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ZXVIII, 1859.] ^t^^^^^^^^0^i^^H^^^t*^^*^^^'^i^^^9^^^^t^^^^^0^^*^*^^^^ti'^0^^0*^^^^^*^^^^t0*^>^'^^^^*i^^^^ ■i'^ ''>i'. ON REACTIONS OF THE SALTS OF LIME, Ero. I rr ^:jH ;'■ i^ :j;',,i. The importance, in a geological point of view, of gypsum and of the carbonates of lime and magnesia in the forms of limestone, dolomite and magnesite, has led me to make a series of re- Bearches, whose results serve to explain many things hitherto obscure in the history of these substances. I propose in the present paper to describe, in the first place, certain cbemical re- actions of the salts of lime and magnesia ; and, secondly, to con- sider the principal facts in the history of gypsums, and magnesian rocks, and the theory of their formation. I. On the action of solutions of bicarbonate of toda on taUs of lim and magnesia. 1. In studying some years since the geological relations of alka- line mineral waters I ^und that b^ tne action of a solution of carbonate of soda, a partial separation of the salts of litne from magnesia could be effected. Subsequent experiments, made with dilute solutions of bicarbonate of soda, have led me to the follow- ing results. If to a solution containing besides common salt the chlorids of calcium and magnesium in the proportion of one equivalent of each, we add a solution of bicarbonate of soda in water satu- rated with carbonic acid, there separates a gelatinous precipitate, which very soon becomes crystalline. Collected and ';vashed i after a few hours, it is found to consist of carbonate of lime with but a small proportion of carbonate of magnesia, which in three successive precipitations from the same saline liquid, was found j to equal 2*20, 2*00, and 1'23 per cent. The proportion of sepa- rated carbonate of magnesia diminished as the magnesian salts predominated in the solution, which now gave no further preci- Sitate with bicarbonate of soda, but yielded by evaporation to j ryness, a granular residue of hydrated carbonate of magnesia, i with very little lime. In this way, a litre of the solution gave 4'19 grams of carbonate of magnesia, (MgO, COa) and only OU grm. of carbonate of lime, while the soluble portion still retained in the form of chlorid, 1*176 grms. of magnesia, but no lime. * The experiments detailed in the firat section of this paper, as well u Mint in j the second, li:iva appeared in the Report of the Qeol. Survey of Canada for 18(7; I the others of this section, to||;ether with those of the third, are from the forthcomiM I Report for 18S8. See also thisJournal, [2] zzvi, 110, and the Canadian Joiiniil| for May, 1869, p. 184. Many of the original obserratioos in the fourth MCtiool Already been published in Uia Reports of the Survey, but are now for tbiM| time Drought together. and the formation of Gypsum and Mdgnesian Rocks. 9 2. A portion of the saline solution from which about one-third of the lime had been separated as above by bicarbonate of soda, gave by thirty minutes ebullition, a precipitate which for a litre equalled 0*666 grm. of carbonate of lime and 0-173 of car- bonate of magnesia. Another portion of the same solution when evaporated to dryness at 120 F., gave 0*805 of carbonate of lime, but no magnesia. 3. If in the preceding experiments we employ a somewhat dilute solution of bicarbonate of soda there is no immediate pre* cipitaiion of carbonate of lime. A solution was prepared with one litre of water, 29*2 grms. of sea-salt, 18*8 of chlorid of calcium, 507 of hyd rated chlorid of magnesium, and 10*0 grms. of hydrated sulphate of soda, the three chlorids being in the proportion of two equivalents of tl" first and third to one of chlorid of cal- cium. In another litre of water were dissolved 42*0 grms. (equal to two equivalents) of bicarbonate of soda, and the lic^uid was then saturated with carbonic acid gas. Of this solution, 500 cubic centimeters would have been required to decompose the whole of the chlorid of calcium in the first, and 200 c. c. of it [were gradually added to this with stirring, but without pro- Jucing any visible eflfect. A further portion of 100 c. c. caused I slight turbidness, which was soon replaced by a crystalline precipitate, adhering to the sides of the vessel, and gradually in- creasing in amount. After a repose of forty hours at 68* F., the precipitate was collected and analyzed. It weighed 4*8 grms., and I m carbonate of lime, with S'3 p. c. of carbonate of magnesia. 4. The saline liquid, augmented by the washings of the preci- pitate, now measured 1*400 c. c. ; of this one-half was mingled with 100 c. c. of the alkaline solution, being the quantity re- quired for the decomposition of the remaining lime salt. No immediate change was apparent, but at the end of twenty-four hours there had separated a crystalline precipitate, weighing 2288 grms., and consisting of carbonate of lime with only 2*6 p. c, I of carbonate of magnesia. 5. The reason of this separation of lime from magnesia in the I ibove experiments is evident, when wo consider that carbonate of magnesia at ordinary temperatures decomposes the soluble salts of lime. Thus, according to Mitscherlich, magnesite or do- lomite slowly transforms a solution of gypsum into one of sul- Ipiiate of magnesia, carbonate of lime being formed at the same I time. I have observed a similar reaction between dolomite and Imltttion of chlorid of calcium, especially at about 125° F. De |Seiiannont, and after him Bineau, found that solutions of bicar- ate of magnesia decompose chlorid of calcium in the cold, or |«t temperatures below 212 F. with precipitation of nearly pure learbonate of line, although the assertion of the latter^ that sul< IpUteoflime is decomposed by the some agent, i8> aa I shall l.^l I I M' ?j iit; ^t; .'1 .. f * n 'A. ii 4 On some Reactions of the Salts of Lime and Magnesia, l?/'>s'. y.-l F-)*- .;^<; ^M-H- • "I- i: ».', presently show, not quite correct. The power of decomposing jgypsum appears to belong only to solutions containing monocar- Donate of magnesia. 6. When a portion of moist recently precipitated hydro- carbonate of magnesia is added to a solution of bicarbonate of | lime, it is immediately dissolved, but the transparent solution soon becomes turbid from separation of carbonate of lime. A similar reaction is produced by carbonate of soda, which precipi- tates carbonate of lime from a solution of the bicarbonate. 7. The preceding experiments show a remarkable degree of I solubility in recently formed bicarbonate of lime ; the liquid in [ § 4 deposited spontaneously an amount of carbonate of lime equal to 2*6 grms. per litre ; and if we add, as in § 2, 0*8 grms. for the amount of carbonate remaining in solution, we shall have| 3'4 grms. of carbonate of lime held for a time dissolved as bicar- bonate in a litre of saline water, at the ordinary pressure of the I atmosphere ; the experiment detailed in § 3, indicates a solubility at least as great. Boutron and Boudet, by treating lime-water with carbonic acid, obtained supersaturated solutions holding 2 "3 grms. of carbonate in a litre, but the half of this was soon deposited, and they found I that a litre of water charged with carbonic acid, under a pres-l sure of several atmospheres, cannot retain more than 1-16 grms.! of carbonate of lime in permanent solution. We have seenial § 2, that a saline solution retains after some hours exposure, 01 grms. of carbonate. In other trials I have found 0*888 and 0915J grms. of carbonate of lime in pure water saturated with carbonic I acid at the atmospheric pressure. A solution prepared under a I pressure of several atmospheres with excess of carbonic acid,| and then exposed for twelve hours in a loosely covered vessel,! still retained 0'730 grms. of carbonate of lime in a litre. Bischof) estimates the solubility of bicarbonate of lime at one part inf 1000, which may be regarded as correct. I Lassaigne found a saturated solution of bicarbonate of lime to) contain six equivalents of carbonic acid for one of lime; butfroml an experiment of Bischof it would appear, that an amount d\ lime equal to 0'59 grms. of carbonate to a litre may exist in solu-f tion as sesqui-carbonate. — {Lehrbuch der Geologie, ii, 1126.) 8. According to the same author, when a current of carbonic! ac'd is passed for a long time through water containing purej magnesia in suspensson, there is dissolved a quantity equal toj 1-35 grms. of carbonate of magnesia to a litre. — {Ibid., i, 38I,)| Under certain conditions, however, water is capable of dissolving! an amount of carbonate of magnesia many times greater tbaul that stated by Bischof. In § 1 we have seen that a litre of waterj containing at the same time chlorids of sodium and magnesiuniir may hold dissolved as bicarbonate 419 grms. of carbonate of mag- and the formation of Gypsum and Magnesian Rocks. 6 I jesia; and by adding known quantities of carbonate of soda to a solution of chlorid of magnesium and passing a current of carbonic acid through the mixture, I have found it easy to ob- tain permanent solutions, containing not less than 21*0 grms. of nionocarbonate of magnesia in a litre. Bineau, by prolonging for several days the action of carbonic acid, obtained a solution which contained in a litre 11"2 grms. of magnesia (equal to 23'5 grs. of magnesian carbonate), combined with very nearly two equivalents of carbonic acid. The observadons of H. Eose, and of Longchamp, show that the presence of alkaline chlorids, sulphates or carbonates, as well as of magnesian salts, increases the solubility of carbonate of magnesia in water. This may explain the great difference be- tween the determination of Bischof, in which all foreign salts I vere excluded from the solution, and the experiments of Bineau myself, with solutions which always contained salts of soda I or magnesia. That the presence of such salts does not, on the contrary, augment the solubility of bicarbonate of lime, is appa- I tent from §2. 9. Bineau found that during the spontaneous evaporation of H solution of bicarbonate of magnesia carbonic acid escaped, and Itarbonate of magnesia separated, until at length the liquid re- Itained in a litre only from O'lO to 0*17 grms. of carbonate of mag- nesia, with sufficient carbonic acid to form a sesquicarbonate. Such solutions, when transferred to closed vessels, were sponta- neously decomposed, hydrated carbonate of magnesia yparating Uhile a bicarbonate remained in solution. — {Ann. de CIdm. et cfe |%«., [3],li,302.) This spontaneous decomposition of the sesquicarbonate of mag- Iresiainto monocarbonate and bicarbonate is somewhat analogous to that exhibited by a recent supersaturated solution of bicarbon- ite of lime, which as we have seen, breaks up into an insoluble nionocarbonate and free carbonic acid or a very acid salt. The reaction is observed in a remarkable manner during the evaporation of certain saline mineral waters, which contain abun- dance of bicarbonate of magnesia. A portion of water from the Plantagenet spring was left to evaporate in an open basin in uamraer, until its volume was reduced to one-fifth. The clear solution was then decanted from a crystalline crust of car- bonates of lime and magnesia, and transferred to a carefully closed flask, where after two or three days, it deposited a strongly Udhereut crust of hydrated carbonate of magnesia, chiefly on the lower parts of the vessel. The amount of this deposit was equal I to 0772 grms. of carbonate of magnesia to a litre of the concen- Itrated liquid, which contained no lime, but abundance of bicar- wte and chlorid of magnesium, after the separation of the I precipitate. li: if- I- ■v :: a H-. - ■ ■ 'i i:,t.\ ^ ;:■ On tome Reactions of the Salts of Lime and Magnesia, m ■ ■r !>.■ , '•' '■t;sh' K;-!.