better lime than those belonging to the older formations. That a considerable. portion of argillaceous earth mixed with the lime caused. the cement to endure longer under water; that the siliceous earth gave the cement a greater degree of hardness, but did not prevent it from experiencing the effect of water upon it. He found that the bituminous calcareous stones were the best, on account of the portion of aluminous schistus which was contained in all those which the author assayed. The cements made with these kind of limestones became dry in a few minutes, and acquired the hardness of

VOL. IV.

N

stone; and he thought they might completely replace the famous Parker's 'cement.

It was proved, from the following chemical analysis, that the two cement stones contained very near the same sub

It is without doubt desirable, adds the author, to determine the exact proportions in which we should mix the different ingredients to form a good cement, but much depends upon the quality of the lime employed; and as the composition of the different kinds varies so much, so it is not possible to determine the proportions of the other ingredients. M. Pasch speaks of the lime from Faalhagen, which is procured from the lower strata, upon the border of the ocean, as having proved excellent in the works for the Goetha canal; this stone is of a reddish tint, and contains fifty per cent. of lime; the remainder being a siliceous earth mixed with the oxide of iron; and also a little argillaceous earth and oxide of manganese. After being burnt, the stone gave twenty per cent. of pure lime. This lime afforded an excellent cement when prepared in the following manner. Pulverized lime, not slacked, one part by measure; and sand, half a measure; or instead thereof, lime pulverized, and not slacked, four measures; sand, two measures; pulverized aluminous schistus, one measure. For the rest the author is unable to give a general formula for mixing the ingredients of a good cement, but he indicates, at least, the principles according to which the mix

ture should be made. Thus, when the sand and the alu minous schistus have been mixed in proper proportions, the quantity of lime to be added should be such, as that the hydrate of lime should fill all the interstices of the mixture. Before proceeding however to make a good mixture, it is necessary to know many particulars; for instance, the volume of hydrate of lime, which is obtained from a measure of pure lime; the degree of compactness afforded by: the sand, and the aluminous schistus to the mixture; and lastly, the capacity of the empty spaces which remain between the particles of sand, &c.

XXVII.-On the Swedish Iron Mines and Iron *.

THE office of the iron mines, in Sweden, is charged with a part of the administration of the mines, and other royalties. In the mines of other countries, there are but few kinds of minerals produced, and those are well known, so that it is easy to calculate with certainty the produce of their ores. In Sweden, on the contrary, the same mine yields many different minerals, and they every year open different beds and veins, from whence results the necessity of constantly making new assays, and this will account for the great number of analyses which are contained in the volume published by their school of mines; and thus, this eighth volume chiefly consists of the chemical analyses of minerals made by the pupils, and also of calculations of the proportions between the forms of their furnaces, the quantity of combustibles employed, and the results of the fusions.

It also contains an account of the experiments made by M. Uhr, to prove the strengh of bar-iron. He took the bars made at the iron-works of Skebo; these were three feet long, two inches wide, and three quarters of an inch in thickness, and each bar weighed 15.76 Swedish pounds.

* From the same work as the preceding article.

These were firmly fixed horizontally and edgeways, at one end, into a stout upright piece of timber; and to their other ends the scale of a balance was suspended and loaded with weights. The author gives a table, indicating the different weights required to bend the bars, and which varied from 59.19 Swedish lispunds, to 83.04. The quality of the ore from which it was produced, and of the iron in each bar, are also indicated; as likewise a figure is given of the machine employed for proving them,

Vol. IX., for the year 1825, part I. contains two reports by M. Uhr; on experiments made at the ironworks in Sweden, during the year 1824. These experiments call in question the accuracy of the former report upon these subjects, made by the pupils of the school of mines, concerning the relations which exist between the furnaces, the quantity of the combustibles employed, and the results of the fusions; and the author gives many tables, containing the results of his own experiments. The second report tends to expose the employment of cylindrical rollers, in the preparation of bar-iron, according to thy English method. Hitherto these cylinders have not been much used in the Swedish iron-works, on account of the great expense of the machinery; and it is probable that the Swedes will remain for a long time faithful to the employment of their ancient processes, of forging their iron into bars.

Vol. X., for the year 1826, part I. contains a long report from the mining engineers, with numerous calculations, on the construction of the tuyeres and chimnies of smelting-furnaces, on determining their height, their capacities and those of the bellows; and on carrying to a higher degree the fusing powers of charcoal. Another report by M. Uhr, on the commerce of the English in iron, with many tables, founded upon parliamentary documents.

Part II., which forms a volume of 600 pages, bears an especial title: Forsak at bestamme valsadt och schmidt staangjerns tœthet; or, " An Essay to determine the Den

sity, Ductility Malleability, Elasticity, and Strength of Bar-iron; both when passed through Cylinders, and made by the Forge." This work, so extensive, consists of a long series of experiments, which the Swedes were provoked to make, in consequence of the preference which obtains, in some countries, for the English rolled iron, over that made in the forges of Sweden; and it was certainly for the interest of this latter kingdom, to make great and numerous experiments upon the subjects. They promise to continue these reports.

Remarks. By the EDITOR.

The employment of cylindrical rollers in the English iron-works is chiefly valuable for the vast quantity of iron it enabled us to produce: and, no doubt, most excellent iron may be made by their agency. At the same time we must ever lament, that it enables the fraudulent manufacturer to imitate the appearance of the best iron; and it is only by the effects produced upon it in the forge, that the purchaser finds out the difference between good wrought iron, and that which is very little better than cast iron, squeezed by rolling into the form of wrought iron. Now the Swedes distinguish the various kinds. of their iron by particular stamps or marks, so that the purchaser can always be sure to have it of the quality he wishes, either for steel-making, or any other purpose; and the Swedish government have always made it a point to preserve the integrity of their marks.

The late Samuel Homfray, Esq., one of the greatest iron manufacturers in this country, had it greatly at heart to compel the makers of English iron to adopt a similar practice; and it had been well for this country had he been enabled to have carried his wishes into effect.