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Un des symboles suivants apparattra sur la dernidre image de cheque microfiche, selon Ie cas: Ie symbole — ► signifie "A SUIVRE ", Ie symbols V signifie "FIN". tVlaps, plates, charts, etc., may be filmed at different reduction ratios. Those too large to be entirely included in one exposure are filmed beginning in the upper left hand corner, left to right and top to bottom, as many frames as required. The following diagrams illustrate the method: Les cartes, planches, tableaux, etc., peuvent dtre fiim^s d des taux de reduction diffdrents. Lorsque Ie docuniloi!;ists one of the most iMterestiiii>: distriets of tlie I'nited States, eiuhraeiiio; as it does, in u limited area, old crvstalline roeks, toijether with forms that are almost in their oriirinal condition of a beaeh sand and mud. In this reti'iou was tirst cstaldished the V)ase of the gieolosrieal eolumn, the Azoic ("• with- out Hie") System of Foster anii]ier in the Taheozoic or Eozoic of tills district, which iornis one of the most imi)ort- ant miniiiii; rea'ions in America. The jjeoloyy of this section is so dilHcult and comidicated that, in it.s tjeiu'ral discussion, |K'rliai)s no proposition can he stated concerninir any i>ortion of it to which exceplions cannot lie taken. Indeed, out of the general discussion «»f dillerent points comes in time the truth, and various geologists, even now, are working over this region in the emleavor to arrive at some consensus, or at h'ast to determine upon what points they can agree, and upon what points difference of o[>inion will have to exist between them at present, until further evideiu-e can he obtained. The writer will endeavor to give in a brief form that which appears to him at present to he the most correct statement of the geological structure of the region, admitting that from time to time, as more comi>lete evidence shall be ob- tained, he exjiects to change his views in the future, as he has done in the past, if that evidence shall cause him to believe that he has been mistaken.. ........,•• Z ORIGIN AND MODE OF OCCURRENCE OF COPPER-DEPOSITS. The rocks south of T ikc Superior have been formed in three ways : 1st, bv mechanieal means ; 2(1, by eruptive, igneous, or volcanic agencies; 3cl, by chemical action. Fragmental or Detrital Rocks. The mechanical agencies of the Azoic time acted upon some prior-ft)rnied rocks in like manner as we see rain, winds, Avaves, frosts, etc., now breaking down the rocks of the present day, causing them to be deposited as soil, mud, sand and shingle, forming detrital or sedimentary deposits. Such detritus one can see upon the shores of any lake or sea, being in many localities variable in its composition, and oftentimes abruptly clianging from tine mud to sand, or even to coarse shingle. At other localities upon the same lake shore one may observe a nearly nniform sand, mud or shingle stretching away as far as the eye can reach along that shore. Like uniformity and like abrupt changes are seen by the geologist in the rocks formed fron. the ancient muds, sands and shingle of the early seas and lakes. These deposits may have remained on the surface of the ancient beach, or may have been deeply buried under succeeding de- posits; but whatever may luive ])een their position relatixe to the earth's surface, they have been greatly changed or altt-red from tiieir original condition, although the evidences of that original condition remain plainly visible to him who has learned to read the worn, torn and worm-eaten book of Nature. In truth it may be said that no event can take place without leav- ing its effects behind, and these can be interpreted with greater or less clearness until their record has been entirely obliter- ated. To return : we find that these old muds, sands and shirigle have been acted upon, and metamorphosed or altered, l)y heat from the earth's molten interior, or from contact with igneous or volcanic rocks, with their accompanying hot waters. Or, again, these deposits have been affected by hot or cold waters percolating through them, bearing nuiterials which chemically act upon them; or, again, they may have been subjected to greater or less s<]ueezing and pressure during the fornnition of the numerous wrinkles that old Mother Earth now wears upon her rugged face, deeply furro^yed Uyj Iwr- tears. • *'••■«•• • .• • • • •• • .». • •• •••*•«• • ORIGIN AND MODE OF OCCURRENCE OF COPPER-DEPOSITS. Of all the au^onts of conflolidation and change in rocks, the chemically active waters are, to my mind, the most potent ; and it a|>i>ear8 to me probahle that dry heat and pressnre alone wonld be unable to produce any general and wide-spread rock alteration if it were not for the intervention of the jjcrcolating waters found in all rocks, so far as man has been able to pene- trate the earth. These waters convey the heat and other chemi- cal] v active agencies to the places where thev can act. AEeta- morphosed or altered detritus forms the oldest known rocks of the ]jake Superior district ; and we know of the original rocks onl}' by the remains of that deliris now found in them. From the character of that drbris it appears that here the original rocks were of igneous or volcanic origin ; that is, they made up the early-formed crust of the earth, or else were produced by the earth's primitive volcanic activity. When the muds, sands or shingle have been consolidated, they are found to form rocks that differ not only in the fine- ness of the material in them, and in their chemical and mineral composition, but also according to the ditferent agencies and conditions to which thev have been subjected. Thus it is that the muds have formed the rocks known as the argillites, shales, most schists, and some gneisses; the sands havi' Ibrmed sandstones, (piartziti's, some schists, and most gneisst's; while the shingle gtMieraily finds its expression in the conglomerates. The term argillite is used to indicate those consolidated muds that were