*- '■»■'. I ,. ■ n. On the reaction between solutions of bicarbonate of lime and the sulphates of soda and magnesia. 10. If to a solution of bicarbonate of lime vw add a portion of sulphate of soda or sulphate of magnesia, there are formed by double decomposition, bicarbonate of soda or bicarbonate of I magnesia and sulphate of lime, which latter salt may be precipi- tated by the addition of alcohol. To 400 cubic centimeters of a recently prepared transparent solution of bicarbonate of lime there were addea two grams of hy- dratcd sulphate of soda, and the solution was then mingled with an equal volume of alcohol of 90 p. c. A white flocculent precipi- tate immediately appeared, v/hich was collected after a few hours, and washed with dilute alcohol. It was completely soluble in water, but was again thrown down by alcohol, with the addition of a few drops of hydrochloric acid, and was pure sulphate of lime, weighing, when ignited, 0*428 grms., which corresponds to 0915 j grms. of carbonate of lime to the litre. 11. 400 c. c. of the same solution of bicarbonate of lime were j treated with 2*0 grms. of crystallized sulphate of magnesia and alcohol, as above; the precipitated sulphate of lime equalled 0"467 grm. The filtrate from which the alcohol had been expel- led gave by boiling, a copious precipitate containing a little lime j and 0276 grms. of carbonate of magnesia; theory requires 0'288. 12. 500 c. c. of a recent solution of bicarbonate of lime witii I 2*0 grms. of hydrated sulphate of soda and an equal volume of j alcohol, gave a precipitate of gypsum, which when dissolved in I water and reprecipitated as in § 10, gave 0'570 of sulphate of j lime, equal to '838 grm. of carbonate of lime to a litre. Thealk«- line filtrate was evaporated to dryness, the residue redissolved, and precipitated at a boiling heat by a dilute solution of chlorid I of calcium. The carbonate of lime thus obtained was fi-ee from I sulphate, and corresponded to -445 grm. of carbonate of soda; theory demands "442. 13. In consequence of this formation of gypsum, the solubilitrl of carbonate of lime in carbonic acid water is, as I have founa, j very much increased by the presence of sulphate of soda, or i phate of magnesia. To a little more than 200 c. c. of lime-water I were added 4*0 grms. of sulphate of soda, and a stream of careftiiljl washed carbonic acid gas was then passed through the liquid for j four hours, at the end of which time the solution of the carbon- ate of lime was nearly complete. On the addition of an eq volume of absolute alcohol, there fell a precipitate of g^rpsuni, I which, when washed, eflfervesced slightly with hydrochloric acid from a trace of carbonate of lime ; but being again thrown down I from its aqueous solution by alcohol, gave 0*555 grms. of ignited ■''Hi' and the formation of Oypsum and Magneaian Rocks. 7 lulphate of lime, equal to about 2*0 grins, of carbonate of lime to t litre. The carbonate of soda in the alkaline filtrate was found, by the indirect method of § 12, equal to '484 grm. ; theory re- hires '482. 14. In another experiment, a dilute solution of sulphate of I loda was treated with an excess of bicarbonate of lime, in order to determine whether it were possible to decompose completely the soda-salt by this means. After throwing down the gypsum by alcohol, the residue contained for a litre 1080 of carbonate I lod 0*520 of sulphate of soda. 15. 250 c. c. of water, containing ;;en grams of hydrated sulphate if soda, and two grams of pure carbonate of lime, were exposed I for an hour and a half to a current of carbonic acid gas, and the Ulution was then left for four hours in a covered Hask, after kbich 150 c. c. of the clear liquid were mixed with an equal Irolume of absolute alcohol. A copious precipitate was formed, |fhich, after twelve hours, was collected; it was completely solu- ble in 200 c. c. of water, from which alcohol threw down '348 grms. lofsulphate of lime, besides a farther portion of '020 grs. from Ithe evaporated filtrate, making a total of 868 grs., equal to 2*420 1^. of sulphate of lime to the litre. I 16. 200 c. c. of a similar solution to the last, gave with alco- lliol, a precipitate of gypsum, which was readily soluble in water, lud being thrown down as oxalate, gave an amount of carbonate |of lime equal to 1*820 grms. to the litre, or 2*475 of sulphate of me. 17. A current of carbonic acid gas was passed for an hour ind a quarter through a solution containing sulphate of magne- ia and carbonate of Time. The filtered liquid remained transpa- lient after many hours exposure to the air ; but 200 c. c. of it Ipve with alcohol a precipitate of gypsum, which was collected lifter twelve hours and was completely soluble in water, from Iwliicli solution the lime was thrown down as oxalate, giving an limouut of carbonate equal to 1*565 grms. or to 2*128 grms. of sul- Ipliate of lime to the litre. The alcoholic filtrate by evaporation Ito dryness over a water-bath, gave a little carbonate of lime, and ]an amount of carbonate of magnesia equal to 1*100 grms. to the 3; theory requires 1*812, but it is difficult to separate in this Iway the whole of the carbonate of magnesia from an excess of iBulphate. 18. It thus appears that in the presence of sulphate of soda lor magnesia, water saturated with carbonic acid is capable of jdissolving nearly twice the ordinary proportion of carbonate of jlime, or from 1*565 to 1*820 grms. to the litre. The lime in these liquids is doubtless to be regarded as existing chiefly as sul- fate, of which salt they are nearly saturated solutions. The Beterminations, in § 15, § 16 and § 17, give respectively one t; . ■ t ' « *. ^ > ■;: .^ 8 On tome Reactions of the Salts of Lime and Magnetia, ).■» ' ». I; "^v M .".V. ; ''.;.' ^ ■ i ■■„• . ., part of sulphate of lime for 413, 404 and 459 parts of water.; The solubility of this salt in pure water has oeen variouslyl stated. According to Bucholz, one part of sulphate of lime re. I quires 460 parts of hot or cold water for its solution; but Giesel gives 380 parts of cold, and 888 of boiling water, its soiubill ity being increased, according to O. Henry, by the presence ofj sulphate of soda. — (Gmelin, Handbook^ (Cavendish ed.,) iii, 202.)| I determined the amount of sulphate of lime in a solution pre! pared by agitating frequently for several days, pure artificially prepared gypsum, with distilled water, at 60 F. The lime wasl thrown down as oxalate, and indicated one part of sulphate ofl lime to 488 parts of water. Another portion of the same solu-f tion was evaporated at a gentle heat until crystals of gypsum I separated, and the clear saturated solution decanted from tl crystals after twelve hours of repose at 60° F., contained onel part of sulphate of lime for 872 parts of water, which approaches! closely to the determination of Giese. 19. In a late paper, by Bineau, on the earthy carbonates! already cited {Ann. de Vhim. et de Phys., [3] li., 297), the authorl refers to a memoir of Mr. E. Marchand, who asserts that a litrel of water may hold; dissolved as bicarbonate, about 2 5 grms. ofl carbonate of lime, and that sulphate of lime and alkaline bicarboaf ates may co-exist in natural waters. These statements are con-l troverted by Bineau, but the latter of them is fully sustained byl the experiments which we have aescribed, while the augnientedl solubility of the carbonate of lime is to a great extent explainedl if the solutions of Marchand contained soluble sulphates. I havel not however been able to verify the assertion of Marchand, thatl sulphate of lime separates from mixed solutions of bicarbonate ofl lime and sulphate of soda, unless indeed by the intervention ofl alcohol ; although as will now be shown gypsum may be crys-l tallized from mingled aqueous solutions of bicarbonate of lime| and sulphate of magnesia. 20. "When a solution like that of § 17 is evaporated at i gentle heat, it might be expected that carbonate of lime, beings less soluble salt than gypsum, or the carbonate of magnesia,! would be deposited. I have found, however, that from such aj solution under these conditions, gypsum separates, while bicarT bonate of magnesia remains in solution. Tho sulphate of mag-j nesia employed in the following experiments was carefully re- crystallized and contained no traces of lime or free acid ; its solal tion did not alter the color of curcuma, but slowly restored thatj of reddened litmus. The carbonic acid employed was evolved I from limestone hydrochloric acid, and carefully washed, so thalj its solution was not troubled by nitrate of silver. J To 500 c. c. of water were added twelve grams of sulphate ofl magnesia and half a gram of precipitated carbonate of lime, andl and the formation of Gypsum and Magneaian Rocks. jcurrcnt of carbonic acid gas passed for two hours through the liquid, when the carbonate of hmo was nearly all dissolved. The Solution was now evaporated in a porcelain basin at a tempera- uirc varying from 90 to 110° F., until crystals of sulphate of ;u;,giicsiu scparutcd ; a little water was then added ana the so- Mulioii, being immediately fdtered, contained no lime-salt, but La3 strongly alkaline to curcuma paper. When heated it be- came turbid before boiling, and after llfleen minutes ebullition deposited aflocculent precipitate containing -208 grm. of carbon- ate of magnesia. The basin in whic' he evaporation had been coiKlucted was covered with a crystalline crust which elfervesced but slightly with hydrochloric acid; it was soluble in a large volumt! of water, and was principally gypsum. 21. To 800 c. c. of water were added twenty grams of sulphate lof magnesia and one gram of pure nrbonato of lime; a current of gas was now passed through the liquid for an hour and a half, jhen the lime was nearly all dissolved; the solution was satu- jrated with the gas, but contained no trace of chlorine. It was laeutral to curcuma, and gave with alcohol a precipitate of gyp- Isjm. A portion of it heated to boiling remained clear for five Lnutes, but then grew turbid and depositc .1 an abundant pre- Itipitate of carbonate of lime. I 200 c. c. of this solution were e^apcrated at a temperature of ISlf-lBG" F,, until crystals of sulphate of magnesia separated ; lifter twelve hours repose in the cold a little water was added |>iid the solution decanted from a precipitate, of which '272 grm. here collected ; when this was treated with hydrochloric acid and Iclilute alcohol a portion of carbonate of lime was removed and iliere remained "236 grm. of crystalline gypsum, weighing when lijimted, '185, equal to "920 grm. of sulphate of lime to the litre. iTlie filtered solution of suljjhate of magnesia was strongly alka- jline to curcuma, and gave by boiling, a precipitate which coii- lined no lime but a portion of carbonate of magnesia equal to I WO grm. to the litre ; theory demands -570. 22. A solution of twelve grams of sulphate of magnesia in lOOc. c. of water was mingled with carbonate of lime and satu- I rated with carbonic acid. It was then filtered and evaporated lat about 160° F., until sulphate of magnesia separated. By this Imeans a sparingly soluble crystalline precij)itate was formed, [which contained gypsum equal to •235 grm. of sulphate of lime, 'a little carbonate. The filtrate gave by boiling a precipi- Itate of carbonate of magnesia which equalled •098, while theory Iclemands •I-IS. To 000 c. c. of a solution of bicarbonate of lime were added Ituenty grains of sulphate of magnesia, when the liquid which has before turbid from a portion of suspended carbonate, became [clear, and gave by evaporation at 90° F. a precipitate contain- •ECOXD 6EU1KS, Vol. XXVllI, No. 83.-SEPT., 1859 '¥ \ v \ ■i , - 1 w |f^ .■■■I: J U> m T' '' !•>. ■ny t'-:!'. i ■'.. ^-i'-'.