June 30, 1893.J 



SCIENCE. 



361 



In Vol. IT. of the reports Mr. Mason has given much valuable 

 information relative to the iron ores. In his introductory remarks 

 he discusses the forms in which iron occurs and the relative value 

 of the various ores. He then takes up the kinds found in Mis- 

 souri, describes their distribution, and examines in detail coarse 

 and fine specular ore, limonite, red hematite, carbonate, and bog 

 ores. In this discussion, various facts are brought out of interest 

 and value to geologists and students of physical geography. For 

 example, it is concluded that the strata lying about the Archaean 

 outcrops of the Ozark JUountains are of Cambrian age instead of 

 Lower Silurian, as they have been almost universally considered. 

 An excellent description is given of Iron Mountain, Pilot Knob, and 

 other large deposits of ore, and this is followed by an account of 

 the probable origin of the ore beds. The veins are regarded as 

 veins of infiltration, fissures occurring in the rocks having been 

 filled by the solvent action of percolating water through iron-bear- 

 ing porphyries. The changes produced in topography of pre- 

 Cambrian time by this action of water are briefly sketched as 

 follows : — 



"In the first place, whatever the origin of the porphyries, it is 

 allowable to imagine the porphyry region to have been, in pre- 

 Cambriau times, mountainous, or at least hilly. These hills and 

 valleys must have had cracks or fissures in the rocks as we find 

 them to-day. Naturally, erosion or weathering and denuding 

 agencies would begin at the highest points. The products of dis- 

 integration would wash from the higher to the lower points. 

 Iron dissolved from the decomposed rocks would, by means of 

 percolating waters, find its way to the fissures in the unweathered 

 rocks at a lower point. In these fissures it would be precipitated, 

 either chemically, by coming into contact with alkaline or other 

 reagents, or would, by slow absorption of oxygen, be made insol- 

 uble. This in time would fill the crevices and fissures in the 

 lower rocks with a substance much less susceptible to weathering 

 influences. The rock-mass thus cemented would, as a whole, also 

 tend to resist weathering more efl'ectually than the rock not thus 

 protected. Iron deposits filling fissures would not be formed at 

 the highest points, since solution would tend to carry it either 

 deeper into the hills or into the valleys below. The result of this 

 would inevitably be that the erosive agencies would be much 

 more effective on the elevated portions of the country than on the 

 lower. Gradually the hills would tend to reach the valley level ; 

 the valley country, being protected by iron dykes and veins, 

 would resist such erosion. The final result would be that in many 

 cases the hills would be changed to valleys and the valleys to 

 hills" (pp. 57-58). 



An interesting account of the Ozark uplift occupies one of the 

 chapters. The region generally goes by the name of the "Ozark 

 Mountains," but it is mountainous in name only. It is an ellipti- 

 cal, dome-shaped elevation, about 140 miles wide and about 200 

 miles long. Its greatest elevation is about 1,100 feet The aver- 

 age slope, to the southeast is a little more than one degree, while 

 to the northeast it is less. The region may be divided into (1) 

 plateau, (2) hilly or " mountainous," and (3) river bottoms. In 

 the plateau region the rivers have their origin. The surface is 

 mostly gently rolling, well-drained, and not steep enough to pre- 

 vent easy tillage. Following the streams down in either direction 

 the bluffs grow higher and higher, the streams more numerous, 

 and there is soon reached a country cut by deep canons, or gorges, 

 with steep-walled divides. This is the "mountainous" region, 

 but when one climbs to the summit of the divide, instead of a 

 commanding view, there appears to be a plain spread out on all 

 sides. The "mountain" crests are all at the same level. Float- 

 ing down the streams the bluffs and hills grow higher and higher, 

 but the fact is soon apparent that, instead of mountains and hills 

 having been thrust up, the plateau has been etched into relief by 

 the streams. The river bottoms begin in the mountain region, at 

 first of little value or extent, but gradually widening out to from 

 one-halt to two miles. Here the hills lose their sharp crests and 

 steep slopes, and the bottoms rise gradually by an easy slope to 

 the uplands. 



Throughout the region the streams are peculiar. In many 

 cases they spring directly from the foot of a tall cliff and begin at 

 once to cut their gorges. These grow deeper, the walls frequently 



rising, by a succession of precipices of from 50 to 100 feet, to a 

 height of 500 feet. The courses of the streams are very tortuous. 

