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Show ' " iheIeology of 1 ofnorth america Kl Educational Reference Work Ittued jt ' By The Geological L in ,j Survey Hj It Is now four years slnco tho Unl- H i ted States Gcologlcnl Survey publish H V ' ed as a help to teachers and students H ' of geography and physiography a pa- B " ' per by Professors Salisbury and At- Hu ' -wood, of tho University of Chicago, HI I on "Tho Interpretation of Topogra- Hfl " ' I phlc Maps." Tho demand for this H j f ' publication, which was strlctlyl cdu- H j; catlonal in character, was so great H that, notwithstanding two editions ' 1 wcro printed, even tho small allot- ft II' ment held for salo is now nearly ox- K jj 5 haustcd. Meanwhllo teachers of ge- K . ' jj' ograpby In nil grades In many parts H d' of the country have been receiving H I D( most practical nld In their work as H; J?4 tho Geological Survey lins Issued to- H 0 pographlc sheets covering tho areas W , r;; in tho vicinity of their schools. Tho H D( Survey has also recognized tho need H of professional men educationally in- Hi , , tcrcstcd In the different branches of H i)1 geology by tha publication of such H I works as Clnrko's "Data of Gcochcm- H y. istry," now In Its second edition, and H j papers on paleontology and glaclol- H ogy. H J3' I Tho Survey1 has now issued auoth- H V)! ' cr larg0 work wnlcn "'" ho ot cs" H J q pedal valuo to teachers and advanc- U D,1 ed students of geology. This work, H -TM which concerns geologists more than H' 2 ' gcographors and which is printed as H rj Professional Paper 71 of tho Survey 1 D ' Is entitled "Index to tho Stratlgra- M D ' phy of North America by Bailey Wil- H 5 I lis, accompanied by a geologic map 'j , I d of North America, compiled by the H J D United States Dcologlcal Survey in fljj t D co-operation with Geological Survey H 1 q of Canada and the Instltuto Geologl- H I jj co do Mexico, under the supervision mWf E of Bailey Willis nnd George W. mW ;l D Stose." Ah Its tltlo implies this H J E large volume, comprising nenrly 900 H g urges, Is n description of the strati- U Jj E graphic geology of Uio continent; It H I E i3 not In nny senso n textbook In gc- U ology. The author of this report, W jj j which Is comprehensive In Its scope M ' E I and naturally has been very dllllcult B E of preparation, is a geologist ot Inter- m p nntlonnl reputation, formerly chief W j- geologist of tho United States Geo- m E logical Survey and now temporarily H 0 engaged In tho organization of but- 9 voys for tho Govcrnmout of Argon- K I1 The preparation of this great work V! I required tho examination of a vast J ?; amount of geologic literature of all f j; sorts, published during more than a '4 E , score of years and covering Green- K land, Drltlsh America, Central Amer- H I; lea, and tho West Indies as well as H - United States. In Its accomplish- H e ment, and particularly In tho comptl- H E ntlon of tho map, Mr. Willis rccclv- H ed tho friendly co-operation of tho H 5I : Canadian nnd Mexican geological sur B "$ veys, as well as of the Stnto gcolog- BBf I ists of our own country. For tho HBm 1 , most part tho descriptions of tho sev- H eral regions or districts nro cither H j quoted from tho original authors or H f 1 presented in tho form of abstracts. D ' 1 Though tho work Is essentially a com HR ' pllatlon or combination of published H; i' i geologic knowledge of tho continent H1 ' it contains nlso much hitherto unpub- B llshcd information, contributed by HI .. j. tho author nnd his associates Tho now data concern principally the geology ge-ology of Mexico, Cuba, tho Western States, und Canada. On account of the long tlmo rcqulr-i rcqulr-i ed for tho elaboration of this great ' task, a preliminary separate edition of tho geoldglc mnp of tho continent wns published over a year ago. Tho ontlro edition of this map, though obtainable only by purchaso nnd at a relatively high price, was exhausted exhaus-ted before tho appcaranco of tbo explanatory ex-planatory text. An edition has been printed to" accompany tho toxt and tho whole is now obtainable gratis from tho Survey. For easy and slmplo reference from the mnp to tho toxt and vlco versa, tho map is divided, In accordance accor-dance with tho scheme adopted for tho standard international map ot tho world, Into rectangular areas forming for-ming horizontal zones or tiers and vortical rows, 4 degrees of latltudo in holght and 6 degrees of longltudo In width, ench cast west zone or tier being designated by a letter and each north-south row by a number. Tho mnp Is about C feet high by 5 feet wide, on a scale approximately SO miles to tho Inch. On It tho distribution dis-tribution of tho vnrlous rock systems or formations Is delineated and differentiated dif-ferentiated In colors, so far as practicable, prac-ticable, though tho scnlo does not generally permit tho representation in rndily visible dimension of geologic geolog-ic divisions whoso outcrop occupies strips less than 4 miles wide. Tho geology of some rcmoto areas Is so llttlo known that tho space on tho map Is either leit blank or colored for tho grand division to which It Is thought the roens probably belong. On tho other hand, tho scalo obviously obvious-ly does not permit tho representation of nearly all tho formations present In many regions of tho country where the strata are steeply tilted or tho geologic history has been worked out in detail. For these regions re-gions tho Inquirer for detailed or local lo-cal cartographic Information must consult the original publications cited and bibllogrnpblcally listed in tho text. So nlso thoso searching detailed detail-ed information regarding the mineral wealth of an area must go to tho original publications, In particular to tho works dealing In detail with tbo mineral resources of tho different parts of the continent, rather than with tho geologic hlBtory and structure. struc-ture. As already stated, this volume has been prepnred to meet tho urgent ur-gent needs of tho professional teacher teach-er and the ndvanced student In geology. |