*- ' 10 On some Reactions of the Salts of Lime and Magnesia, ing -154 of sulphate of lime, with some carbonate of lime and a trace only of magnesia. A solution of five grams of sulphate of magnesia was mingled with a portion of solition of bicarbonate of lime, and evaporated at 160°-180'' F., further portions of the latter, amounting in all to 800 c. c. being added as the evaporation went on. There was deposited a mixture of carbonate of lime, with crystalline gypsum equal to "373 grm. of sulphate of lime to the litre. 23. It will be remarked, that while the recent solution con- taining g3'psum and carbonate of magnesia with excess of car- bonic acid is neutral to curcuma and may be boiled for some minutes before a precipitate of carbonate appears, the liquid from which gypsum has been deposited by evaporation is strongly alkaline to curcuma paper, and lets fall a precipitatej of carbonate of magnesia, even before attaining the boilingl point; this precipitate is in part redissolved as the liquid cook when this alkaline liquid is mixed with a solution of gjpsum it deposits in a few hours, especially if gently warmed, a crystal-! line precipitate of carbonate of lime, resultmg from the decom-j position of the sulphate of lime by the carbonate of magnesia. The sulphate of magnesia retains the carbonate of magnesia ii solution in such a manner that the latter is not rendered com' pletely insoluble, even when the liq^uid is evaporated to dryni over a water-bath. Hence the deficiency observed in the deter minations of carbonate of magnesia in § 17, § 21 and § 22, wbei a large proportion of sulphate was present. The filtrate froi the carbonate in these cases is still alkaline, and gives wii lutrates of silver and copper, precipitates of carbonates. 24. In the preceding experiments all salts, other than tin concerned in tne reaction, were excluded, but similar results obtained in the presence of sea-salt and chlorid of magnesiui Twenty grams of pure chlorid of sodium, and ten grams of soil phate of magnesia, with a portion of carbonate of lime, wei added to 800 c. c. of water, and the solution saturated with bonic acid gas. Of this liquid 400 c. c. were evaporated at 160' 180* F., until sea-salt separated, and gave '045 grm. of sulphal of lime, mixed with '291 of carbonate. Ten grams of chlorid of sodium, and twenty grams of crysl lized chlorid of magnesium were added to 600 c. c. of solution bicarbonate of lime, containing two grams of sulphate of magi sia; 300 c. c. of this solution were now evaporated at 160' 180* F., until crystals of sea-salt appeared ; there were obtaini •057 grm. of sulphate of lime. 25. A saturated solution of one part of sea-salt and two pai of sulphate of magnesia was exposed to a cold of 32° F., when large amount of sulphate of soda separated. The mother liquoi Gontaiuiug besides some sea-salt and sulphate of magnesia, mth( k vess lines m{ iquids I ate olume, i of lime and a and the formation of Gypsum and Magnesian Rocks. 1 1 large amount of chlorid of magnesium, was diluted with four parta of water. 500 c. c. of this solution were mingled with carbonate of lime, saturated with carbonic acid, and then evapo- rated at a temperature of 85°-90° F., to one-twelfth, when crys- tals of sea-salt separated, and a crjrstalline residue of gypsum was obtained. It did not effervesce with hydrochloric acid, and was soluble in a large volume of water. The saline liquid by evap- oration to dryness, gave '331 of carbonate of magnesia. To another portion of 100 c. c. of the saline solution employed in the last experiment, 500 c. c. of a solution of bicarbonate of lime were graaually added, the mixture being meanwhile evapo- rated at a temperature below 100° F., and at length carried to dryness. On treating the mass with water, the strongly saline filtrate was found to contain no lime-salt, but sulphate of lime was abundant in the washings, and the residue on the filter, vhen treated with hydrochloric acid, left crystalline grains of Ijypsum. I 26. In the foregoing experiments it is not easy to separate the [more soluble salts from the gypsum, which, although insoluble I saturated saline liquids, is readily dissolved by washing with liater, in place of which a solution of gypsum may be used. In |tither case, as a solution of sulphate of lime is decomposed by ibe dissolved carbonate of magnesia, the washings should not be Imngled with the alkaline filtrate in which we wish to determine lltiis salt. As a solution of magnesian carbonate which has lost I excess of carbonic acid by evaporation is incompatible v/ith iJissolved gypsum, it is evi4ent that the presence of an excess of Ihis acid must be one of the conditions required for the crystal- lization of gypsum from such a solution. It ofl«n happens that lome slight variations in the conditions of the experiment with Itwo portions of the same solution, will give in one case abund- |ince of gypsum and in the other chiefly carbonate of lime. 27. The power of bicarbonate of baryta to decompose sulphate lof magnesia and even sulphate of soda with precipitation of sul- Ipliate of baryta is well known ^ and I have found that the inso- lubility of the sulphate of strontia determines a similar result. |A solution of bicarbonate of strontia, prepared by passing car- onic acid gas through water holding the carbonate in suspen- pon, was divided into two portions, one of which was mingled lith a portion of sulphate of soda and the other with sulphate |of magnesia. The mixtures, at first clear, socn became troubled om the separation of a precipitate, which adhered to the sides of Ike vessels, and like arnmonio magnesian phosphate, along the lines marked by the rod in stirring. After twelve hours the liquids decanted from the precipitate, which was in each case^ kulphate of strontia, were evaporated at a gentle heat to a small Volume, during which process they deposited a portiou oi oar- .;. -SI '■r ■ t1 ♦ j; m-i f-m -.•.;♦■■ ■, V ^ •> ' W::- ^■\ ■'•.. . ' (. ^t.V :'••) 12 On some Reactions of the Salts of Lime and Magnesia, bonate of strontia. The first contained some sulpbate, with a large proportion of carbonate of soda, and the second, which gave no trace of dissolved strontia,, let fall by boiling a copious precipitate of magnesian carbonate. An analogous reaction between tie sulphates of iron and zinc and bicarbonate of lime, resulting in the production of gypsum 1 and carbonates of zinc and iron, has already been suggested by ! Monheim to explain the association of these minerals in a modem deposit from the waters of a mine. The experiments of Biscbof have established the fact of such a decomposition for the sulphate of copper, as well as for the sulphates of zinc, and protoxyd of I ixon.—{Lehrbuch, ii, 1198-1202.) m. On the formation of the double carbonate of lime and magnesia. 28. The carbonates of lime and magnesia, although so fre- quently combined in nature in the form of dolomite, exhibit,! under ordinary circumstances, little disposition to unite witli| each other. The carbonate of lime, as we have seen, separates! nearly pure, from solutions of bicarbonate of magnesia, at ordi-l nary temperatures; and if by the aid of heat a portion of magne-l siaii carbonate is at the same time precipitated, the two appear! to be only in a state of admixture. f Karsten long since observed that dilute acetic acid, at tempera-l tures below 32° F., readily dissolves carbonate of lime, but igl without action on the double carbonate of lime and raagnesi»,| which constitutes dolomite. By this means he was enabled tO| make a proximate analysis of many magnesian limestones, which Ive found to be mixtures of dolomite with carbonate of limeJ Before undertaking a series of experiments on the production of this double carbonate, I endeavored to fix by experiment tM limits of error in Karsten's process. 29. For this purpose I took a pure acetic acid, containing 291 p. c. of glacial acid ; this was mixed with an equal volume ol water, so that the dilute acid used in the following experiment! contained about 15 p. c. of glacial acetic acid. Unless otherwis specified, it was employed at 32'' F. (lower temperatures bein^ difficult to regulate), and this temperature was maintained byj bath of ice and water. In these conditions the acid dissolve precipitated carbonate of lime and pulverized limestone witlj lively effervescence, even when farther diluted. A pure cm talline dolomite in fine powder was however slowly attacked subsiding to the bottom of the liquid, and disengaging sma bubbles of gas from time to time. After six hours digestion! with a large excess of the acid at 32° F., 1-68 grs. of this dold mite had lost '082 of carbonate of lime, and '068 of carbonaM and the formation of Cfypsum and Magnesian Rocks. 18 of magnesia, equal to 8*63 p. c. of dolomite, (containing 48*5 p. o. of magnesian carbonate). At a temperature of 60" F., the same tcid caused a slow but continued disengagement of gas bubbles from the powdered dolomite, which after 30 hours lost 28*0 p. c. of its weight, the dissolved portion containing 45*0 p. c. of car- I bonate of magnesia. At 126" F. the action of the acid upon the vdered dolomite was accompanied with gentle eflfervescence, I and the amount dissolved after two hours digestion, was 18*6 per cent. A white crystalline magnesite from Styria, whose only impu- rity was a portion of carbonate of iron equal to 0*9 p. c. of per- joxyd, and which was slowly but completely soluble in hot hy- drochloric acid, was also slightly attacked by dilute acetic acid jt60° F. ; after twelve hours digestion there were dissolved 0*68 Ip. c. of the carbonate. At 125" F. however a distinct ef&rves* Icence was produced with the acid, and at the end of three hours IllO p. c. of the magnesite were dissolved. 1 From these experiments it was evident that although not insol- lible in acetic acid of 16'0 p. c. at 32° F., this liquid might serve llo separate dolomite from carbonate of lime, and also at a higher llemperature to effect a partial separation of dolomite from mag- iKsite. 30. The insolubility of the double carbonate of lime and Inagnesia in carbonic acid water is also an important fact in the history of dolomite. Bischof found that by the prolonged action 'a solution of carbonic acid upon a limestone containing 11*54 |p,c. of magnesian carbonate, tnere were d'ssolved 4*29 p. c. of Itarbonate of lime and not a trace of magnesia. In like manner Imanganesian iron-spar, which contained 14*0 p. c. of carbonate If lime and 150 p. c. of carbonate of magnesia, gave to carbonio fcid water four parts of carbonate of lime for one part of magne- ian carbonate. — {Lehrbuch, ii, 1176.) 31. Accepting the idea that dolomites have been formed \>j alteration of beds of carbonate of lime, Haidinger long tince suggested that a solution of sulphate of magnesin at a temperature might produce this change, giving rise by Bouble decomposition to carbonate of magnesia and sulphate of Ime, although Mitscherlich had shown that at ordinary tempera- kres sulphate of lime and carbonato of magnesia are mutually ^composed (§ 5). Von Morlot subsequently verified this con- «turc of Haidinger ; he found that by heating together to 200° lentigrade, for six hours in a sealed tube a mixture of two equi- kalents of carbonate of lime and one equivalent of crystallized fcicihate of magnesia, the latter was completely decomposed, litn the production of sulphate of lime and carbonate of magne- pa, which he seems to have regarded as forming with the excess ' carbonate of lime a double carbonate. — (Liebig and Kopp, J'. '1 \: fi ';- 'iH ( ■ , , ' *■'■ fit \' ■ !