largely composed of clay or argillaceous mate- rial ; but tlie argillites are commonly known as slates — a term properly applied to an argillite only when it has been subjccred to pressure and chemical action to such an extent that it has the ]iroperty of splitting indefinitely into thin plates that have no ri'lation to the original structural or sedimentary ]>]anes of the rock. Tliis pro[terty of being cleaved or split is known as cleavage, and it is by no means confined to that variety of argil- lite known as slate. AVhen (juartz sands form a sandstone which subsequently has bi'cn greatly altered or indurated, so that the rock is composed of a very hard, compact mass of quart/ grains, this variety of sandstone is known as quartzite. The terms schist and ii'neiss are used to designate all those ORIGIN ANIJ MODE OF OCCUIIUENCE OF COPPER-DEl'OSITS. nltored or iiR'tiimoridioscd (U'trit:il (lop(>sits whoso niiiu'rals are jin'imm'cd in more or li'ss parallel bands, alony; which the min- erals tend to lie flatwise or lena'thwise, causiiiij the rock to split into more or less rei>:nlar plates parallel to these hands. These hands (or foliation of the rock) may or nniy not he coincident with the oriiriiial jdanes or lines aloni; which the detritus was dei)osited (planes of sedimentation), and in the majo'/ity of cases in the Lake Superior rcijion do not so coincide. A strik- int:: example of this i-an he seen in the schist north of Ti-al Lake, where the idanes of dei>osition run ai'tiroximatt'lv north- 1' I'l' east and southwest, whih' tlu' foliation runs east and west. The varieties of schist are named according; to some one or more of the prominent nunci-als in them, as horid)lciide-schist, mica-schist, (jnartz-schist, chlorite-M-hist, aetinolite-schist, I'tc., for the schists that contain the minerals hornhlende, mica, quai'tz, chlorite, actinolitc, etc. The alteri'd muds, sands or shinu'les may he found continu- ous over laru'e areas; oi- they may he found, like their modern representatives, to i)a-- iiradually or ahrni>tly into one another. Thus it is, that a (luartzite is found to pass into (piai'tz-, mica- and ehlorite-schists; chlorite-schist into aru-illite-, couii'lomcrate- and hori Mende schists, etc. KuiTTIVE, A'oI.CAXIC OR LiXEOUS TiOCKS. To ohtain a fair idea of rocks of this character it is neces- sary to do as we have done with the detrital or iVau'mcntal roek>; ; that is, to observe carefully the recent forms and trace out their structure and various modifications and alterations. If this is done, we see that the erui»tive rocks are chan^'ed or metamorj)hoscd not less, and often more, than the sedimentary formations. This may he illustrated hy allowing:; some of the molten iron from our furmices to rim at wasti' ovi'r the <,^round and into the crevices, so as to he left exposed to the air, frost, wiiul and snow. It woidd first solidify, then crack or form Joints, as all rocks do, and, owin^ to the action of the air and rain, it would decompose and alter until finally it would form an t-arthy iron- ore totally unlike the ori^'inal iron. AV'hy is this V The answer is that the iron, when it passes from its furnace, is exposed in the outside atmosphere to conditions entirely unlike those in H ORIGIN AND MODK OF Of'CURRKNCK OF COPPER-DEPOSITS. 5 roil tlic iind all nld Oll- iv Cl- in in the riiniiu r, iiiul it imist cjiiiiiiji' its stiitc to coiitbriii with tliose chanjifd coiiditions. So, too, tin- t-niptivi' rodcs, coiniiii;' in a rK|ui(l state iVoiii tlu' inti'i'ior of tlic earth's t'uniaee, eaniiot endure nnehanii'ed the conditions whii'li exist at or near the earth's surface. They are in an unstahle condition, and must he made ovi'r into a more stahle mineral composition. The aii'encies that [U'oduce that chaiiiiv apjiear in ^i;H'neral to ]»e the same as those which alter the sedinientai'V formations, namelv, licrcolatinii" waters chemicallv active, |»ressure, and heat or cold. The lirst stat!-e is the chanii'e from a Tninid or pasty mass into a s(did one: latei- there comes a mori' or less variahle alteration that extends throuiihout the entire mass, and causes variation in the mineral composition and structure — set mueh .«() that at tinu's no trace of its oriu'inal condition remains, uidess it he its form or its relative position to other rocks. Tt is in conse([uence of these chanu'cs that rocks wliich wi-re oriu'iiudly peridotites or olivine rocks are now called serpen- tines, actiiiiilite-schists, talc-schists, dolomites and 'V /vA -'////'''/'">'.' and that fornu'rly moltiMi hasalts an- now desiiynated melaphyrs, diahases, n-althros, dioi'ltes, I'cloii'ites, ainphiholites, hornhlenW. Sw: Sot. IllM., 1^77, XIX., 2l7-l!;]7, Sdl) -.'iKl ; ]SS(», XXL, OMO;^ ■J-i;^-274, 288-2i>J; '^s.s, XXll., 41-.'-I32, 48r)-48!» ; 1.SS4, XXIII., 1U7--211 ; Mem. J/»,s. I'miip. Zoo/., 1.SS4, XI., 208 pp.; Am. Jour. Sci., 1H84 (3) XVIII., '.M-104; Sciaic', 1883, I., J27-130, 541; 18»4, III., 480,487; IV, 111 ; /)'((//. Minn. Coil. Siirmj, No. 2, lu'.l pji.; lirport of >^Hitc Buard of GcuL Sun, Mich., 189:1, IW pp. ORTdlN AND MODE OF OCCl'RRENCE OF COPPER-DEPOSITS. The striu'turc of cruptivo rocks (lifU'rrf very imicli iiccordini; to tlic'ir ('oinpositioii, and accortliiii!; to the conditions under wliii'li tlicy liavo cooled, wlietlicr slowly or rajildly, as widl as nccordin<; to the conditions to which they have hi-en snltjected. That is, a mass slowly cooling will he found to contain much lari>;er mineral forms, known as crystals, than a mass suddeidy clii lied. Tl le ( rujitivi roc m tl leir ri hit ions to tl 101 r associ iited country-rocks, will also vary aecordini; to the conditions in which they have reached their present position relative to the latter. If the ru|uid material (lava) forces its way throuii'h a rock, tillinc; the cracks that then existed in it, like putty fillinu- a crack in irlass, the solidified lava is known as a dike. Tt is to he ohserved, however, that when rocks are hut little consoli- dated, the