This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1859 edition. Excerpt: ... CARBONATE. CHAPTER IV. THE CARBONATE ORES. "whatever theory of iron-ore-origination or iron-ore-metamorphosis we adopt, the fact is patent to theorists of every sort and to those who will not theorize upon the subject, that a great change comes over the aspect of the ore-world when we ascend the scale of rocks and ages and reach a comparatively later stage than that of the Cambrian and Silurian eras. No longer magnetic and specular iron veins present their enormoiis and unsteady wedges among granite hills, loaded with curious and brilliant minerals. No longer vast deposits of brown hematite beneath a covering of gravel-drift follow the outcrops of the older limestones. There come instead to view innumerable thin but wide extended sheets of protocarbonate of iron, alternating with slates surcharged with carbon and sulphur, and with flagstones full of vegetable stemcasts but almost destitute of higher types of life. This new form of iron meets us first in any great abundance at the beginning of the Devonian age, recurs at long intervals during its elapse, makes one of its most brilliant exhibits at the opening of the Coal era, through which it reigns supreme, reappears with the coal measures of the Middle Secondary or Triassic age, and finishes its mission in the tertiary strata underlapping the sea coast. The first important fact afforded by this series of phenomena is this: that the age of carbon opens in both forms, organic and chemical, at once. Plants and animals appear in abundance when carbonate of iron appears in workable layers. How far this is a coincidence based on a relation of cause and effect is not yet well made out. Some see a closer and more necessary dependence of the carbonation of the ore upon the carbon set free from...