■'■• u '" ? i^'*-' ^v I ; I" H fk •* 14 On some Reactions of the Salts of Lime and Magnesia, • Jahresbericht, 1848, ii, 500). Desirous of verifying this observa- tion I have repeated the experiment of von Morlot, but have found that although the sulphate of magnesia is indeed com- 1 pletely converted into carbonate, this remains for the most parti m the form of magnesite mechanically intermixed with the| excess of carbonate of lime, which may be separated by the i of dilute acetic acid. 82. 100 parts of pure precipitated carbonate of lime (two equi-l valents) and 123 parts of crystalized sulphate of magnesia (one! equivalent) were intimately mingled and exposed in sealed glassl tubes for six hours to a temperature of 392° F. (200° C.) Thel resulting white tasteless mass was treated with cold dilute acetic! acid which immediately caused a strong effervescence. Wheal this action had subsided the residue was washed with cold waterl and then treated with dilute hydrochloric acid which produced! no effect in the cold, but by the aid of a gentle heat dissolved al large portion with effervescence. The addition of alcohol threvrl down abundance of gypsum from the solution, and the filtrat( from this being evaporated to dryness and then moistened with hydrochloric acid, was digested with absolute alcohol, by whichj the chlorids alorie were dissolved, leaving a small residue ol eypsum, and were found to consist of chlorid of magnesium mm but very little chlorid of calcium. The acetic acid on the conl trary had dissolved a large portion of carbonate of lime with bull little carbonate of magnesia and a little gypsum. Thus in ona experiment the acetic solution gave besides '079 of sulphate, •623 of carbonate of lime and 'OlS of carbonate of magnesia, equal t 8 p. c. of the dissolved carbonates, while the portion insolublij in acetic acid, separated from gypsum by the process just dei scribed, gave '459 of carbonate of magnesia and '017 of carbonatJ of lime, or 96'3 p. c. of magnesian carbonate. In another exi periment there was obtained from the residue insoluble in acetia acid, carbonate of magnesia '437, carbonate of lime "020. The crystallized suTphate of magnesia undergoes the aqueoa fusion at about 230° F., and contains sufficient water to rendei the mixture with carbonate of lime somewhat moist after I ing. The above experiment v/as however repeated with the adl dition of a portion of water, but with the same result as beforef the carbonates not dissolved by acetic acid consisted of "242 ( carbonate of magnesia and '008 of carbonate of lime. 33. The experiments of de Senarmont have shown that whei carbonate of magnesia is formed at a temprature of 150°-175°C by the reaction between solutions of sulphate of magnesia m carbonate of soda, or by the decomposition of a solution of I carbonate of magnesia, it separates as a crystalline powder spai ingly soluble in acids and apparently identical with raagnesitt — Ann. de Chim. et de Phys. [3], xxxii, 148. It is evident f" .■If and the formation of Gypsum and Magnesian Rocks. 15 the results just detailed that a similar result takes place when carbonate of lime is substituted for the carbonate of soda, the carbonate of magnesia formed in the presence of an excess of carbonate of lime retaining only three or four per cent of this 1 carbonate. 34. According to Marignac, when carbonate of lime is heated I in sealed tubes with a solution of chlorid of magnesium to 200° C. for six hours, there is obtained, besides a portion of chlorid of cal- cium, a product consisting of 48"0 parts of carbopate of lime and 1620 of carbonate of magnesia; at the end of two hours' heating, Ithe proportion of magnesian carbonate was less. {Bui iSoc. Geol. \k France [2] vi, 318.) It does not appear whether Marignac ex- lamined the product by the aid of acetic acid, but I find that in ItUs process a double carbonate of lime and magnesia is really I formed. A. mixture of six parts of pure precipitated carbonate of lime jifith five parts of pure crystallized hydrated chlorid of magne- IsiQm, dissolved in a little water, was placed in sealed tubes and heated for eight hours to a temperature of 150° C. which was Ipdually raised to 220° C. Two hours after cooling, the mat- Iter was removed from the tubes, washed, dried, and treated jwith dilute acetic acid, which caused a violent eflfervescence ; as Inoii as this had subsided, the filtrate, which contained a large lacess of acid and still attacked carbonate of lime with energy, l?as separated by filtration from the undissolved residue which Ivas but little more than one-fifth of the whole. The dissolved Iportion consisted in 100 parts of carbonate of lime 96*86, carbon- |tte of magnesia 8*14. 85. Previous experiments had shown me that in operating fith glass tubes, a portion of silicate of magnesia is always [formea,* and as this is decomposed by mineral acids, acetic acid I employed in the analysis of the undissolved carbonates, of ffhicli 'SOO grm. from the last experiment were treated with acetic *The glass of the tubes is always more or less attacked in these experiments, ktr. alone at the temperature employed dissolving from it a portion of alkaline ilicate, which by double decomposition with carbonate or chlorid i^ives rise to a sili- ^te of magnesia. A mixture of carbonates of lime and magnesia witu water and Brbonate of soda having been heated for t A hours in glass tubes to \hQ°-\1(P p. the greater part of the magnesia was found to be changed into a light flocculent rdrated silicate insoluble in acetic acid, but decomposed without effervescence by igestion with hydrochloric acid, which took up a lar^e portion of magnesia with mlyatrace of lime, and left granular silica. I have not yet obtained this silicate ia nffirient purity to determine. its precise constitution. Wlien a mixture of magnesite and crystalline quartz was heated for several weeks Ji a copper vessel with a solution of carbonate of soda to 180° C. it was found that parly the whole of the quartz had been converted into a hydrous silicate of magne- I, after decomposing which by sulphuric acid the now soluble silica could be ilten up by a boiling solution of carbonate of soda. I reserve for another place the Niiltt of a series of researches upon the artificial formation of silicates by the reac- w of silica upon carbonates, which as I have elsewhere shown pl^s a most import- ft part in the chemical alteratioD of sedimentary rocks. — Proc, Uoyal Society, and I Journal, [2], zxiii, 437. •>,. l: r >f . f1 V- i 'i^.' i .■'-' ■ •4; .■(•, »3 1 ■!' ■■•■ : ii • ' . -tii ) ^;^!/ ^''d- X}' Mm fe \, .\J m \i if' .■■*#, N-'. ^[' M^' 16 On some Reactions of the Salts of Lime and Magnesia, acid of 1.5 p. c. at 60° F. No action was apparent even after some minutes, but with a heat of 120° F. a gentle effervescence ensued. When this ceased there remained a flocculent residue equal to 15'7 p. c, and the undissolved portion gave carbonate of lime 37'6, carbonate of magnesia 62*4. A portion of '500 grm. of the same carbonates was now diges- ted with dilute acetic acid at 60° F. for several hours. The soluble portion contained carbonate of lime 40*0, and carbonate of magnesia 60'0, while the undissolved residue equalled 224 p. c. It effervesced freely with warm somewhat dilute hjdro- chloric acid and left a silicious residue of •032 grm., while the dis- solved portion gave '007 of carbonate of lime and '060 of car- bonate of magnesia. 36. In another experiment with carbonate of lime and chloridj of magnesium, the mixture of carbonates as extracted from tl tubes container 244 p. c. of magnesian carbonate. This wl treated with acetic acid at 60° F., and the digestion continued foi some length of time, the result of which was that a large portioi of the double carbonate was taken up and the dissolved portioi contained 11*4 p. c. of carbonate of magnesia, while the und solved residue was carbonate of magnesia with but 303 p. c. carbonate of lime, and in a third experiment under similar cir^ cumstances contained only 23'6 per cent These experimeDi were made before I had determined the solubility of tne doubl carbonate in acetic acid at the ordinary temperature. It is evident from the above results that these magnesian bonates, which retain after the action of acetic acid from 23 87*0 p. c. of carbonate of lime, are mixtures of a double carbonj ate of lime and magnesia with a less soluble carbonate of nmgDt sian, from which the double salt may be partially separated bj the prolonged action of acetic "acid at ordinary temperatures, shown in § 35. 37. In the experiments § 34 and § 36 it appears that the bonate of magnesia unites, at the moment of its formation, with portion of carbonate- of lime to form the double carbonate. It mained to be seen whether mixtures of the two carbonates woali combine directly, and experiments were made with the Stjrii magnesite (§ 29) which was mingled in fine powder with Ci bonate of lime and heated for some hours in sealed tubes to2l" C. with a dilute solution of chlorid of calcium. No combinatioi took place, and the carbonate of lime was afterwards completeij removed from the magnesite hy cold dilute acetic acid. The dense insoluble magnesite, as might be conjectured froi its occurrence in the products of the previous experiineiitvS, ei hibits none of that aptitude to combine with carbonate of which seems to characterize the newly formed magnesian bonate before passing into this sparingly soluble condition, aisitc _ W anai 28(SiM' .' types 'OND se: '■•!:■ J*.1 Magnesia, and the formation of Gypsum and Magnesian Rocks. 17 •ent even after le effervescence icculent residue gave carbonate chauge as we have seen in the experiments of de Senarmont (1 33) takes place at from 155" to 175° C. The hydrated carbon- ates of magnesia formed at low temperatures and readily soluble in dilute acids, are in like manner, when heated under pressure, to prevent the loss of carbonic acid, converted into magnesite ; if under these conditions carbonate of lime be present the two combine to form a double salt, possessing the chemical characters of dolomite.* 88. In his researches on the double carbonates, H. Deville has at dilute hydro-Htecribed an anhydrous crystalline salt composed of one equiva- m., while the dia-Hjent each of the carbonates of magnesia and soda. This double carbonate is insoluble in cold water, but readily dissolves in icetic acid. "When it is heated with a solution of chlorid of mag- lesium in sealed tubes to 200° C. chlorid of sodium and spar- liagly soluble magnesite are obtained. When warmed witli a lution of chlorid of calcium this double carbonate is decom- ised and gives rise to a mixture of carbonates of lime and mag- lesia readily soluble in acetic acid; at a higher temperature der pressure the two carbonates unite to form a double salt. 39. Three parts of the finely pulverized carbonate of magnesia id soda were added to two parts of chlorid of calcium dissolved a little water and rendered slightly acid by hydrochloric acid. le mixture being placed in hermetically sealed glass tubes, were heated for some hours in a bath of boiling water with uent agitation, and then in an oil-bath for eight hours, the mperature being slowly raised from 130° to 220° C. On ling, the saline liquid in the tubes was found to contain, be- es chlorids of sodium and calcium, a considerable amount of lorid of magnesium. A portion of the double salt became ted over by the precipitated carbonate of lime and thus pro- ted from the further action of the chlorid of calcium. The carbonates from the above experiment were treated with a ■ge excess of dilute acetic acid at 60° F. till effervescence ceased. grm. of the residue were now digested for two hours with lute acid at 60° F. ; the action was accompanied with a slow constant disengagement of carbonic acid gas, and the solu- in gave '302 grwi. of carbonates, of which the carbonate of lime itituted 41-3 p. c. The undissolved portion effervesced with 1 1 have shown, from a consideration of the densities of the rhombohedral car- [ipare, that supposing them to possess a common aton»>, volume, we may rep- kcalclte by 15(C2M206) while dolomite and chalybite are 18(C2M206) and pesite and carbonate of zinc (smithsonite) 20(CaM3 06). Farther examples Joljrmerism in mineral compounds are seen in silliraanite and cyanite, in meionite Itoisitc (saussurite), and in hornblende and pyroxene. These latter, accepting Tttte analyses of Rammelsberg. may be represented respectively by 26(SiM03) |28(SiM03), wollastonite being 22lSiM03); these formulas correspond to k types of liomceomorphous isomeric silicates. (See this Journal, [2], xvi, 203, lCwip(c» Rendus de VAcad. 