orui)tive or li(]uid material tends to force itself aloiiii; the planes of deposition of the sedinu'iits, or parallel with the foliation, or else to hreak irrcijularlv throuirh whatever iwrtion of the rocks otters the least resistance. l\nt when the rocks have hecome solid then the tlow more commonly takes place alono^ cracks or iissuivs in the rocks, which extend across the country, like the cracks made in a thin sheet of ice. I'sually these dikes may he distin_i;uislied hy their heinir closi-ly wi'lded on each side to the country-rock, which is often indurated or hardened at tlie point of contact; hy their hein<; compact and tine-sjf rained at the junction with the country-rock, thus show- iiiii' a rapid coorinii', due to their comiiiir iu contact with ti.e cold sides of the tissure; also hy their heiiiij more coarsely crystalline or coarse-irrained toward the center than at the mar)i'('te(i. iitain miU'Ji '« sudclc'iily nssociatod iiditioiis ill 'ive to the rli a rock-, ■,V filliiiu- ii ■ Tt is to It' consoli- solf aloiici; I with tlio (T jiortioii tlie rooks l-ments thereof; also hy its coiit'ormity to the oriifinal surface of that undi'rlyin<; country-rock. Tho flow is usiuilly fine-ii-rainod or compact at its hase, owiny to rajiid cooliiiir; hut a short distance *Vom its liase it presents a coai'si'r texture, and usually shows tho coarsest structure helow tin- conti-r of the How, at a point which was tho louijest in cooliiiLC. The upptu' surface of tho flow is commonly wriid-cled, ci'liuliU' and slai::,i::y, if it has not heeii worn off, Tho overlyint; country-rock is laid down upon this surface; it con- forms [(t the ine(|iialitii's of the uiuh'rlyinij lava, and li'cnerally contains iVaicmonts (h'rived from it. Tho overlviiiii; sediment- ary rock is not welded to tho underlyini!; hiva, nor does one afloct the otlur in any way, unless it he hy chomical action. AVheii any explosivt' action has takt'U jthico, ashes and larijor fra^jnieiits of flu' disru[»ted lava are stri'wn ahout, which may or may not he suhse(|Ui'ntly worked over hy wind and water. Lava, as soon as it is exposed to the waves, is worn away, like any otiier rock, and wo find its worn detritus deposited hy its side, ire tiu' main nuiss has h-ecn cooled. CiiKMicALLv Deposited Materials. Every kind of chomical deposit, even sul)limation-doposits, can lie considered as resultiuii; frt/Ui the solution of mineral matter throuu-h the agency of the chemically active percolating or surroumling waters, which remove suhstancos from one htcality to another, or replace one material hy another. While H uHKilN AND MOliK OK (n.< I UUKNCK OF ColM'KK-Kin'UrilTS. it is not alwiiyn tnic, it is a ii-i'iu'ral niK' llial ori'-dcposits nvv most foiiiiiioiilv IoiiikI ill n-ijioiis of cniptivc ro<'lntiiiii«> its iiii occur, iliC SillDO source ()(' "s siirljicf 'ortioii ot' l- I'lVSOllt ior oC the iiistaiici's iist. prior iiiiilitioiis li'ccssit V, oil tlicir is iiiittii- lu'ir piis- iiiiiitioiis cuts, iis Sllcll ilS licy will CXjKtScd <»M till- ciirtli's surt'iicc, and this h'ads to dcu'iinhition, dissipation and losH of ciicruT on Ihi'ir |tart. in other words, the rocks lend to pass I'loiii an nnstahlc towards a more stahle stale. Tile rapidity ot" these chaiiu'es (hpi'iids not only upon the (.•iu-niical constitution ol' the rocks, hut also upon the special circ'UiiistaiK'cs in which they are placed. In the ha>ic rocks, lu* thoso eontaininu^ much iron, inau'iicsiitin, calcium, aluminum, et<'., the alterations are comparatively rapid, hut in the acidic rocks much slower. If rocks of eruptive origin are stinru'd umhr the microscope, these alti'rati(»ns vn\\ he readily ti'aced from their earliest to their latest statues, and are usually found to he ill a ratio to the au'»'s of the rocks or to the particular in- iluelices to which they liav<' hei'li rcspectiscly silhicctcfl. Jt is these idti-ratioiis that ha\'e led to the iniiltiplicity of rock-names, and to tin,' confusion of nomenclature ; litholoiiists and uH'oloii'ists, as a rule, formerly su[»posiim' that as a rock then was, so it always had heeii and always woiihl he. l''or exam- ple, the la\a Hows of Keweciiaw Point, which were once identi- cal wiih the modern hasalt.ic lavas of Mt. Mina and of K'ilaiiea, are now di -i^-jiated, on account ol' their alleraraui and aii'c, as melaph\rs, diahases, diorites, etc.; aiidesite in its channvd ii'uisc is thsiu'iiated as pro|iyliU', diahasc-porphyriU', jioi phyrite, diorite, etc. ; rhyolite as I'elsite, ipiail/.-porphyry. pi'trosilex, or- thofclsite, etc. ; |)eridotites, or olivine I'ocks, as serpentine, talc- schi>l, etc. The propylite of the ("oiiistock Lode, Ne\ada. is a strikiiiix e.xample. The present writer was the first to call attention to the fad lliat the foitieih paralh'i propylite> Were allere(l forms of pre-teiliary and tertiary andesitcs.'- The [lositioii then takt'ii has heeii fully coiilirnied hy hr. (J. I'\ l)ecker,j and \>y his col- lea^'iie, ^Vriiold ilai^ue. I>r. lU'cker further states that I'Very decomposed rock in the district has hi'eii taken for propylite. 'I'he ahovi' mentioned chaiines, or alterations, in rocl;s of the same conipositioii appear to he laru'ely depi'iidi'iit upon tiie ac- tion of inlillratiiin' watiu's, and their ra[)idity seems in a laiio to the temperature of llu' waters or to the soKeiits eoiilaiiU'd therein. 'J'hese alterations appear to consist, in si^'Ueral, of inoleculai' transferences or clu'inii'al reactions in the rtick-mass * /.''(//, Mas. Cnwp. /o„l., iSTi), vol. v., ini. '281,28"), L'SC. f "Cii'uli){;v of tile I'lHiistock i.oile and W'asliuo Districts,"' 1>'82, pi). 12-1.50. 