302 ANNUAL OP SCIENTIFIC DISCOVERY. 



sienite, and in tracing across the vein in a right line, magnetic action 

 was not perceptible for more than four feet. I repeated my experiments, 

 and found four feet three inches was the maximum distance that the 

 ore was found magnetic. I broke off fragments in a line across the 

 vein, at the distance of three inches from each other, and, after pulver- 

 izing, weighed one hundred grains from each parcel, and applied a com- 

 mon magnet to them . The magnet would take up all or nearly all of 

 the powder from such parts as came from the side of the vein nearest 

 the igneous rock, and gradually diminished as they receded from it. 

 I failed in establishing any regular series or ratio for the diminution 

 of magnetic action, but inferred from the results that the iron of the 

 Franklinite, in the parts of the vein in contact with sienite, was a pro- 

 toxide, while the mass of the vein was a peroxide ; and intermediate, 

 for the distance examined, as before stated, there was a mechanical 

 mixture of the two oxides. In presenting these facts, an important 

 geological question arises : Is the metamorphism of this metallic 

 vein attributable to the agency of the intrusive rocks in contact with 

 it ; and, if so, should we not infer that the igneous intrusive rock is 

 more recent than the vein of Franklinite 1 



COAL DEPOSITS OF IOWA AND OREGON. 



FROM the forthcoming report of Dr. D. D. Owen, U. S. Geologist, on 

 the geological survey of Iowa, Wisconsin and Minnesota, we derive the 

 following facts in regard to the coal formation in Iowa : 



" Between Johnson and Iowa counties, an uplift of carboniferous 

 sandstone is encountered, which is probably near the eastern limit of 

 the Des Moines coal-field. The Iowa river meanders near the eastern 

 margin of this coal-field, but the seams presented on the river are of 

 inferior quality. It is upward of two hundred miles in the direction 

 of the valley of the Des Moines across this great coal-field. West- 

 wardly it extends from Des Moines river nearly across the State of 

 Iowa, and includes a considerable portion of Missouri. The entire area 

 of this coal-field, in Iowa alone, cannot be less than 20,000 square 

 miles, in all, embracing a country nearly equal in extent to the State 

 of Indiana. Although of so great an area, this western coal-field is 

 comparatively shallow in Iowa, probably hardly exceeding fifty fathoms 

 in thickness. It consists of three well-marked divisions a lower cal- 

 careous, about one hundred feet thick ; a middle argillaceous, from 

 fifty to one hundred feet thick ; and an upper silecious, from eighty to 

 one hundred and twenty-five feet thick. The beds of coal at present 

 discovered are confined to the middle division, and are hence, probably, 

 not over one hundred feet in thickness." 



The district of country embraced in the surveys, made under the 

 superintendence of Dr. Owen, comprises about two hundred thousand 

 square miles, lying both east and west of the Mississippi, and occupies 

 an area six times as large as the State of New York. Ninety-one 

 streams have been explored, one fourth of which were navigated from 

 their mouths to their sources, in bark canoes. 



Coal in Oregon. Samples of bituminous coal, obtained nearPuget's 



