512 



NATURE 



[October 20, 19 10 



south-west. Thus the Cretaceous coals at Crazy Mountain, 

 Montana, are too thin to be mined, except for local use ; 

 but at Lewiston, Montana, the Lower Cretaceous coal from 

 the Kootenai formation is of great value, though high in 

 sulphur ; the Grand Mesa field in Colorado has an 

 estimated supply of 15,000,000,000 tons of Mesaverde coal, 

 of a calorific value of from 8000 to 13,600 thermal units. 



.\ second Bulletin (No. 380), " Contributions to Economic 

 Geology, 1908," deals with minerals except fuels. Mr. 

 C \V. Hayes has superintended the preparation of the 

 reports on the non-metals and iron ores, and Mr. W. 

 Lindgren those on the rest. The Bulletin consists of 

 twenty-five papers and numerous bibliographies. Some of 

 the reports are based upon only a few hours' or a day's 

 visit, but others are preliminary reports based upon a 

 longer study. J. S. Diller and G. F. Kay describe the 

 Grants Pass goldfield in Oregon, which is one of those 

 frequent and disappointing fields where the gold is very 

 widely distributed through innumerable small veins and 

 veinlets ; the absence of well-defined lodes is unfavourable 

 to profitable mining, until some clue be discovered to the 

 distribution of the richer patches. The ores are found in 

 association with greenstones and granodiorites intruded 

 into altered sediments. The placer deposits are widely 

 scattered, and are worUed by many small mines, employing 

 from three to five men each. Some of the placers are 

 Cretaceous shore deposits. 



Mr. F. L. Hess reports upon the tin, wolfram, and 

 tantalum deposits of South UaUuta. Tin is so scarce in 

 the Cnited States that much interest was excited by its 

 •discovery in pegmatite dykes traversing the Algonkian 

 schists at Harney Peak. -Assays showed the presence of up 

 to b per cent, of tin, and the Harney Peak Tin Company 

 was established to work tne deposits on a big scale. 

 Three million dollars of English money, in addition to some 

 -American, was spent in the venture, and Mr. Hess tells 

 us that the 5000 tons of ore put through the mill yielded 

 only o'25 per cent, of tin. The tin cost more than its 

 weight of gold. This failure is, perhaps, not surprising, as 

 pegmatite dykes have never been found to pay as tin ores 

 except on a small scale. The wolfram ores of the same 

 locality are known from the descriptions of Mr. J. D. 

 Irving, and though Mr. Hess does not altogether agree with 

 his theoretical conclusions, he remarks that Mr. Irving's 

 prediction as to the limited economic value of the deposits 

 has been fully justified. This wolfram ore is of some 

 interest, as it occurs as a replacement of dolomite and was 

 introduced by solutions rising along vertical fractures. 



Of the four papers in this Bulletin dealing with iron 

 ores, one of the most interesting is by Mr. E. C. Harder, 

 on the ores of the .Appalachian region in Virginia. Some 

 of the ores occur in the prc-Cambrian schists and crystal- 

 line rocks of the country at the eastern foot of the 

 Alleghany Mountains ; but the ores are not commercially 

 Important. They, however, include the interesting titani- 

 ferous magnetites of the Blue Ridge, which have been 

 formed as segregations in a basic syenite (unakite) ; and 

 the truly magmatic origin of these small bunches of ore is 

 shown by the many included specks of minerals belonging 

 to the enclosing rocks. The more important ores occur in 

 the Palaeozoic rocks of the Appalachian plateau, including 

 ■" brown ores " of three distinct origins. They are 

 " mountain ores " associated with Lower '>.'ambrian 

 quartzites, " valley ores " found in residual! material 

 formed from Cambri.an limestone, and the Oriskany ores, 

 which occur as replacements in the Silurian Lewistown 

 limestone. 



The manganese ores of the Cnited States have been 

 studied by Mr. Harder, who promises a special bulletin 

 upon them. The ores are widely distributed, but are not 

 much mined, since they usually occur in pockets of 

 not exceeding 25,000 tons, and cannot compete with the 

 imports. 



Among reports on the non-metallic minerals is a short 

 note on the mica deposits of southern Dakota, by Mr. 