 At one place the Osage River flows a distance of seventeen miles 

 when it can be intersected by crossing overland only a siugle 

 mile. A departure from a direct line of from three to seven miles 

 is not at all uncommon. The absence of bowlders is also noticeable ; 

 this being due to the fact that the masses of rock falling from the 

 cliffs are soluble limestone or friable sandstone, and both are 

 quickly removed. The streams are also of large size, yet water 

 courses on the surface generally have no water in them. At the 

 same time many rise to impassable floods in a few hours. In 

 May, 1892, the Current River rose 27 feet in about eight hours. 

 The floods subside as rapidly as they rise, the cause in both cases 

 being the character of the country. There is nothing to conserve 

 the water and it runs off as fast as it falls. 



Yet another feature of the region is in the large springs. One 

 of these, called Meramac Spring, is said to flow at the rate of 

 10,000 cubic feet per minute. Current River rises from a spring 

 of about equal size, and these are but two out of a large number. 

 These springs are, of course, only the outlets of underground 

 rivers. Sinking Creek flows for a long distance as a surface 

 stream. "A few miles from where it empties into Jack's Fork it 

 runs into a eul de sac, formed by a crescent-shaped mountain 500 

 or 600 feet in height. Just before reaching this mountain it sinks 

 from sight and reappears a mile away on the other side of the 

 mountain in the form of a large spring." Naturally, with a scant 

 coating of soil on the hills, the vegetation is not there luxuriant. 

 Twenty or thirty years ago the hills were reported to be bare, but 

 now they are covered with a thin growth of jack-oak, hickory, 

 cedar, and yellow pine. But the growth in the river bottoms, 

 where the soil is rich, is luxuriant, the trees being close together 

 and of gigantic height. Here are found sycamore, gum, elm, 

 water-maple, water-birch, ash, hickory, and numerous oaks. All 

 are so connected by a net- work of vines that it is nearly impossi- 

 ble to get between them. 



The age of various sandstones and limestones that have been 

 described in different Missouri reports has long been a vexed 

 question and one that has given all who have attacked it great 

 trouble. This question is taken up by Mr. Mason, and his con- 

 clusions may be summed up as follows: — 



The geological age of nearly all of the rocks of the Ozark uplift 

 is Cambrian, and the name "Ozark series," originally proposed 

 by Broadhead, is adopted for them. Sandstones alternate with 

 limestones, and these have been known as the first or saccharoidal, 

 second and third sandstones, and the first, second, third, and 

 fourth magnesian limestones. The saccharoidal sandstone has 

 been generally correlated with the Calciferous of New York, and 

 the St. Peter's of Minnesota and Wisconsin ; and the magnesian 

 limestones with the Lower Magnesian of the upper Mississippi 

 Valley. Mr. Mason does not believe the evidence sutBcient to 

 make more than one sandstone and one limestone formation. For 

 the first he proposes the name of Roubido^ue sandstone, and for 

 the second the name of Oasconade limestone. The outcrops of 

 both sandstone and limestone have been correlated by lithological 

 characters, but it is shown that the two rocks vary greatly. Sec- 

 tions taken along Current River for a distance of sixty miles and 

 along the Gasconade for forty-eight miles show so much variation 

 that it is impossible to trace the different sandstones or limestones 

 with any certainty. There is, however, a stratum which bears 

 fossils of the same general character over wide areas, and by its 

 aid the connection between the sandstone and limestone can be 

 traced. From the lists given it would appear that the affinities 

 are more nearly with the Cambrian than the Lower Silurian 

 epochs. The conclusions given will probably render a reconsid- 

 eration of the age of certain beds at Eikie's quarry, near Baraboo, 

 Wisconsin, necessary. These beds have been generally regarded 

 as Lower Magne.-^ian. They are probably more likely Potsdam. 

 We have not space to go further into details, but we commend the 

 volume to the consideration of geologists. 



The second of our titles treats of a vastly different subject. The 

 first part is taken up by a general discussion of mineral waters in 

 respect to their origin, composition, etc.; and the second, by far 

 the larger part, is devoted to a detailed account of the mineral 