10 ORIGIN AND MODE OF OCCURRENCE OF COPPER-DEPOSITS. as awhol(',;in(l are not contliicMl to special minerals; hence has resulted the lailure of theories of mineral pseudomorphism to explain roek-metamorphism, or alteration — the pseudomorphie eliaii<::es in the rock nniss heini; hut the resultiny; accident of the greater and more fi;eneral metamorphosis. In the process of alteration the orii^inal <;lass of the rock is broken np, form- ing various minerals according to its composition, while the oriirinal crystallized minerals are chanijed to a jjcreater or less degree, the resulting minerals being (pnirtz, various ores, anhy- drous and hydrous silicates, carbonates, etc. In the course of these changes there is everywhere seen a tendency to localize these se 'ondary products, especially the ores, which results in the removal of material of one kind and the deposition of an- otlier in its place, or in the tilling of fissures and cavities in the rocks. It is not uncommon to iind in rocks minute veins that under tlic- iniicroscope show variatior. in their tilling as they ])ass through difi'erent miner-ds. AV^hat has now l)een described as taking place in one rock takes place in all, and fre(|uently with various interchanges and reacti(M)s lietween the different associ- ated roi'ks. If we vtass gradually from alterations seen in the rock, and from the minute fissures ol)servellow that all ore-deposits not eruptive are, as ri'gards the t'arth, superficial phenomena and dei)i'ndent on its extiTiial agt'iieies, although they may be deep enough so far as man is cont'crned. Again, tew of these ore-di'posits would be expected, except in regions in which percolating waters and their attendant nK'tanit)rphism have l)eeii ellieient agents;''' while the various forms of ore-deposits would Ite associated with, and grade into, oiie another. 1 f we start, as all geologists do, with the belief ill an originally hot iluid globe, all roeks must have been derived, primarily, from Iluid material, wliieh contained all the elements of the iiu'tals or ores. The detrital rocd-pro(|- uct, is always a secondary, or alti'i'ation-]>ro(luct. Ibn'idilcnde in the recent andesites is foreign, luit in the older andesites, and ill almost all the older I'ocks of I'very kind, it is either a secondary prou'.'el or is a mor»' or less altered mineral. The mii'as, feldspars and . 2.J-2'J. ! [TS. ordance iidilj bo irongli- procipi- oc'ks by iiii? the y.sis of ssiirv to If" the 10 iiiiii- — iiidig- liiss, or •:i()iis : , wbat- .U'llKMlts "Ofk. i>V two, Ibistra- ■al, l)nt istie of '-|ir(Ml- I'lriidc! Vsitcs, fber a The s and iiiod- s •iiid 11 hv- iltcra- iiiiu- •1, pp. ORIGIN AND MODE OF OCCURRENCE OF COPPER-DEPOSITS. 13 orals can bo readily dislii)«i;uished I'roia one another under the niierosciipe by the eharaetors of tho minerals and their rela- tions to the roek-niass. Further, it may be [lointed out that olivine, except in tho more reeent rocks, is found, as a rule, to be more or less altered to, or replaced by, serpentine, (pnirtz, iron-ore, carbonates, etc. ; au^"ito by horn!)londo, biotite, chlorite, etc., and feldspar I)}' fpuirtz, kaolin, micaceous and cbloritic minerals, etc. These ehanii'es are so common that it is rare to tind in tho older rocks oriu'inal minerals that remain unchanu'od. Again, almost every mineral in rocks is found to contain in- clusions of other minerals, of glass, lirpiid and gases, thus viti- ating conclusions drawn from chemical analysis of the mineral. Since f)re-deposits are, in general, associated with altered or metamor[>hosi'd rocks, and occur in regions in which thermal waters have been active, tho country-rook would naturally bo more or less changed, and sometimes conipletoly decomposed. In the process of the fornuition of the ore-dei)osit it nniy happen that the ore-material will be entirely removed fn^n tho adjacent rock, or in this rock there may be dei)ositt'd ores that neverexistcd in it before, the ore-nmti'i'ial having been brought from a distance by the [lercolating waters. From the abo\i' it follows that chemical analyses alone, either of the countrv-rock or of its enclosed minerals, lead to unreli- able conclusions as to the source of the ores, as tlu'y indicate only wliat now is in the I'ocks oi" minei-als, and not wlnit might origimdly have been thert'. Jlence it is an unphilosophical jiroce(bu'e to build any gi'ueral tlieoi'v upon such analyses, unless tliev ai'c caret'uUy sup|il"mented by tlu^rough and accu- rate gt'ological study of the I'cgiou in ([Uestion. If, by chemical analysis, any accurate (b'(luctions are to be drawn rcganlinu' the original source ot' the ores, it seems nec- essai'y that we should select those rocks and minerals that are known to be fresh, unaltered and free from any foreign inclu- sions that would intluence the result. Such nnitcrials could only be obtaiicd from recent lava-flows, recently-fornu'il lime- stones, etc.; for no rock that has been I'Xjtosod for a consiih'r- able length ol' tinie to the earth's meteoric agencies can, in the writer's opini(.n, be said to be in its pristine ciMulition. Most aiuilysos of such rocks t'ail to include tests Wn' sutHcieutly minute I 14 ORIGIN AND MODE OF OCCURRENCE OF COPPER-DEPOSITS. 1 quantities of such niatcriiils as comprise the more valuable ore- deposits to permit, as yet, any jj^eneral conclusion to be drawn concernina: the source of all our metals. The nearest approach to anv such analvses is in the meteorites, which are unaltered, and which in composition and structure are closely allied to certain classes of terrestrial basic rocks. These meteorites are found to contain copper, tin, nickel, cobalt, arsenic, zinc, man- ganese, chromium and graphite, and it is probable that more careful and searching analyses would reveal in them and in the lavas other and more precious metals. While it would appear probable that the elements of the useful ores were often originally disseminated through the rocks, particularly the eruptive ones with whicli they are asso- ciated, and were subsequently concentrated by the agency of percolating waters, proofs that this theory is correct are yet wanting — the theory resting mainly upon the observed struct- ure of the ore-deposits, their association and the alteration of the adjacent rocks, or, rather, upon the geological conditions observed, than upon