1855, xli, 79.) f ONI) SERIES, Vol. XXVin, No. 83, SEPT., 18S9. 24 was now diges- al hours. The ), and carbonate LC equalled 22i and -060 ofcail ' lime and cblorid| ctracted from tt onate. This w tion continued foi lat a large portioi dissolved portioi , while the um" ;hbut80-3p.c. , under similar cit' ?hese experimeni ility of the doubl rature. Bse magnesian ci e acid from f a double carM irbonateofmagw Lially separated \ y temperatures, 1. 1 .,' ii •w;. # 18 On some Reactions of the Salts of Lime and Magnesia, !>■ i ■■ ^S-^ ji ! V ..■.;»■ ■i| ..■■■ «-'V'' •warm hydrochloric acid, which dissolved "178 of carbonates con- taining onl^ 12*3 p. c. of carbonate of lime, leaving -116 grm. of insoluble silicious residue. 40. In a repetition of the above experiments the carbonates were treated with acetic acid at 32° F. till effervescence ceased, and a portion of the remaining double carbonate was digested for some time with acetic acid at 125° F. which took up 80*0 p. c. of carbonates containing 884 p. c. of carbonate of lime. The in- soluble portion did not effervesce with hydrochloric acid, which however removed from it a portion of magnesia but no lime, and left a silicious residue. Another portion was digested for several hours with acetic acid at 60° F. which took up 78"0 p. c. of car- bonates containing 40*8 of carbonate of lime. The insoluble residue effervesced freely with warm sulphuric acid, which dis' solved a portion of magnesia but no trace of lime. 41. Other experiments were made in which carbonate oi lime was mingled with solutions of sulphate of magnesia and car- bonate of soda, so that carbonate of magnesia would be formed, the sulphate of magnesia being in slight excess in one case am the alkaline carbonate in another. In another experiment, mixture of ter-hydrated carbonate of magnesia and carbonate oj lime with water and carbonate of soda, was employed. All o| these were heated in metallic tubes to from 130 to 200° C. the products digested for a long time with acetic acid at 60' These experiments were made at a time when I had not detei mined the solubility of the double carbonate under such coi ditions, and the consequence was that the residues obtained wei chiefly carbonate of magnesia, which was scarcely attacked cold acids, but retained in the form of the double salt fror. 'ij to eleven per cent of carbonate of lime. In another trial, hoi ever, a mixture of hydro-carbonate {magnesia alba) and carbo] of lime with water and an excess of bicarbonate of soda was posed in the boiler of a steam engine to a temperature of 120° to 130° C. for several hours every day auring ten weel The washed residue was then digested with acetic acid only effervescence ceased; after which it was completely soluble in drochloric acid, and gave carbonate of lime 46'3, carbonate magnesia 53*7. 42. The preceding experiments show that carbonate of mi aesia, whether (1) as magnesia alba in presence of excess of bonic acid, from bicarbonate cf soda, or (2) a ter-hydrated carl ate, or (3) as precipitated by bicarbonate of soda from sulpl of magnesia, or (4) by carbonate of lime from a solution of rid of magnesium at an elevated temperature, or (5) as sepa from the double carbonate of magnesia and soda by a solutioi chlorid of calcium, will in the presence of water unite with carbonate of lime to form a double carbonate of lime \Facts 43. I Ijthe ..^ir. and the formation of Gypsum and Magnesian Rocks. 19 ihe carbonates ice ceased, and 18 digested for k up 80-0 p. c. lime. The in lie acid, wMcli ut no lime, and estedfoTseverall 78-Op. c. ofcar- The insoluble' acid, wUcli dis' le. ch carbonate ol nagnesiaandcar vould be formed 8 in one case am ler experiment, I and carbonate ol employed. AH 01 30^ to 200° C. 8 petic acid at 60 I I had not detei B tinder such coi dues obtained wei arcely attacked \ oublesaltftoF"' another tnal, bo^ alhd) and carboi ' ite of soda was ■mperature of 7 during ten weeij icetic acid only r )letely soluble int » 46-3, carbonate t carbonate of ice of excess ot ter-bydratedcai soda from sulpl a solution ol " J or(5)as8epa sodabya.soluti^ ivrater unite 1 Si" [;•'■! ;'i*. h.': :^-.i' 20 On some Reactions of the Salts of Lime and Magnesia, {Am. Jour, SciA Comptes JiendijA or Onondaga salt group of the same region.- [fi], vii, 176 ; Report Geol Survey, 1848, 150 ; de VAcad., 1855, xl, 1348.) These acid waters which make their appearance in an almost undisturbed region, I conceive to have their origin in deeply buried strata, where gypsum or other sulphates may bejunaer| going decomposition by the action of water and silica at an elfr vated temperature, a process analogous to that which gives rise to exhalations of carbonic acid gas. 44. Waters containing free sulphuric acid or ferric or alumin ous sulphate, may by flowing into basins where carbonate oi lime is present, give rise to solutions of sulphate of hme, am the evaporation of these, of sea-water or other gypseous sola. tions must give rise to deposits of sulphate of lime, which wi belong to the first division mentioned above. These modes oi formation however do not account for an important fact in thi history of most stratified gypsums, which is that of their almi constant association with carbonate of magnesia generally inth form of magnesian limestone. Beds of dolomite are often intei stratified with 'or include beds or masses of gypsum, while dol mite and carbonate of magnesia are sometimes found imbedd( in gypsum or anhydrite. For a description of the mami which is disseminated in the gypsum of Salzburg, scaDi noy, Mineralogie, 2d ed., ii, 424, Small masses of compi and crystalline gypsum, occasionally associated with crystals o| calcite and quartz, abound in some of the dolomite beds of tbi so-called Calciferous sandrock in Canada, and crystallized _ sum and anhydrite, together with sulphates of baryta and stroi tia, and fluor spar, occur in geodes in the magnesian limestom of Niagara. The anhydrous sulphate of lime not only foi beds by itself but is often met with disseminated in m grains or crystals through beds of gypsum, and even interstra^ fied with it, as in the south of France, in the Hartz, Switzerlaiii' and in Nova Scotia, as described by Mr. Dawson. (Acadian ' ology, 225.) The conversion of beds of anhydrite into gy[ by the absorption of water, and the attendant phenomena, k been described by Charpentier. 45. Both the hydrous and anhydrous sulphate sometimes foi the cement of conglomerates or breccias, which enclose flinl fragments of shale and of limestone, as at Pomarance in Tuscan] (Scarabelli, Bull. Soc. Geol. de France, [2], xi, 346,) and also i Bex, where the cement of the conglomerate is a granular anlij drite (Charpentier, Ibid., [2], xii, 546). Gypsums moreover often include clay and sand, and somel contain a considerable admixture of carbonate of lime, r in those of Aix, according to Coquand, amounts to eight cent. The gypsums of Montmartre also contain, according Thesd mica,] and the formation of Gypsum and Magnesian Rocks. 21 Delesse, besides some clay and sand, and several hundredths of carbonate of lime, not less than three per cent of soluble silica intermixed. Silica in the form of flint or chert is sometimes found in concretions with gypsum ; thus in the miocene clays near Bologna in Italy, flints are met with associated with sul- phates of lime, of baryta and strontia, together with pyrites and sulphur. Masses of sulphate of strontia are likewise found in clays with the gypsums of Montmartre, and the association of sulphate of strontia with the sulphur, gypsum and rock salt of Sicily is well known. The gypsums of Madrid, which occur in tertiary clays, are according to Casiano de Prado, accompanied by beds of chert and of magnesite {Bull. Soc. Geol, de France, [2], xi, 334). Besides the rock salt which so often occurs with gypsum, we may here recall its frequent association with the sulphates of soda and magnesia, both of which are found in very many places imbedded in gypsum, or intermingled with rock-salt or with the associated clays. (Bischof, Chem. Geology, ii, 421-431.) Large deposits of both of these sulphates occur with gypsum and rock- salt in Spain ; in Nova Scotia also sulphate of soda is found in gypsum with boro-calcite, an association worthy of notice from the occurrence of boracite, both crystallized and massive (stass- furthite) with gypsums in Germany. — (How, Am. Jour, of Science, |[2], xxiv, 230.) 46. The gypsums of the class which we are now describing I appear in every geological period. To these apparently belong the .0(1 asses of gypsum and anhydrite, which at Pahlun are asso- ciated with dolomite and serpentine in the chloritic bands of the oldest crystalline rocks of Scandinavia, the probable equivalents of the Laurentian system of North America. On this continent the oldest known gypsums are those already mentioned as occur- ring near the base of the palaeozoic series, and in what is called by the geologists of New York the Calciferous sandrock. As we ascend the series gypsum is occasionally met with in the Clinton and Niagara groups, until we reach the Onondaga salt-group in the Upper Silurian rocks of Canada and New York, which con- tains great deposits of dolomite and gypsum, occasionally accom- panied by sulphur. The gypsums, anhydrites, and brine springs of Nova Scotia belong to the Carboniferous series, while the fre- quent recurrence of gypsum in Europe through all the higher rocks up to the Miocene' inclusive, is too well known to require I notice. 47. The so-called primitive gypsums and anhydrites, which I in the Alps and Pyrennees occur interstratified with crystalline jfichists, are now known to belong to altered secondary strata. jThese gypsums enclose many crystalline minerals, such as talc, I mica, epidote, hornblende, dipyre, beryl, quartz, hematite, blende •. f. ' h n.l ■■M > .' i wm :,S. tA Wit: -.1 I",,',. ■ i.'":'r f '■'i': ^ V * '<:• i: .J..-. •„ ^. i ill f ri • f..i >,^ Mr ?fi;- .■■ Iff •H, 22 On some Reactions of the Salts of Lime and Magnesia, and pyrites. At Saurat in the Pyrennees many of these mine- rals appear in the vicinity of a mass of granite which penetrates and alters both fossiliferous limestone and ^psum. The latter becomes mingled with and finally passes into limestone. (Co- quand, Bull. Soc. Ghl. de France, [1], xii, 845.) In Algiere, where gypsum is associated with crystalline limestone, gneiss, amphibolite and serpentine, small crystals of beryl are found disseminated alike through the limestone and the gypsumJ Some of the gypsums of the Eartz, according to Frapom, con- tain nodules of a silicate of magnesia colored by carbonaceoosl matter, and having the soilness and the chemical composition of I steatite.— (/ij"c?., [2], iv, 882.) 