 D. B. Sterrett. The mica is found in pegmatites, which 

 are sometimes intrusive dykes and sometimes veins due to 

 pneum.itoIytic action. The two types pass imperceptibly 

 into one another. The supply of sheet mica for lamps and 

 furnace doors exceeds the demand, and most of the mica 

 obtained is employed for the manufacture of electric 

 NO. 2138, VOL. 84] 



machinery. There is a short report by E. G. Woodrow on 

 the sulphur deposits near Thermopolis, Wyoming ; the 

 sulphur is deposited by hot springs, where the water comes 

 in contact with limestone. The sulphur is deposited as 

 crystals, and also as masses replacing the limestone. 



Mr. Matson contributes some notes on the clays of 

 Florida, and describes «9ie ball clays, which are usually 

 described as kaolin, as they are while burning, and can 

 be used for either porcelain or white earthenware. As they 

 are sedimentary, Mr. Matson seems unnecessarily doubtful 

 as to whether they can be included in kaolin. 



Bulletin No. 374 describes the mineral resources of the 

 Kotsina-Chitina region of Alaska, by \- . H. Moflfit and 

 .A G. Maddren. The name Chitina means " copper river," 

 and copper is the most promising mineral of the district, 

 though it has not yet been proved to occur in conditions 

 under which it can be profitably mined. The district also 

 contains some coal and alluvial gold, which has been 

 worked since 1902. The copper is mostly found in the 

 lower part of the Triassic Chitistone limestone, where it 

 rests on the Nikolai greenstone, a series of basaltic lava 

 flows, from which the copper is thought to have been 

 derived. 



The investigations on the general mineral resources of 

 -Alaska made in igoS are reported in Bulletin 379, in a 

 series of nineteen papers, edited by Mr. A. H. Brooks. 

 The mining industry as a whole suffered a decline in 

 output during that year owing to the diminished yield of 

 copper. Gold is still the main source of wealth, though 

 the yield fell slightly below that of 1906. Four-fifths of 

 the supply is alluvial, and the cost of working the placers 

 is so heavy that only the richest arc worked. The lode 

 mines, on the other hand, are low grade, the most im- 

 portant being those of the Alaska Treadwell group. Its 

 ore yields only 2'3 dollars of gold per ton, but, owing to 

 the large quantity and easy methods of mining, it can be 

 worked at a cost of one dollar a ton. In spite of local 

 predictions, dredges have already proved successful, and 

 their use must add greatly to the available mineral wealth 

 of the district. The most interesting placer deposits are 

 those at Nome, on the Seward Peninsula, where the famous 

 Third Beach, discovered in 1905, is still being worked. 

 -Alaskan shore placers are at present the most important 

 that are being worked anywhere for gold. The report by 

 -Moffit and I^nopf on the Nabesma-White River district 

 shows that the copper there occurs in Carboniferous basaltic 

 amygdaloids and in limestone along the contact with some 

 intrusive diorites ; but the fabulously rich copper deposits 

 reported have not yet been found. J. W. G. 



AIRSHIP FLIGHTS. 

 |70R some time public attention has been directed chiefly 

 ■*■ upon the records achieved by aeroplanes. Two air- 

 ship flights undertaken during the past few da}s 

 serve to illustrate what may be accomplished by dirigible 

 balloons. On October 15, at about 8 a.m., Mr. Waltfer 

 Wellman left -Atlantic City in his gigantic airship 

 America with the object of voyaging to Europe; and on 

 the following day the frameless airship Ckhncnt-Bayard 

 No. 2 travelled from Lamotte-Breuil by Compi^gne to 

 Wormwood Scrubbs — a distance of nearly 260 miles — in 

 six hours. 



The CUment-Bayard Xo. 2 is 251 feet long, and its 

 greatest diameter 44 feet 4 inches. The Times gives the 

 following particulars of the construction of this airship. 



Inside the bag there are two compensating air balloons 

 which can be filled separately. The car, 26 feet 3 inche;- 

 beneath the envelope, is 147 "feet 5 inches long. The stern 

 is provided with a keel to preserve stability. The metallic 

 framework is composed of triangular steel rafters, except 

 in the portion occupied by the motors, crew,- and 

 passengers, where they are quadrangular. -At the hind 

 extremity this framework takes a turn upwards to support 

 the equilibrator, a large triplane-like apparatus with eight 

 square compartments resembling the main cell of a \'oisin 

 .leroplane, controlling ascent and descent. The equili- 

 brator, comprising the rudder, composed of two mobile 

 planes on vertical axes at either end of the triplane, is 

 worked by an irreversible mechanism. There are two 

 propellers driven by two 120 horse-power Clement-Bayard 