any chemical analyses yet made. To summarize, it may be said that there is no known rock, unless a partial exception be made for rocks in the for-n of glass, tluit will not absorb water to a greater or less extent. All these waters are chemically active, whetlier hot or cold, pure nr inqiure; but it is undisputed that heat, [U'essin-e and substances in solution in these waters greatly increase their chemical activity. It has been iiointed out that all rocks are modiiit'd or changed through the action of the chemically active waters, leading either to the decomposition (»f the rocks or to a change in their mineralogical composition, aiul often to a cimnge in structure. Ft has further been jjointed out that the altera- tion brought about ])y chemical waters, with or without heat and pressure, has caused rocks formerly ot' the same character and composition to taUe upon themselves very diverse forms. It has also been noticed that rocks of entirely ditfen'ut origin and structure, like seii,i2:h the are asso- i^a-ncy of are yet d struet- nition of >ii(litions \VM roek', for-n of ^ extent, or eold, lire and i^e their K'ks are y active or to a eiianire ' altera- it lieat araeter forms. ori trill e been indis- 'node it eer- id de- ORIOIN AND MODE OF OCCURRENCE OF COPPER-DEPOSITS. 15 posited in anijther. A stron_tones and conglomerates, which overlie or abut against the Azoic rocks, and are mainly composed ot the r!.s ot" tlie latter. Tlu'se sandstones form in Miidiigan tlu' base of a new s\stcm of rocks which is generally consid- eretl to be the iH|uivalent of tlie !*otsdam sandstone; hence the rocks are provisionally said to be i'otsdam. South of (^irp ri\er this sandstone can be seen lying against the Azoic ([uartzites and forme" of siiuill voiiis of the formerly overlvitiii* Potsdam sandstone tliat has filled the eracks in tlieso roeks, wiiieh formed bosses or little knobs on the shon's of the old Potsdam sea. The Potsdam sandstone is for.nd overlvinii; mneh of the scri»entiiie of Pres(|ue Tsle where the basement eonu'lomerate is well exposed, altlionand- sterior. aroun, pp. r»!»-71), ami the lime- stone has been considered, fi'om its tbssils, to be of tlu- Trenton or some adjacent lower strata. It was inferred by .lackson that the limestone underlies the sandstone, but by other ob- servers that it overlies it, although no direct contact was seen. 3 ( Pa him tbiit tlie 1 slou in ll had post Stol bn; Am. Jour. Sri, IS'Jl {'.\) xlii., 417-419. \ttvv of [riiit'rly fi tliose •f the •I'lvil)£r Ml' lias Witter. Imd eh 1 oil las saiid- •I'.s of |l'l COM- ■iirivd h'aftT.s .--a 1 1(1- 1 1 ores ''•iiit, I-ast- '(■ I'l'Jlo;-- iiiiT oji -lloi'OS vliicl) liitifs 'oiiif i) or . /.. lias •stcr I in IIIC- rK nl- OCCI liUKNn.; ul-' (.'(M'l'Kli-KKI'nSlTS. 17 Mxcavatiiiiis iiiiMlc l»_v Mr. Ilonnold's |i:irt_v and i'c|M»rt((l hy liiiii liiiVT I'Xposi'd (lie conlact of tilt' two loi'inatioiis, mikI sliow that llif twtt loi'in a sviiclinal or oMoiiii' liiisiii-sli!i|icd fold, with Ihi' liiiicstoiH' oNcrlyiiiii' and in diriM-t contact with the s;iiid- stonc. Tin' existence of this I'ohl in liie siindstoiU', iis wi-ll its in the limestone, removes the dillicidty |irevions ohservers have had in reconcilini;' tin- (»li\ionsl_v tilled liniestom' with the siin- |iosed hori/.ontid sandstoiM', and |iro\-es that llu- l']!islerii sand- )f liower Silurian {( >r(|o\ iciaii) or Cam- stone exiioscd JH're is ( I h hriaii au'c, and older than this Innestom Al the |poinl of contact ot' the two forinalions, e,\|iosed hv e\ca\iitioii, the sandstone and liniestoii c a|i|iear to he coii lormaMe. .ind ihey are seen constantly to au'rce in di|) and strike. The contact hetween the two formations is ahrnnt, w il hind any IumIs of |la^ aithoiiii'h the n|i|>cr layers ol" th an list one contain considcralde carhonatc of lime and may'nesia. and I lie lower laver.-. ot th.' I Mncstmie nnich sdica. These ol)ser\ations an- con>idercd to he conlirmalor\- of the )mmonl\- rec('i\vd \ icw of the I'ofsdaii I a_v Kitstor iiiid Wliiliicv to he iiitfiisiv' iiiiisscs i'ni|iti' iVau^nents of the nndeflyinii' I'oek ; l»y their crystalline strnctni'c hein ji clasojite as a siMJimcntary di'iposit of iiiiiu'ral matter of iiidelinite leiif;tli and deptii. and coin|ianitivei_v siiiall tliiekness, dilTer- iiig in ciianieler from, and |iostei'ior in formation lo, tlie roetcs wliieli inclose it, /.(., tlie .so called sandstone dikes of Dillerand others. 1 OSfTS. lyc (.r K,.. Wfit' cori- '■^ t'IMI|»(f(| '■•^ ill (Ills <»rft'r .111(1 HfW tli.-il iiiiH'd ,,l(- IM'. Til,. I oill l)\- ^vorili, |,v ll.ii' r_\- lie (Tiitcr k'liii;" <((ii- tllc llJISC ihI s;iii(|- ill.li' l;i\;i- <|ilic|ii, dill t:illi/cji- fJijiid OK. (UN AND AUtltl-; oF UCOI'KUKNOI'; OK COl'l'KU-Din'OSlTS. l!> Tlu'sc Hows iDiist li'.ivc taken [ilacc over the i;t'iitly slopliii; tidi'-Nvaslu'd shorts of tliu sea, wliicli sliorc was <^ra(luallv, or if iiiav Im' ut time.' -'MMiittly, sinkiiii;-. . hcyond the I'eadi of the waves. Owinii' '"' the natural iireiiularities o|" a lava-How, and the lU'siiltiiiL:' ine(|indity of' the sedimeiitarv de|iosits, it is to he e.\- jieetcd that some inei|ualilies in thickness of hotli formations should exist, ami that sometimes one ny the oinci- should he waiitinu'. For instance, if a |iortion of the lava was raised aliove till' sea, that |ioi'tion would not he coxci'tMl li\ either saiid>tone or eoiiii'lnmcrate. hut iiiily hy its own decompositictn |irodii.