48. The marine origin of the greater number of gypsiferoosl formations is evident both from the accompanying rock salt and I the associated fossils, but certain gypsums (as well as certain | dolomites,) have evidently been deposited in fresh-water basins. A gypsum from Asia Minor examined by Ehrenberg contains a i great number of fresh-water polygastric infusoria, and beds ofl gypsum occur in the lacustrine basins of Aix and of Auvergne;[ the gypsiferous strata of the Paris basin are also regarded as ofj fresh-water origin. 49. Besides the magnesian limestones of gypsiferous strata I great deposits of dolomite occur in the rocks of every geologicalf period. I have long since described the dolomites which form J extensive beds, often associated with ophiolites and withcrys-l talline limestones, in the Laurentian system in Canada. Great! portions of the palseozoio limestones of North America are mag-[ nesian, especially in the valley of the Mississippi,* while depositsl of dolomites are found in Europe alike in the Permian, Tnassic,! Jurassic, and Tertiary strata. Mr. Dana has even described i * For the following facts with regard to the dolomites of tho paloiozoic rocb ofl the Mississippi valley, I am indebted to Prof. James Hall of AllMmy. We ban! there in ascending order : I 1st. The so-calTed Lower Magnesian limestone, which is regarded as theequirarl lent of the Ciilciferous Sandrock, and is from 200 to 260 feet in thickness. Itii| the lead-bearing rock of Missouri, and probably contains the cobalt ores of that regio&l 2d. The Ocdena limestone, consisting of about 260 feet of dolomite interpoaedl between the Trenton and the Hudson River groups. It is the lead-bearing rock ofl Iowa, Wisconsin and Illinois. I 3d. The Niagara limestone, also dolomitic, about 260 feet in thickness, and 8on»l times holding galena and blende. I 4th. The Leelaire or Oalt limestone, a dolomitic formation interposed betveeol the last and the Onondaga Salt Group. It attains upon the Mississippi a thidmMl of 600 feet, but thins out to the eastward. 5th. The magnesian limestones of the Onondaga salt group, 100 feet thick. 6th. A dolomitic deposit in the upper part of the Carboniferous series. The formation No. 1, although generally regarded as the equivalent of the Caldf I erous sandrock, is perhaps the representative of the Chazy limestone, which on L«Im| Huron is sometimes a pure dolomite, and on the islana of Montreal includes tUil magnesian beds. The Oalciferous sandrock itself, throughout Lower Canada, indudeil extensive beds of dolomite, and the Hudson River group is characterized by bedi| of dolomite and of magnesite. and the formation of Oypsum and Magnesian Roch. 23 in thickness, and boh* of recent formation a dolomite from the coral island of Matea, examined by Silliman and myself. — {Am. Journal of Science, [2], |xix,429.) 50. The mechanical conditions of these magnesian limestones I vary greatly; they are sometimes made up of crystalline grains of aolomite, whicn are strongly coherent, or more rarely form a I loose sand. Not unfrequently the magnesian limestones are con- cretionary in their struct-ure, and may be oolitic or botryoidal. I The action of the concreting force has sometimes obliterated the narks of stratification. The porous or cavernous structure of many dolomites is also to be remarked. Magnesian limestones often contain large admixtures of clay jndsand; dolomite is not unfrequently the cement of brecciaa or conglomerates, as in the well-known conglomerate of the Per- mian system in England. Concretionary masses of dolomite sometimes occur in these aggregates, and in the Permian rocks of the Vosges are found in beds of a sandy clay, itself occasion- I ally cemented by dolomite. I I'ave elsewhere described two remarkable dolomitic cou- Iglomerates from the pala30zoic rocks of Canada. The first of these belongs to the upper portion of the Hudson River group, md is conspicuously seen at Pointe Levis and on the island of lOrleans. The associated rocks are there graptolitic shales, sand- Irtones and fossiliferous limestones, together with great masses of I greenish or gravish-white subtra'^slucent compact concretion- lary limestone. This is without distinct marks of stratification, exhibits no trace of organic remains under the microscope, and all the characters of a travertine or calcareous sinter. Intcr- Istratified with this last are beds of bituminous yellow-weather- ing dolomite, containing carbonate of iron, and always intermixed with more or less sand or clay or both ; the clay in one speci- men amounted to fifty per cent, while another quartzose variety mve carbonate of lime 53*04, carbonate of magnesia 31 '96, car- bonate of iron 5'80, silicious sand 8'80=99-60. The latter is a friable crystalline rock, showing in its fracture broad surfaces of cleavage, like the crystals of Fontainebleau sandstone. These dolomites, which contain no fossils, are occasionally traversed by veins of quartz and calcareous spar, or contain small masses of the latter mineral, apparently filling cavities. They are inter- stratified alike with tne travertines and with the fossiliferous limestones, sometimes in large beds, and at other times in lentic- ular masses or in layers of a few lines in thickness separating Imasses of the travertine. The conglomerates of this series inclose in a paste of ferrifer- lous dolomite, grains and rounded fragments of limestone, often having the characters of the associated travertine, together with bgments of quartz and argillite, and small masses of a nearly ' a li I '3"J nl •♦^• pi f If; ' .rr If. '■-.■ ^■^• a 1 11 ^.■'■■f 4 ■ ■;■ ■■ , .1 ^^v MI'-;:;: '■'X I. ^:i':t MP f 1.1" Kl 24 0« some Reactions of the Salts of Lime and Magnesia, pure yellowish crystalline dolomite ; these are perhaps concre- tionary in their origin and not imbedded fragments. Other beds of a similar congiomf rate occur in the same series having a ce- ment of pure carbonate of lime, and the travertine itself often incloses grains of sand. — {Oeol. Surv. Canada; Beport^ 1853-56, p. 465.) The other conglomerate to be noticed occurs on the islands of | Montreal, St. Helens, and several other localities in the neigh- borhood, and belongs to small detached patches of the Lower Helderberg series, left after denudation, which repose uncon- formably alike on Lower Silurian and Laurentian rocks. In some localities they enclose the peculiar feldspars of the latter, in others the fossiliferous limestones, shales, sandstones and cherts of the former series, while in others still the principal ele- ments are black augite, mica and olivine, derived from the igne- ous rocks which in this vicinity have broken through the Lower I Silurian series. These conglomerates, which are remarkable for | their great coherence, have a greenish, bluish or grayish yellow- weathering base, and contain much carbonate of iron. The solu- ble portion of a, specimen from St. Helens was equal to 46"0 per j cent, and consisted of carbonate of lime 57*8, carbonate of mag- nesia 164, carbonate of iron 25'8=100'0. In one instance these! yellow-weathering beds of conglomerate are associated with| others of which the cement remains white on the exposed sur- faces, effervesces freely with acids, and is pure carbonate of lime, j —(76id, 1857, 201.) 51. Dolomite also occurs filling up fissures and cavities inj other rocks, as in the case of pearl-spar in geodes and veins. The blr.ck and yellow marble from northern Italy, known under I the name of Portor, and belonging according to Savi, to the I Neocoraian formation, is composed, by my analysis, of a black, [ nearly pure limestone containing only one-hundredth of carbon- ate of magnesia, penetrated by veins of ferriferous dolomite, j which gave me 35*5 p. c. of carbonate of magnesia, and 46 ofl insoluble silicious matter, the residue being carbonate of limef and a little carbonate of iron. The veins of magnesian carbon- [ ate sometimes give to the Portor the aspect of a breccia. 52. Examples of the apparent infiltration of dolomite ocCutI in black bituminous limestones at Montreal and Ottawa belong-F ing both to the Trenton and Chazy divisions. These limestones, which contain only traces of magnesia, enclose casts of the inj terior of Orthocerns, Murchisonia and Pkurotomaria, consisting ofl a gray crystalline dolomite, weathering reddish, and appearing j in high relief upon exposed surfaces of the limestone. In bothj localities the limestones are traversed by thin irregular veins ofl a similar dolomite, which communicate with the casts. By the! action of dilute hydrochloric acid the limestone matrix is dis-l and the formation of Gypsum and Magnesian Rocks, 25 n the islands of jsin theneigU- ;3 of the Lower repose uncon- .tian rocks. In 3 of the latter, in tones and cherts ^e principal ele- ,d from the igne- rough the Lower ■e reiparkable for r grayish yellow- • iron. The sok- equal to 46-0 per jarbonate of mag- ! me instance these i I associated witlil the exposed sur- carbonate of lime. I bne j solved, and it is seen that the cavity of the fossil is in manj cases only partially occupied by dolomite ; that portion which is uppermost in the stratum being often filled ■^ith carbonate of lime to the extent of one-third or one-fourth, but in other speci- hnens the whole cast is of dolomite. In some of the larger casts tkere are drusy cavities lined with crystallized dolomite and oc- casionally containing prisms of quartz. The analysis of a frag- ment of the cast of an Orthoceras from the Trenton limestone at Ottawa, gave me carbonate of lime 56'00, carbonate of magnesia hl'SO, carbonate of iron 5'95=99*75. The surrounding lime- lsto"e, which was compact, bluish-gray, and bituminous, con- Itained 3*9 p. c, of clay and sand; its solution ^ave 0*6 p. c. of loxyd of iron with alumina, but no magnesia. Similar examples of fossils replaced by dolomite occur in gray limestones associa- ted with the travertines and dolomites of Pointe Levis (§ 50). 53. Magnesian limestones are very frequently destitute of or- ganic remains ; in some cases however they may contain calca- jieous fossils, as in the Niagara limestone at Dudswell, where Lrals of the genera Cyathophyllum, Ponies and Favosites, com- Ijosed of pure carbonate of lime, and generally bluish-black in lor, are imbedded in a yellow ferriferous magnesian limestone ikich contains an excess of carbonate of lime. This limestone ,ve by analysis carbonate of lime 56'60, carbonate of magne- ill*76, carbonate of iron 8*23, insoluble quartz sand 26*72= l5'31. The portion soluble in cold dilute acetic acid was car- mate of lime with four per cent of carbonate of magnesia and trace of iron, and the residue when digested with dilute hydro- "oric acid left 52*0 p. c. of sand '■ind pyrites ; the dissolved consisting of carbonate of lime 51 "75, cavbonate of magne- ia 35-73, carbonate of iron 12-52= 100-00. In the magnesian limestone of Gait in western Canada, which a pure crystalline dolomite, there are numerous casts of bi- ve molluscs, the shells of which were evidently removed by Won after they had been filled and enveloped by the dolo- itic matrix, since the walls of the cavities once occupied by le shells of a large bivalve, Megahmus Canadensis, retain the kings of the inner and outer surf{> ses of the shell. Similar loulds of Ophileta compacta are abundant in the blue dolomite ^Beauharnois, which belongs to the Calciferous sandrock; in dolomite of the same geoloj^cal formation from the Miugan nds, the shells of Ophileta, MacJurea and Scaphites are re- iced by silica. In some portions of tne Gait formation fragments of encrinal ilumns are found replaced bv dolomite, which is only distin- lislied by a little difference oi color from the matrix. It would ipear in this case as if the calcareous fossil having been first imoved by solution (§30) the cavity had been suldcquently SECOND SEKIB9, Vol. XXVUI, No. 84.-NOV., 18S9. 25 > ^ 26 On some Relations of the Salts of Lime and Magnesia, riii t- 'M- Ml «» .* •■ i ■•.. -.1 ■' V ■f .