November 29, 1901.] 



SCIENCE. 



851 



and others that the maples, lindens and button- 

 woods in Union Square, Washington Square and 

 Madison Square are now covered with fresh 

 leaves as in May, owing to defoliation by cater- 

 pillars ; that the catalpas, honey locusts and 

 poplars were but little eaten, and are not, there- 

 fore, covered with fresh leaves, but were injured 

 by an early drought, and have sent out new 

 shoots to replace those lost ; these new shoots 

 are now covered with fresh young leaves. The 

 English elms in Washington Square were little 

 eaten and have no new leaves. Horse-chest- 

 nuts have new shoots and some have new 

 blossoms. Cherry trees have also been in bloom 

 again. The magnolias and tulip trees of Bronx 

 Park have blossomed and fruited twice this 

 year. Edward S. Burgess, 



Secretary. 



THE SCIENCE CLUB OF THE UNIVERSITY OF 

 WISCONSIN. 



The first meeting of the Science Club of the 

 University of Wisconsin for the present college 

 year was held on Thursday evening, October 31. 

 The newly elected oflBcers of the Club are : 

 President, Professor W. W. Daniells ; Vice- 

 President, Professor Wm. H. Hobbs, Secretary 

 and Treasurer, Professor L. S. Smith. 



Two papers of both scientific and economic 

 interest were presented, the first by Dr. C. K. 

 Leith, on the ' Mesabi Iron Range of Minne- 

 sota,' and the second, by Professor C. R. Van 

 Hise, on ' The World's Past, Present and Fu- 

 ture Supply of Ores.' 



Dr. Leith's paper was based on a mono- 

 graphic report on the Mesabi iron-bearing dis- 

 trict of Minnesota which he is preparing for the 

 U. S. Geological Survey. He sketched the 

 marvelous development of the range frorji the 

 time of its discovery ten years ago to its pres- 

 ent position as the greatest iron range in the 

 world. The range exhibits Archean, Lower 

 Huronian and Upper Huronian rocks in typical 

 development, and with relations so clear as to 

 make the Mesabi almost a type district for 

 these three pre-Cambrian series. The iron ores 

 are confined to the 'iron formation,' which 

 forms the middle horizon of the nearly flat- 

 lying Upper Huronian series. The iron forma- 

 tion consists of ferruginous cherts, ferruginous 



slates and iron ore, all of which give evidence 

 of having resulted from the alteration of a rock 

 made up of gi*een ferrous silicate granules. The 

 granules contain fifty per cent, silica and thirty 

 per cent, ferrous iron, with little or no potash. 

 They were called glauconite by Spurr, but their 

 study by the U. S. Geological Survey shows them 

 not to be glauconite of organic origin, but a fer- 

 rous silicate deposited on the sea-bottom through 

 chemical reactions. The iron ores have re- 

 sulted from the alteration of this type of rock 

 through the agency of underground waters. 

 The ores are now found where the action of 

 these waters has been vigorous. These places 

 are the southward-pitching troughs of the 

 gently folded iron formation, and in the parts 

 of the troughs lying along the middle slopes. 

 The bottoms of the troughs are mainly slaty 

 layers within the iron formation itself. 



The iron-ore deposits of the Mesabi are sim- 

 ilar to those of other ranges of Lake Superior 

 in having resulted from the alteration of some 

 earlier rock, in having been concentrated by 

 underground water, and in occurring in troughs 

 with impervious basements. However, in the 

 Mesabi the rock from which the iron ores re- 

 sulted is the green ferrous silicate, while in the 

 other districts it is iron carbonate. In the Me- 

 sabi the pitching troughs containing the iron- 

 ore deposits have very gentle dips and great hori- 

 zontal dimensions, while the pitching troughs 

 in the other ranges are narrow and sharp, and 

 have great vertical dimensions. Finally, and 

 possibly in some way connected with these fea- 

 tures, in the Mesabi district the ores are ex- 

 ceedingly soft and friable, while the old range 

 ores are fairly hard. 



Dr. Leith illustrated the various methods of 

 mining the Mesabi ores, the most striking of 

 which is loading by steam shovels directly on 

 to cars. He described also the great mines of 

 the district, several of which are shipping over 

 1,000,000 tons of ore a year. 



The amount of ore in sight on the Mesabi is 

 roughly estimated at 500,000,000 tons, or about 

 twice as much as there is in sight on all the 

 rest of the Lake Superior langes together. It 

 is also far in excess of all the ore now known in 

 other parts of the United States. The develop- 

 ment of the Mesabi range has lowered the 



