Ores which contain titanium, according to universal experience in this country, give an iron inclining to the defect of red short, but possessing the highest degree of tenacity. Such are several of the ores of the northern part of New-Jersey, and of Orange County, New-York. Manganese in small quantities renders iron harder, but injures none of its good qualities. Many of our ores contain manganese, but when carefully manufactured the iron appears to contain but an insensible trace of this _metal_. Nickel unites with iron in all proportions, and gives a soft and tenacious alloy; no good property of the iron appears to be injured by it. United with steel it gives an alloy of excellent quality. Nickel is rare among the ores of iron that are not of meteoric origin. But native malleable iron is occasionally found in large masses alloyed with this metal, and its extrinsic source has been fully ascertained. The masses are sometimes of very great size; we have already expressed our opinion that the iron that first came into use was derived from this source, and had been employed for ages before the processes for preparing it from its more abundant ores were discovered. Cast iron is distinguished into two varieties, which are obviously distinct in character, the grey and the white; a mixture of the two forms that which is called mottled. It is generally believed, and usually stated in the books, that both of these are combinations of iron with carbon, and that their difference in appearance and quality grows out of the difference in the proportions in which the two substances exist; that the grey iron contains the greatest dose of carbon, and the white the least. There is, as will be seen, good reason to question the latter part of this statement. The grey iron requires the greatest degree of heat for its fusion, is more fluid when melted, is softest, best fitted for castings which require to be turned or filed, and for those that must be thin; the white iron is very hard and brittle; the greatest degree of strength and tenacity is due to the mixture, or mottled iron, and to that variety of mottled in which the grey rather predominates.