  • r- lose it, * Tlu'si' (It'si'niiUiiPiis for ll ;;iiiiUl(HU's well' lirsl used hy till' iircsi'lll wi'iliT :iml lati'i' :iilo|iti'(l liy liviiii^. Ah/in n/i tin- (ini/in/jj af llir Irmi mul Cuppfv IHslrlrls of Lilb- Supcriiir, ISSO, pp. <,IS, 107, lOS, lltl, lit;, Pit. I'^-J; I'm,: Am. .I,s.--,c. Ailr. Sri., ISSO, xxix., p. I'2!l; I'mr. Ilnsl. S„r. .\,il. Ili.'«//. l'. S. (Iml. .SV/-., N... 81, iyi)l, pp. 252, 335. •_'<» olildlN AM» MoDK ill' have also hceli adxaiieed, referciiee to which onr limited space does not iiermit. In ISTl' the |»reseiit writer made an examination of the for- mations at the points at which, on the hoiiii'las l|i)ni>'htoii ;md Ifun^'arian rivers, the l'!a>terii sandstone comes in i mitact with the la\as, or, as thev are now commoidv called, the ccippcr- hearinv; rocks (u' Keweemiw :iii -cries, lie foiind that thesund- stoiie, iiisteati of lyiiiLi' hori/.oiilally, dipped iiiadiially or irrcLiu- lai'ly toward the northwest; and th;il. instead of alnittim:' aii'ainst the copper hcariiiii' rocks, it was (»\-erlain hy the latter, and the two were interheddcd. Latci'. the concclni s< df these olisci'vatioiis was denied hy li'\iiii;', who u|>lield the \icw of the U'reater aii'c of the copper-heariiiLi' rocks, hut mo\cd I he supposed sen-shore clitr fnun it- fcU'iini' supposed joinjily :ind phiced it elsev here. Sidisei jUent ly the ipieslion was liikcii up liy Irxiiii:- and ('hamherlin in defence of i he \ icw that I he eoppei'-hcnrini:' rocks are older than the Mastern sMmlslone. Ihii upon stiid\- intaiii the cor- rect iiess of the present writer's stateiueni that the saiidst(Uie _v the Miehii/an (ileolon-icid Survey, tlu'n nndi'r the wiiter's diri'clioii, and the rocks were nncovered aloiin' tin- line of contact of the sandstone and lavas for the |inr|iose ot' ascer- taininu' their exact I'chitions. The result has heen to provt' to the present wi'itc'r, heyond any rcasonahle dcnht, that on the houii'las llonnhton and llunii'arian rivers, as well as on Si'c. 2(>, 'W ">•!, U. .'52 N.,tlie sandstone does di|> u'ently toward the lavas, and linally passes nmU'r them with an increasini; dip; that the Jniiction is not a fault-jmiction itiit that of a lava-How npon an urderU inn' sol't sand and mud. The lowest hed of inelai)livr was foMiid on the hoiiii'las ilouii'hton river to he ovei'lain l»y sandstone, iis descrihed hy the writer in 1 SSO, idthoiiu'li tliis fact had liecn denied hy the hcfore-incntioned anthors. Thi' copper-liciirini;' rocks on the north side ol' |)oii<:;las lloun'hton I'ivcr are seen to o\erlie the I'lastern sandstone for ahoiit lAO feet. Alonii' the line o|' contact to the north on tlu' St. Louis location and in Wall raxiiie, as well as south of l*ortai>-e Lake, proof of distinct faultinii* could hi' olitained. which sushiins tlu' fault claimed hy Fostei' ami Whitney, Ii'vini^ and others. Alonii' the houii'las II(Uii;'ht()n I'outait, no sii:;ns ot'any fault, or hut few siti'us. were found ; hut in the copi)er-hearin,tions of sides, were ohsei'\t il, that woidd indicate a faultiuu' here. '^riie fault-plane, wlii'revcr oh.servi'd alon;.;' tlu' line of contact, showed that the hani;inii"-wall was on the side lU'xt the eopiiei'- heariuu' rocks. It is well known hy all miners and li'eolo- y-ists that in all luu'iual faults, I.e., tlu' cotutnonly occiirriiiii; faults, the rock on tlu' hau^•iu^■ side of the fault has slipped down relatively lo the rock formimi' the foot-wall. A reversed fault is oiu' in which the hanyinii-wall side has heen pushed up lili OKKIIN ANIt Mnlti: ul" UC(M lUlKNCK (»!' ntl'I'Klt-IMM'nslTS. oil tlic t'oot-Willl side (if lilt' I'illllt. 'I'lif I'cNCI'sed lillllls iil'c ufll- (•I'lllly r(»|l>iilt'l'i'(| to Itc I'ill'c: so liilli'li so lliiit solilt' Llt'oloy'inls (Itiiv tliiil lllfV ex «'l' occur, illlliollii'li tilt- |ifcsc|it wiitcl' lijis seen tlu'lll iisstn'iiilcd with lioriii;il l';iiill> in tlic CliccVci' ori'-licil ill I 'oft Henry, New ^'(l^l\. This rjirc iiioch' of I'anitiiin' is the one iissiiiiicd l)y lr\iiii:', who wiis olili'^cil iils<» to iissiinic tliiit the ii|>- lil'l of the hiiii!iiiiLi'-\\ ill! Wiis iiccoiii|)iiiiic(l hy ii thnisl to the I'listw iiry rrofessor A. I'!. SeiiUKin. woiihl Sllstilili ; lull these, the |irescllt \\ riler thinks, need more ciiicl'lll e.\illllillillioli Mild I'lirtiiel' coiiiinmitioli hefole tlie\ e;ili he iie- ei'|ited ;is colicliisivf. cilice :ill the ohserved fiicts eiili he e\- [dniiied h_\ the re|ieiite(i iiiovcnieiils tliiii ii--ii:dly occur nloiiy the si(h's of a fault The prest'iil writer hoMs that the saiid>to|ie iindelTles tlie co|i|ierdieariii<:' rocUs. and thai the lii>t la\a of that series lh>wed o\-er tin; Masterii sandstone, which is older than the co|>|(erdiearinn' or Keweeiiawan series. Siilisec|iieiitly a fault- line or lissiire was formed, riinniiiii' la'ar what is now the |ii)iiil of contact o|' the >aii(Uloiie :ind la\as, soiiieriiiies exactly at that point, soineliincs on the la\'a >ide. and in'ohahly so!iietinie> on the sandstone side of it. Aloiiy' this ti.siire it i> |irol)al.|e that a iionnal taiilt occurred, aloiin' which, hy the sli|i|i.iiiii' down of the haiiii'ini;" <'i' we(li:t'->lia|ied side, the saiiilstoiies and their interhedded Iava> were more or less lieiit downwanls or coii- torti'd, as they are now found to he. 'I'his normal fanltiiii:- accounts for the fact that sometimes the la\a ami >oiiietimes its associati'd coiiii'loineratc is hroiiiiht in contact with the l"]a>tern saiitlstoiie aloiiLf the laiiltdiiie. It is to he reineinhered that in almost all faults there i^ more or le>> rnhhiiiii- hack and forth, or i|»-aiid-dowii iiiotioii, althoiiLih the linal r*'sull of these varied in I'ioiis is the prodnclioii of a re\crse(| or normal fault, accord- iii;j,' to the direction in which ihe i^'reatest amount ot' motion fools |ilace, 'I'his \ iew would e\|ilaiii most of the diHiciilties that i;-e(do- jH'isIs have hail in iinderstandinL;' this series. es|ieeially if it should lie shown that the lava-tlows came from the main laki'- side instead of troiii the Iveweeiiaw I'.ay side, as that would only re(|iiire the cut-oil" feinnants of the edn'es of the lava- th)Ws to he reiiio\'ed h\ demidatioli (Ui the i\eweeiiaw r»a\ side. nUIdlN \NI) M|n'r-l»t'aiiiiii" rofUs uiHiltl n|>|»('iii' to lif iinnt' iin'Cffi iliiiii tliiit (il" Ifxiiiii', uliilf ii iii»riiiiil I'miiIi wttiilij lif fii<:lili»M. .Iiifksiiii Mini Miiii'dii. tli:it tlif t()|i|n'r- liviiiiiiii' rtM'ks iii'f t'i 'ri'nissit' iir I'liimiiiu" iKiiii'iliidiiiiillv with il.iiiiil iiiiirt' ttr It'ss riiiiltiii;;' ncfiirs iiIdih;' lln'st- lissiirt'-jiiifs. rm'tiiii't' liiikt' lio ill !i Irmiiili fxciiviitcd iiltniL;' I'lic ol' tlit'sf lissiict's. wliilt' iiiiiiiv lit' till' (itlifi's iii'f lillt'il with \ fiii-iiiuttcr, wliifli hits hffii iiiiiifil III :i iiTfiitt'i' t»i' less t'\li'iit. 