<-••' t i "f I- ■■f m 4rv filled with dolomite as in the casts found in the Ottawa and I Montreal limestones (§ 52). 54. Although dolomites not unfrequently form by themselves I masses of great thickness, as in the Jurassic formation of tlel Tyrol and the palaeozoic rocks of the west, they are often inter- [ stratified in an intimate manner with pure limestones. Such ial the case with the ferriferous dolomites already noticed in describ-l ing the dolomitic conglomerates and travertines of Pointe LevisI (§ 50). In the Chazy limestone of Montreal, thin irregular layerel of reddish ferriferous dolomite, themselves filled with encrinall columns, are interposed between beds of fossiliferous limestone.! The magnesian layers being pulverulent, the encrinal columns I which are pure carbonate of lime, are easily separated from theirl matrix, which gave me carbonate of lime 40"95, carbonate off magnesia 2419, carbonate of iron 27"03, silicious sand without! alumina 9*01= lOl'lS; the iron was in part as peroxyd. Thei bluish crystalline limestone distant an inch from the magnesian layer gave 184 p. c. of white insoluble residue and 1*09 p. c. ofl carbonate of ipagnesia. In these strata we sometimes meet with similar reddish pulJ verulent layers which contain no carbonate of magnesia, but are composed of carbonate of lime with a large amount of peroxya of iron ; such a mixture in one instance forms the cement of ( breccia of fragments of the blue limestone ; it was perha one time a double carbonate of lime and iron. The thin beds of dolomite above described are closely i ciated with those holding the dolomitic casts of orthoceratite already noticed ; these were enclosed in a nearly black compai limestone, which during its solution in hydrochloric ac' d evolvei traces of sulphuretted hydrogen. The residue contained a iittlil iron pyrites which was removed by nitric acid ; it was blacH from carbonaceous matter, but became white by ignition in tlij air, and was an impalpable powder, equal to 12*8 p. c. of M rock. Dilute soda ley removed from it 9*5 p. c. of its weight c soluble silica, and the residue had nearly the composition of i feldspar. It gave me, silica 73'02, alumina 18"31, lime 0'93l magnesia 0'87, potash 5 55, soda 0*89 =99*57. The fossiliferous yellow magnesian limestones of Dudswel (§ 53) are in like manner interstratified with beds of gray crji tallina limestone containing 6"3 p. c. of sand and only l"3p. of carbonate of magnesia. These beds having been much di^ turbed and broken, the interstices appear to have been up with portions of the yellow magnesian paste giving rise tol marble which in some portions resembles the so-called Portoij (§51). 55. We see from the above examples that dolomites may ( cur interstratified both with limestones of organic origin anl and the formation of Gypsum and Magnesian Rocks. 27 the Ottawa and! with others which are evidently chemical deposits. Allied to these latter are certain porous tufaceous beds of carbonate of lime which sometimes accompany dolomite. Such tufas occur alternating with the dolomites and gypsiferous marls of the Onondaga salt group, A similar layer of cellular calcareous tufa, free from magnesia, I have observed immediately covering a deposit of crystalline incoherent dolomite in the Eocene scries I at Pont St. Maxence in France. — (See also Damour, Bull. Soc, Ghl de France, [2], xiii, 67.) 56. The chemical constitution of the rocks containing carbon- te of magnesia now demands our consideration. Pure dolomite I is well known to consist of equivalents of carbonate of lime and I magnesia corresponding to 45*65 parts of the one to 54'85 of the I other, and many magnesian limestones have this composition, or I contain beside only mechanical impurities, such as sand and clay. Others with an excess of carbonate of lime are shown by the method of Karsten to be mixtures of dolomite with carbon- ate of lime, which is readily separated by the solvent action of told dilute acetic acid (§ 28, § 53). The same chemist however Ifound in clefts and fissures of the gypsiferous rooks of Luneberff lied elsewhere, carbonates of lime and magnesia mingled with from which dilute acetic or muriatic acid removed the [ihole of the lime, leaving a residue of from 4*0 to 68'0 p. c. of magnesian carbonate which had evidently been mechanically in- termingled with the carbonate of lime. (Bischof, Lehrhvm, ii, 1161.) Since the presence of sulphate of lime appears to pre- sent in a great measure the union of the two carbonates (§ 81), b might suppose that the association of gypsum with these agnesian clays had in some way hindered the formation of the louble carbonate. The free carbonate of lime which they con- is however probably epigenic and produced by the decom- ition of a portion of the magnesite by the infiltration of dis- ilved gypsum. Carbonate of iron often replaces a part of the magnesian car- mte in dolomites, which also sometimes contain carbonate of ngauese, and even carbonates of zinc, cobalt and lead. It lot unfrequently happens that the sum of the other carbonates these ferruginous dolomites is more than equivalent to the bonate of lime. Such is the case with the dolomitio conglom- ,te of St. Helens (§ 50). The dolomites of the Hudson River group in eastern Canada very often associated with copper, nickel, titanium, chrome d manganese. A grayish granular dolomite from Sutton, hich contains disseminated chlorite and crystals of magnetite, eathers blackish-brown from the presence of manganese. The reign minerals are arranged in bands, and layers of the dolo- te an inch or two in thickness are apparently free from ad- '■ M 11 M- '.-,'",. I. ,-. •. I. J i . ' r ' r ^■•'.*- ■ I', . ■ • f n 28 On some Relations of the Salts of Lime and Magnesia, mixture. The analysis of such a portion gave me, carbonate of I lime 4010, carbonate of magnesia 20*20, carbonate of iron 1065 1 carbonate of manganese 7*65, insoluble, chiefly quartz, 21*45=1 10000. The associated crystals of magnetite contained no trace! of manganese.* 57. Magnesian limestones containing an excess of carbonate! of magnesia are not uncommon ; one from the muschelkaJk off Thuringia gave to Senft, carbonate of lime 42*9, carbonate ofl magnesia 55*4, besides 2*7 of carbonate of iron =101*0. Ala-I custrine dolomite from the brown-coal formation near Giessenl contains, according to Knapp, carbonate of lime 42*80, carbonat< of magnesia 49*63, besides oxyd of iron and impurities, and i specimen from the Lower Magnesian limestone from Lake SupeJ rior gave to Whitney, carbonate of lime 25*28, and carbonate on magnesia 32*57, besides 37*0 of sand and a little iron and alumina! Similar magnesian rocks are described by Alberti as occurriD/ in the variegated marls of the keuper or upper part of the TriJ assic system in Germany. A tender greenish schistose marl from Tubingen effervesced very slightly with acids, and gavl for 100*00 parts, carbonate of lime 14*56, carbonate of magnesij 19*10, the remainder being clay with a little iron-oxyd. (Senfl Die Fekarten, 184.) Von Bibra has described similar magnesia^ marls from the muschelkalk in Franconia (Bischof, Lehrbuch, i 1158), and Gueymard from the gypsums of Eoquevaire in Pr vence. The bituminous salt-clays {salzthon) which occur ffit| gypsum and rock salt, when freed by washing from soluble salts contain according to Schafhautl, carbonates of magnesia and iroj often with very little carbonate of lime, the argillaceous matb varying from 12*0 to 70*0 p. c. (Bischof, Lehrbuch, ii, 1725J To these clays are perhaps related the magnesian marls examinef by Karsten (§ 56). Volckel has described a dark gray rock iij * Carbonate of manganese is frequently met with in the rocks of this geolo[ series, causing them to weather brownish-black. I have described an impure c ritic limestone of this kind from Granby (Canada East), which contains besides p oxyds of manganese and iron, portions of chrome, nickel and titanium. (Rep 1853-56, 474, and this Journal, [2], xxvi, 238.) Rogers has in like mannemoticj the occurrence of a large proportion of protoxyd of manganese in the olive colorj slates of the Lower Silurian series in Pennsylvania, and to the decompoeitioDl such rocks correctly ascribes the origin of the deposits of peroxyd of manguiel met with in that region. Beds of silicate of manganese, more or less interminglj with carbonateij of manganese and lime, are interstratiiied with crystalline scbi in various localities in New England. I may mention in th's connection a eom{M massive carbonate of manganese which is said to occur in slates supposed to wj Silurian age, at Placentia Bay, Newfoundland, and which I received from Dr, J. Dawson. It is conchoidal in fracture, translucent on the edges, with a feeble n lustre; color fawn to pale chestnut-brown. H. 4'0. D. 3'25. It is penetrated a incrusted in part with crystalline peroxyd of manganese. Acids in the cold scare attack this mineral, but heated nitric acid dissolves it with effervescence, leaviiij residue of 14*4 p. c. of silica, of which the greater part is soluble in a dilute al line solution. The analysis gave me besides 84'6 p. c. of carbonate of moDgaDij and traces of lime, iron and magnesia. (Report, 1867, 204.) Blind om th nalysis pes, anc pves ar we air rod ome. fesce wi lives tl BDiaine Nish-I "TTI I Magnesia, carbonate ofl te of ironlO-65,f le, quartz. 21-45= intained no trace! ess of carbonate] I muschelkalk of 5-9, carbonate of! t =101-0, Ala-I ion near Giessei 3 42-80, carbonat/ impnrities, andi from Lake Supe] and carbonate on iron and alumina] berti as occumDo r part of the Tnj sh scbistose marl 1 acids, and gm (onate of magnesij [•on-oxyd. (Senf similar magnesiaj Lschof, Lehrhmk' aoquevaire in Pi ■which occur wit] from soluble salts magnesia and iroj argillaceous mad Lehrhuch, ii, 1725| ian marls examine dark gray rock iii e rocks of this geologic lescribed an impure ct- lich contains besides p and titanium. (Re[ as in like manner note anese in the olive coloi to the decomposition! -if peroxyd of man^ more or less interming) sd with crystalline scb- th^s connection a comi, slates supposed to be J. received from Dr. J. Udires, with a feeble^ •25. It is penetrated I Acids in the cold scar h effervescence, leavu ■ soluble in a dilute^; carbonate of ma" |)4.) and the formation of Gypsum and Magnesian Rocks, 20 terstratified with limestone from the Jceuper near Solothum, and consisting of carbonate of magnesia 54-55, carbonate of iron |33'94, carbonate of lime 0*67, with 10'81 of clay, water, etc. (i. and K. Jahreshericht, 1849, 581.) 