July 23, 1908] 



NATURE 



283 



ing conditions, and may have been due to ancient wind- 

 action, or even to termite ants, whicli subsequently passed 

 away in the face of climatic changes. Some 250 pages 

 of the paper are devoted to the underground water-supply 

 of the region, and various methods of well-drilling are 

 described and illustrated. 



Bulletin No. 298 contains a record of deep wells drilled 

 during 1905, particulars of which are collected by the 

 Survey, while geological advice is freely given to well- 

 sinkers who ask for it, and the difficulties likely to be 

 encountered are pointed out. Bulletins Nos. 279, 286, 304, 

 317, and 318 (1906-7) deal with various coal and oil dis- 

 tricts. Indications of underground structure are given on 

 the maps, and in No. 318 transparent sheets with contours 

 are supplied, to be laid over the ordinary maps, and 

 indicating the depth at which a particular oil-bearing bed 

 may be encountered. No. 320, by Messrs. S. F. Emmons 

 and Irving (1907), contains important additions to what 

 has been previously published on the ores of LeadviUe, 

 Colorado ; the Downton district serves as the particular 

 instance. Waters originating during the cooling of 

 igneous masses are here put into a prominent place as 

 ore-bearers (p. 66), though at LeadviUe the concentration 

 of ore " in exceptionally rich bodies has come about 

 through the agency of surface 

 waters " (p. 72). Bulletin No. 297, 

 by Mr. M. R. Campbell (1906), treats 

 of another asset of Colorado, the 

 Yampa coalfield, north-west of Lead- 

 viUe, where the coals are in the Mon- 

 tana stage of the Upper Cretaceous 

 strata. Mountain-building processes 

 have converted much of this " sub- 

 bituminous " coal into coal of a 

 higher grade, while metamorphism by 

 igneous intrusions has given rise in 

 parts to anthracite. -Mr. Darton, in 

 the Bighorn memoir mentioned above, 

 describes coals, including a 7-fect 

 seam, still higher in the Cretaceous; 

 system to the north of Yampa. 



Bulletins No. 303 (S. Nevada, 

 1907) and No. 295 {Yukon-Tanana, 

 .Alaska, 1906) are concerned with 

 gold-mining ; the topographical map in 

 the latter is regarded as the most 

 important feature, and similar sheets 

 are being rapidly pushed forward on 

 the I : 250,000 scale. 



Petrographers and chemists will be 

 grateful to the Survey for Bulletin 

 No. 305 (1907), by Mr. W. F. Hille- 

 brand, on " The .\nalysls of Silicate 

 and Carbonate Rocks." This will 

 take the place of the well-known 

 No. 176. -Attention is given to the 

 question of porosity (p. 38), which is 

 so important a factor in building-ston 

 composed of carbonates are now for the first time specially 

 considered. Mr. T. N. Dale describes (No. 313, 1907) 

 the " Granites of Maine," the foundation of a very 

 important industry. The striking sheet-structure of granite 

 is discussed (p. 30), and stress is laid on its possible origin 

 by compressive strain. Dark knots in the granite due to 

 segregation are distinguished from the inclusions that 

 also occur (p. 50). Examples of the use of the granite in 

 carved work are shown in the illustrations. Messrs. 

 Emerson and Perry (Bulletin No. 311, 1907) describe the 

 " Green Schists and -Associated Granites and Porphyries 

 of Rhode Island." Interesting features of contact-meta- 

 morphism occur, including the brecciation of a micro- 

 granite by a later granite magma, and the production of 

 interstitial films of biotite and magnetite between some of 

 the closely adjacent fragments (p. 68). Explosive action 

 at the top of the dome seems to have blended this breccia 

 with a true Carboniferous conglomerate at the surface. 

 A new locality for riebeckite is here given (p. 53). 



The only palseontological bulletin received by us is 

 No. 292 (1906), by Mr. "R. S. Bassler, on " The Bryozoan 

 Fauna of the Rochester Shale." This shale is a member 



NO. 2021, VOL. 78] 



of the Niagaran series (Silurian, i.e. Upper Silurian), and 



is well displayed in the Niagara gorge. The conditions of 

 its deposition seem to have been admirably suited for 

 bryozoan life, and types abound which are not represented 

 conspicuously in contemporary -American strata elsewhere. 

 -As " compared with the Ordovician types, the noticeable 

 features are the predominance of the Cryptostomata and 

 the decline of the Trepostomata " (p. 2). The author 

 (p. 8) asks English workers to undertake a comparison of 

 the Rochester bryozoa with those which have " received 

 but little study " in the Buildwas beds of the Wenlock 

 series. The thirty-one e.xcellent plates in this bulletin will 

 prove helpful to anyone who will accept this friendly 

 challenge. Even our Carboniferous bryozoa have been 

 much neglected during the last quarter of a century. 



Before we pass to the surveys of separate States, we 

 must mention Mr. Weeks's continuation of the " Biblio- 

 graphy and Inde-K of N. -American Geology and 

 -Mineralogy " (Bulletin No. 301), which covers all work- 

 done from 1901-5 inclusive. 



The Wisconsin Geological and Natural History Survey 

 sends us three bound Bulletins. No. xv. is on the " Clays 

 of Wisconsin," by Dr. H. Ries (1906), and treats of the 

 characters of clays in general from an economic point of 



and the rocks 



Fig. 3. — Sheet-structure in granite, Sullivan, Maine. 



view, as well as giving details of those worked within 

 the State. Tests of clays and bricks have been made for 

 this report. On p. 213, in an appendi.x on " Molding 

 Sands," we note a formula for determining the pore-space 

 of a sand which would give far too low a result. 

 " Grains " should, we presume, read " grams " in this 

 passage, and we take it that the formula intended is 

 100 (Vii — W)/Vd, if a percentage is required. 



Bulletin No. xvi. is a volume of nearly 700 pages, with 

 folded maps,, by Mr. S. Weidman, on the "Geology of 

 North Central Wisconsin " (1907). About 75 per cent, of 

 the area is occupied by intrusive igneous rocks, which are 

 fully described, and which have sometimes been crushed 

 and converted into schists. The troctolites and nepheline- 

 syenites will attract petrographers, and there are interest- 

 ing intermixtures of granites and dioriles (Plates xxii. and 

 xxiii., for example), and gneissose " nepheline-peginatites, " 

 the banding in which is due to original flow. On p. 30S 

 the new variety of pyrochlore, called marignacite, is 

 described. The account of the glacial features of the area 

 is prefaced by a general sketch of North -American glacia- 

 tion, and the' full and admirably illustrated chapters on the 

 surface-configuration ought to interest every educated 