'riit'st- iViictiil'i'S niid lissiii'i'^, with liiiiltiiii;' iHi'iiss Ki'Wt'ciiiiw I'liiiit, |»riili:ili| v w t'lf dt'\ i'lii|iril sidist'i|iii'iitl\ til till' tiiiiiiatiiHi III' till' liiiiLi'itiidiiiiil I'iiiill 111' t'iiiilts, it' iimir tliiiii mil' siii'h tliiill shidl hitfi' lif |irii\id to t'\ist. ShiMild siii'h III' tlif riisi', it wiMilil iiriiiiiiit I'nr |i;irt III' till' ;i--illiiril I hiiklii'ss III' till' hfds. 'I'iif lict'iil r-liHliliiiliril lissill'fs st'i'lil til liilXf lict'li I'dniii'd hy ImiWiII'mI lll>»Vt'IIH'llt> III' dill'i'l'i'lll |iillts III' tilt' rnrkslhilt rilllst'll till' I'lnss-rfih'tiifi' Mild disliirntiiui (il lilt' latlt'i'. Tlic iiiii\f- iiji'iits u fit' it'|pi':ilfil rrmn tiiiic In litiif . caii^iiiu' a nililiiiiij;', ii'riiidiiiLi', linakiiii:' and iiidisjiinu' nl tin- parts adjari'iil to tlu- lis>iii'i'S. A I'tii- llif main ii^siii'fs hail liffii I'lirnif d, tlif siilisf- i|iii'iil iiiiiVf iiif Ills wi'iild iiiil laiisf an\ \t'i'\ i'\tfnsi\t' sfftindacy lirfakiiiLi' III tlif fiini|ia(l and lifa\y lifds nl' diahast' ami fuii- 'jjiinif lalf , lull in llif --1111 and sfmiaffiiiis mt'la|iliyi'> ihf iVaf- tiii'iiiii' u niild III' iiimli li'i'fatf I', sii that tin- jiai'ts ;nr|aii'iit In tin- lissiin's wiiiiltl lif miifli lii-nkfii. hiiriiiu' tlif tiiiif ut' thf I'l'af- tiiiiiii:', and siilisfi|iif nt ly, llifsc lissiiffs sfi'Vfd as fhainifls for thf flifinifally aftivf watci's. whifli also pf rfolati'd thioiiii'li t III' adjaf fill links. In thf sforiaffoiis and fasily dffominis- ahlf niflapliyis ihf \t'iiis Wfi'f w idf iifd hy llif dfioiiiposilioii of f III' adiaii'iit rmk. hut in thf foarsfly ffystalliiif and lifa\y diahasfs, as a riilf. llif saiiii- ciri'its wiif |ii'oi|iii'fd filliiT not at all or only to a limitfd fxlfiit. 'i'lu' samlstoiu's and con- •iioiiif rates, lifiiiLf fiiiii|iiisfd |iriiifi|ially of t racliytif and rliyo- litif inaif rial, ai'f niiifli Ifss airfflfd hy |ii'riolatiiiu' waters than thf hasaltif rocks; lii'm-f thf lissiiifs are m>t gfiierally uidoiiotl 24 OmOIN AND MODE OF OCCrRRKNCR OF COPPER-DEPOSITS. in them, cspi'oially iftliov arc in tliick 1)cm1s. At tlio time wlicii tli'.' prrcolatinii' waters were actiiiu* on i\w rocks adjacent to tho fissures, tlu V Were also workinii' in tlu' rocks everywliore upon Keweenaw I'oint. In many localities tlu- evidence is stronu' tliat tli(> percolatinii' >va1ers were Iiot, wliile in others, as reniai'ked l»y Mai'vine. no siy-n exists that they wei'c ahovi' the temperature of the watei's of till' presi'ut day. These waters jtereolated with more or K'ss rt'adiness thronii-h the roeks, causiuL'' a u'r^'ater (n- less alti'ration antl decay, while tiie suhstauces they took up were ome other minerals. Ucsides copper, the (h'positctl minerals are niainly (|uart/C, calcite. epidote, laumontitc, pre hnite. dclessitc, chlorite, datolitc, anah ite. orthoclasc, .ipophyllite. etc. All, or nearly all. of the materials that Mil the cri'vices, cells and other places in tlii' la\as and conu'lomeratcs appai'ciitly were derived from the de- composition of the la\as thcms(dves, and the course ot' the waters carryinii' these materials in solution seems to lia\i' iieen do\ nw;ird. T\[v fissures that form tlh' veins were tilled at the sanu' time and hy the same r^'encies as ihosc that acted upon th ■ rocks, and the materials in them likewise appear to ha\'e heen ohtnined from the adjacent rocks themselves. In the iiarrouci' portions the \-cins are often tilled with the \ciu matter proper, hut in the wider portions the veins are often composed ot' hrokeu-up massi s ol' nu'lapliyr, etc., cementeil hy \'ein- nuitter. In the \eins the copper is found intinuitely nii.\e(l with the U'aiiu'ue, or in she* ts or irrcii'uiar masses. In sheet-form the cojiju'r exteuils dow nwai'il or has its sides approximately paral- lel with the \ciu. Ot'ten the sheet is dixided, and holds he- tweeu its parts some ol' the u'anu'Ue or mclaphyr. It is also not inicomnioii to lind, entirely enclosed in the copper, masses of iiielaphvr, i|iiart/, calcile or other vein-materials. The nitda- [ihyrs thcmscK es arc oflen inipi'eniuiicd with copper atljacent OUKJIN AN'lt MOUK i)V OCCUKKENCE OF ('(iri'lMMiKIMiSlTS. 25 he he ml- l>c- nls.. ;st'S ichi- •clll to tlir vt'iiis. (Jood illuslnitions of llic veins ciin lie seen iit 11k' I'liti'iiix, dill', Ccntnil, Coiipcr Kails and oilier mines in KeWHH'naw count y. Tn the \ieinity ol" llaueoek, Ilonu'liton anited in their mass • lillerent minerals associated with more or less cwiijici'. The co|i|)er is i^'enerally deposited in an irrcii'ular manner in the nu'laphyr, I'orminu' strings, i^ioli, des, ii'r<'!^'nlar masses. ( Ic. Tliese deposits ai'e not in the I'orm of \eins, hut arc ini|ireun:t- tions ot'old la\a-lloW's. and hencr are in the t'orni oi' heds. As an example of nunes wcu'ked upon these old laxa-tlnws then' may he cited the <>uincy. l''i anklin, < )sceola. Atlantic, llnron, ami the ('oppi'r l''alls in part. The ('opjiri b'alls has iieen worked ill pari on an ohl la\adlo\\ ol' a Ncry scoriaceoiis char- acter thai l'ormc(l orii^'inally a iilack. rou^•h, cellular lava-sheet coscred wlih clinkers, similar to many well-kiu'wn modern la\a- llows. Al the tlliie ot' the t!o\\ , or after it. the inh'rsticcs Wcl'e tilled willi dcli'ital mini, while the \arious parts of the llow appear to lie coniiecled. and do iioi form li'iic watcr-\\(U'n peh- hles. 