would settle the question. The small expense required in sepa rating the lead from the ore, renders a good mine of it one flf the most profitable. Hence the lead mines of Illinois, lowa', Wisconsin and Missouri, have contributed largely towards the settlement and development of those States, giving birth to cities, towns, railroads, steamboats, and new life to their com* merce and agriculture. We should have remarked, when treating of the calciferous rocks of San Saba and Llane, that when in the latter county we were shown specimens of the sulphuret of lead, by one of the .settlers in that region, but the person who had them did not seem disposed to reveal the precise locality in which they were found, excepting that it was in Llano comity. In ISo'l, the Hon. W. P. Saufley (Senator from Davis, Bowie and Marion counties) took some specimens of iron ore from Marion county, in the north-eastern part of the State, to New Orleans and Montgomery, in Alabama, which were tested by chemists in both these places, and said by them to yield from 70 to 75 per cent of met die iron, and to be equal to the best Swedish iron. This ore was worked at the iron works of Mr. Nash, about one mile from Cypress Bayou, a navigable stream in Marion county, during the late war. In Davis county there are two tounderies near Sulphur river, a tributary of the lied River. These iron ores are in a timber region where there are forests of pine and other trees. Coal also occurs in beds, which crop out along-the Sulphur river, in both Davis and Bowie counties. We are indebted to Col. Saufie.y for this information with regard to the iron ores and mineral coal of that section. Petroleum is a mineral oil derived from the decomposition of organic matter, principally in a vegetable form, being mostly made by chemical changes in vegetable matter, beneath the sur face of the earth. It has been found in the rocks of nearly every geological age above the Azoic, but only in large quantities iio<tr, or at no great distance from extensive deposits of coal or lignice, both of which are. as we have before remarked, of undoubted vegetable origin. Underheatand pressure it is generated and made in coal beds, from whence it may run in streams through the crevices of the rocky strata below, or be there held in reservoirs until "struck" by the auger of some fortunate company or indi vidual boring through the rocks above. We can now see why in the oil regions some wells cease to flow. The reservoir may have become exhausted, or the oil stream may have been struck still higher up the stream or valley by the sinking of one or more wells.