'I'hc writer has collecled at ('opper j'^alls oortions ot' the rock thai show the hardenc(| e\|ei'i(U' cru>t and the cellular intcrioi', ;;< lhc_\ occur in small nia>se> and hoiiihs of modern la\as. w liile he has found prcser\fd Inlact the oriu'inal I'opy. slrimz'W Iwir-ted surfa<'c of the la\a. The ('oppel' Fall- hed, aliove descrilicil. is locally called the a>li-lie(|. Iml it i- a nicla- ph\r or a triU' lava-llow. ami not a IhmI of volcanic a^h^■^. The Atlantic mine appear> to he workc(l upon the same or a -iiuilar I'ormatioii. I '.e>idc> the \ I'in- and la\ adlow s, the con ■clonic rates lia\ e also heeii t'oiiud in place- to ha\(' had their iiiLu'-licc- lllird in wiih eopper and other mineraU. In them the old eeiiicniinu' mud. and ojieiit iiucs the pel il lie- of nu'laph \ r. ha\ e heiai reinoNcd hy percolalinu' \\:iters. and llicii' places lille(l wiih copper, which pi'iictralcs e\('ii the iiiiiiiite crack< in llic hard rhyoliie (tpiarl/- p(M'pli\r\) pelihles. These old sca-heach eoiiLt'lonicratcs arc now worked in the ('aluinet and llecla. the Tamarack, the Alloiie/, and other mines. Tlnie are thus mine(| in this rcu'iou three distinct classes of deposits: 20 ORTOTN AND MODE OF OCCtlHRENCE OF OOPPER-DEPOSTTf!. Coppci'-DcposHs iif KcirretKiir Point. 1. Vein-deposits (tissuro-vcins), '2. Flow-deposits (iiielai)liyrs or iimyji'didoids). 8. Tx'd-deposits (eoiiii'loiiiei'iites). Tlie eoiiiiloineriites iwv known to he old sea-lteiieli deposits, liki' lliosi' lliat are t'onninti' alonu" tlie lake or ocean at the jti'esent time. This is proved h_v tlu' ronnded and water-woi-n eharaeler of Iheir pi'hhles and urains; h_v the ohsei'ved water- action on the snrl'ace of the undi'rlying lava-th)\v: and h_v the tact that at tlicii itase the con i^'reater ahnndance where thei'c ai'c to ln' seen the tnost siii'ns of water-action. Had the copj»ei' heeii de]>osited hv iii'iicous aii'cncics snhseipientlv !o ihe formation of the nnda- phyr and coiiii-loinerates it wonld lia\'e had a channel or line ol [lassaii'e, and wonld ha\e hcen continnoiis alonu" that line, so that all the ditferent n'asses ol ccppcr wonhi have hecn con- nectetl toii'cther downwai'd. unless separated h_v fractures or faults. 'i'he cop|»er seems to have needed for its de|K>siiion tlu' open spaces of veins and lissui'es. and rocks that were porous ami cellidar, or those whose parts wim'c easily removed hy tlu' per- colatinu' waters, like nu'lajphyi's or the cemeiitiui:' mud of Ihe conii'lomerates. In i ruth, i he •■op|ier seems to hasc hcen de- po,-«itei| wliercMT there wcri' found any places in which to leave it. From the fad that the copper is i;'i lerally found iiuist ahun- daii'h' under the hea\y la\ a-llows, and associateil with minerals evidently the prodiwt of the decompitsed lavas, it apjx-ars pi'oh- ahle lluL t he copper was once finely disseminated throuu'li the hivas, and has since hecn concentrated h,- watt-rs |iercolatin<:' through them, This view is advoeated hy Midler, l>aiierniaiin, IH' or It'll iiiil nT- .Ir- mii- nils r..l.- nil!' inn. ORKUN AND MODK OF orcURRENrK OF COPPEK-DEl'OSITS. 27 MiirviiU' ami myself, wliilc u siiiiilar view lias het-ii advanced hy S. V. Kmmons to aceomit loi' the origin and coiieeiitration of the Leailvilh' <»i'i'-de|M»sits.* Had the eopper heeii deriv«'d iVom llie sandslones, then om- would suppose that under tliem should he louml the «;Tealest siijiply of eo|»|ter; hut such is not llu' ease. That the course of water deitositiiiii' the co|»|ier was ;i:enerally downward is indi- cated hy (he finding- of spiUes ol' copper and eah-ite that i-.xtend from one hed down into otln'i's, with tin- sniall end downward, like an icicle; hy the fact that when the copper is not uniformly distrihiitt'd (hrouuiioii! the hed or tlow that is mined it is often, altlioun'h not always, more almndant in its upper portion; ami !ty the fact that the lari;'esl masses of copper have usually hceii found in the upper portioi s of the veiiis. That the c(tppei' was deposited after the copper-hearinij,' series was complete is shown hy the fact that it is found in fissures extcndiiiii' aci'oss the heds that could only have Ik'cii produced after tlu' heds were in jilacc: hy the fact that the copper was deposited suhse((Ueiitly to the Joiiitiiiu' of the lavas, owim; to its MOW heiiiii' found wrapped aroiiml the pieces formed hy joint- iiiii"; and hy the extension of the copper from one tlow down into another as a continuous mass. The means hy which the copper was conceiitratecl and d*-- posited as native copper, iiislead of occurriiiii' iu the form of t he usual copper ores, is an iiitcresliiiLi' and as yet iinsoKcd prohlem that awaits th*' attention of the chemist who is willin>;' to liive his time and tlioiinn;mii, (/nitrl. Jonr. (ikiI. A'oc,, IS(l(i, XII., IIS 111;!; W;iils\\H)rtll, .Vo/i.s on flir (uoIdijii nj till- Iriin (inti ('upper DlHtrirlx, ISSl), p. I'Jti; Kiiimolis, (('((i/oy// (i)i(/ Miitliifi liKliiMri/ of lAddvill,; ISSi;, pp. ;57S, ;57'.». t (Iwl. of Mich., 1S78, I., part II, p. 14. 28 'MU(UN AND MOI>K OF orCURRKI, V. OF COri'KR-DIill'OSITS. wi'i'i' iU'k'tl iipoM l>y iHTcoliitiiiii,' Wiili'i's, hotli hot aiul cold, Ity wliicli i\u' I'di'ks wiM'i' iiltoiH'd to ii ti;i'i'alri' or 'I'ss cxU'iil, aiid tin' ('o]»|K'r was coiu't'iitraU'd and stored up •;i the coiii^loiiu'i'- atc's, lavas and xciiis in whicli it is now lonnd, I'lu' altoN r account ii'ivcs in ln'ici' :<. li^'ticral idea ol" the i:'eoloii'_v of the I'cii'ion touclu'd Mpou li' re, as tln'writiT intei'pi'i'ts tlii' facts olisi'Tvi'd. lie is, however, awai'c that dillerent infei'|ii'e- talions of fill' same facts are made hvotluTs. He has tliei'cforc called special attention to the important ditrcri'nces of interpre- tation. In the cop[n'r-i»earinii" rocks, thi' (piestioii of tluir rela- tion lo the Kastt'i'n sandstone is one of u'reat economic interest and (lee > s hafts. ()ni' can in tliesi' (lavs of diamond dril readily see this when one considers t hat it involves the (pies- lion. Do the copper-heariiiii' rocks extend out under the Eastern leir expioi'alioii hi'comes nierely sa mist one or iiofr' Ifthevdo, tl a (piestion of how u'reat thickiu'ss of sandstone must he hored tliroiiii'h. If thev do not, then the (piestion oUii'ht to he .-^ettled hy the