58. Magnesian rocks allied to the last occur in the Hudson [River group of eastern Canada, and were described by me sev- ' years since. In the township of Sutton, interstratified with [dolomite, steatite and talco-quartzose strata, is a bed of green and white reddish- weathering crystalline rock, gneissoid in struc- ture, and containing variable porportions of magnesian carbon- ate. A pure and nearly white fragment gave to hydrochloric acid, carbonate of magnesia 83-35, carbonate of iron 9-02, and left insoluble 8-03=100-40; while another specimen from the jame mass contained, carbonate of magnesia 33-00, carbonate of iron 19-35, alumina 0-50, insoluble 45-90=9870. In both cases [the solution contained a little nickel, which occurs in the rock, part at least, in the form of grains of nickeliferous pyrites, le insoluble portion is a silicate of alumina and alkalies, with little magnesia, and appears to consist of a mixture of feldspar ith. a little mica and talc, the latter minerals being colored em- Id-green by a small portion of oxyd of chrome. In the township of Bolton there occurs a bed of magr jsite ly yards in breadth, interstratified between steatite c i the le side, and an impure ophiolite passing into diorite, on the ler. It is made up of brilliant cleavable grains of magnesian ', bluish-gray or nearly white in color, and intermingled with lers of white hyaline quartz, which sometimes forms small igular veins. One of several analyses of this rock gave me, rbonate of magnesia 59-13, carbonate of iron 8-32, insoluble •20=99-65. In other specimens the proportion of carbonate iron is a little greater, and traces of carbonate of lime are metimes met with, while nickel is never wanting and sometimes )ats the joints of the rock with a yellowish-green film of what _)prs to be a hydrocarbonate of nickel ; the proportion of this letal determined upon a considerable quantity of the rock was )und equal to about one-thousandth. The insoluble residue )m this magnesite was greenish-gray in color, and gave by lalysis 93'6 p. c. of silica, besides some alumina, 0*8 of alka- [ies, and traces of lime, magnesia, and oxyd of chrome, which ives an emerald-green color to some portions of the rock. I lave already shown that nickel is rarely absent from the magne- rocks of this region, where it is generally accompanied by ime. These magnesites in powder do not perceptibly effer- le with cold hydrochloric acid, which however readily dis- ives them with the aid of heat. The decomposition of the iniained carbonate of iron renders their weathered surfaces iidish-brown and pulverulent. — {Eq)ort, 1853-56, p. 460.) '^1; It i' i."''r. -V. IV.^•^ , ■?■■ 4 ■> ■ i w \ t'*- i .■ i.; n . ■;'! V ^,4 ;:■■: '. ^;.K I.* dA 't ■ i\ M ■ i mm \ .' •;• '■ Jf i;'lVvU:.::'i ! . !' ■ ". it 30 On some Relations of the Salts of Lime and Magnesia, I have detected a quartzose magnesite closely resembling tl of Bolton, containing nickel, and stained emerald-green by oxjJ of chrome, among a collection of rocks brought from CalifornJ by Mr. W. P. Blake, who also found a bed of nearly pure whit] compact carbonate of magnesia amon^ the crystalline schists d that region. I may here recall the existence of beds of magnej site among argillites in Styria, and also in the ancient crystallinj gneiss of Modum in Norway, where a crystalline magnesite i the gangue of crystals of serpentine and ilmenite. — {Am. i/^i of Science, [2], v, 389.) 69. The greater number of dolomites and magnesian roci] are shown by their fossils or by the nature of the associatf strata to be of marine origin, but dolomites are also found I fresh-water deposits. Such is that with excess of magnesia] carbonate from the brown-coal formation near Giessen (goJJ and dolomites are said to occur with the lacustrine limestones c Dachingon near Ulm. — (Senft, Die Fekarten, 133.) On the mode of formation of the preceding rocks. 60. Having in the fourth division of this paper brought ' gether the principal facts in the history of magnesian rocks, i well from the researches of others as from our own observation! we have seen that these rocks consist essentially of dolomiti mixed with carbonate of lime on the one hand, and with carboj ates of magnesia and iron on the other, passing thus into magnl site. The frequent intermixtures of sand and clay and evenf fragments of quartzite, argillite and limestone, clearly their sedimentary origin, which is moreover rendered evideJ by the fact that they are often interstratified with pure lin stones and even inclose calcareous corals; these facts excluJ the idea of the formation of all such dolomites at least, by tlj alteration of deposits of carbonate of lime as supposed by Va Buch, Haidinger and Favre. 61. The dolomites of the Tyrol which Von Buch imagined j have been formed from the alteration of limestones by magn sian vapors evolved at the time of the ejection of certain mell phyres of that region, have been shown to be much more recel than these melaphy res, which according to Fournet are not i trusive but sedimentary rocks, probably of Carboniferous altered in situ. These metamorphosed strata are separated fro! the dolomites, which are Jurassic, by unaltered Triassic straj including the muschelkalk and a conglomerate holding rollj fragments of the melaphyres.* {Bull. /Sac. Oeol. de France^ [I 1 * Bischof cites Fournet, Histoire de la Dolomie, 1847, but I have not been i| to consult the work in the preparation of this paper. tl Masnesia ■ ^''^^ the formation of Gypsum and Magnesian Rocks. 31 f resembling tliai Id-green by oxyj it from Califora nearly pure whitj ^stalline schists c )f beds of magnd ancient crystalling nine magnesitei jnite. — {Am, Join magnesian rock 5 of the associatf are also found :cess of magnesiaj Bar Giessen (§5T strine limestones ( 133.) , ani with carboi ig thus into magnj d clay and even itone, clearly shol ;r rendered evidei ed with pure lii these facts exclai lites at least, by tl s supposed by V( 1 506-616.) In several other cases where dolomization was Uposed to have been produced by the proximity of igneous bcks, Delesse and Delanoue have shown that the change had |een limited to an alteration in the texture, and that there had m no addition of magnesia. 1 62. Favre supposes with Haidinger that magnesian solutions pder heat and pressure have given rise to dolomites by decom- aing beds of limestone with formation of carbonate of magne- , agreeably to the observations of Von Morlot and Marignac. lid., [2], vi, 318.) This hypothesis is evidently not applicable f those magnesian limestones which include beds, fragment's or ganic remains of pure carbonate of lime. In any case we lust suppose a long continued filtration of solutions of magne- V chlorid through the heated limestone under certain condi- m which seem at least improbable. 1 63. The theory of the formation of magnesian sediments will 1 readily understood from the experiments which have been bribed in the earlier parts of this paper, but before proceeding I its consideration I wish to call attention to the results of the Jocentration by evaporation of natural waters in basins with- it an outlet. If such a basin contain sea- water, the gypsum, ng insoluble in a saturated brine, will be entirely deposited fere the crystallization of the sea-salt, and there will remain quid contaming no lime-salts, but chlorids of sodium and mag- Such are ding rocks. paper brought magnesian rocks, i r own observation ,. .,, , - ♦ o i i * f tiallv of dolomitW"^^ with a large amount or sulphate oi magnesia. - • waters of Lake Elton and many of the brine pools of the ian steppes, while on the contrary the saturated brines of Dead Sea and some other salt lakes contain little sulphate It abundance of chlorid of calcium, and if they are the residues ea-water, have been modified by additions of this salt, which converted the sulphate of magnesia into chlorid of magne- and gypsum, the calcareous chlorid remaining in excess. iut while some of these saline lakes may be supposed to be iins of sea- water, modified by evaporation, either alone or con- ned with the influx of foreign saline matters, others were evi- n Bucb imagined W^ oi^ce fresh- water lakes in which, the loss of water being 1 to the supply, have gradually accumulated the soluble of all the rivers and springs flowing into the lake. We ij arrive at some notion of the diverse natures of the different ine lakes which would be formed in this way if we suppose I waters of different European rivers to be subjected to evap- ition under conditions like those of the salt lakes of Western In the waters of the Elbe and Thames chlorids greatly >rate holding rollWoininate (in the latter with gypsum), with small amounts of 'g'/)1 de France, [Bgnesian salts, and the evaporation of these waters would give ■ to lakes containing a large proportion of common salt. In but I have not been a^ggi^g ^j^ ^j^g contrary, sulphate of lime predominates, while nestones by ma| ion of certain mei e much more rece| Fournet are noti| Carboniferous I are separated fr ered Triassic stial fii 4 ml .1 : ■.'(*■(■■■■• MM ,(■■•'■ •! '.■ : 4 i] l.» .J :, I ' • I J, 1 i:hf'>^ ' !>■' (I, . ■ ' 1 !■■'' ■ •' . >'■ * ■ < ■ i (■■ ■,; • J' ■.- 32 On some Relations of the Salts of Lime and Magnesia, the waters of the Ehine, the Danube, the Arr and the Arv^ contain but small amounts of chlorids and large proportions o| sulphates of lime and magnesia. 64. In other rivers we find alkaline salts ; the Loire at OrleansJ according to Deville, contains in 100,000 parts, 13'46 of soliif matters, of which 35'0 p. c. is carbonate of lime, 300 p. c. silic while two-thirds of the more soluble salts consist of carhonatf of soda. In the waters of the Garonne, with as large a proporl tion of silica, and more carbonate of lime, the carbonate of sodaj equals one-fourth of the soluble salts, while 100,000 parts of th^ water of the Ottawa, according to my analysis, contain 6'11 parts of solid matters, consisting of carbonate of lime 2*48, carbonate of magnesia 0"69, silica 2*06, sulphates and chlorids of potassiu and sodium 0*47, and carbonate of soda 0*41. {Report Geol Sur\ vey of Canada, 1853-56, 360, and Philos. Mag., [4], xiii, 239.) Silica, although more abundant in alkaline river waters, whicll are chiefly derived from crystalline rocks, is not wanting in wai ters containing neutral earthy salts, like the Seine and the Bhonei of the solid matters of which, according to Deville, it forms re] spectively 10*0 and 13*0 p. c. — (Ann. de Chem. et Phys., [31 xxiii, 32.) The waters which rise from the Lower Silurian shales of thJ St. Lawrence valley are, as I have elsewhere shown, remarkablJ for the predominance of alkaline salts, which sometimes amounj to one-thousandth, or more than one-half the solid matters pn ent ; these waters are distinguished from the river waters ju mentioned by their comparatively small amount of silica earthy carbonates, and by the presence of a notable proportionj of borates. — {Bep. Geol. Purvey of Canada, 1852, p. 165,-1853 56, p. 469, and Proc. Royal Soc, Phil. Mag., [4], xvi, 376.) We may here refer to the strongly alkaline waters far^isiiei by the artesian wells of Paris and London as evidences of M abundance of alkaline carbonates in natural waters, andtotlie| springs of Vichy and Carlsbad, the latter of which, accordiE to the calculations of Gilbert, furnish annually more than thirteen millions of pounds of carbonate of soda. The evaporation o| these alkaline v.aters, whether rivers or springs, must givei to natron lakes like Lake Van and those of the plains of Araiei Lower Egypt, and Hungary. — (Bischof, Lehrhuch, ii, 1143.) The carbonate of soda contained in these waters has its i in the decomposition of feldspathic minerals, and shows the ( tinance in our time of a process whose great activity in fonnej geologic ages is attested, as I have elsewhere maintained, byvai accumulations of argillaceous sediments deprived of a large poij tion of their soda, and also by the carbonate of lime which bi the intervention of carbonate of soda has been formed from m chlorid of calcium of the primeval ocean and deposited as limej stone. _ and the formation of Gypsum and Magnesian Rocks. 33 nd Magnesia, ■ B 65. An indispensable condition for the precipitation of car- rr and tne ArveB donate of magnesia is the absence of chlorid of calcium from rge proportions o^ ^^^^ solutions, and this in the presence of excess of sulphates is attained simply by evaporating to the point where gypsum be- comes insoluble. In nearly all river and spring waters bicar- bouate of lime is present in a large proportion, and is often the most abundant salt. We have shown that when mingled with a solution containing sulphate of magnesia, it gives rise by double decomposition to bicarbonate of magnesia and sulphate of lime. „ ,^By the evaporation of such a solution, the latter salt, being the 30,000 parte 01 th«|ggg soluble, is first deposited in the form of gypsum, while the ' contain oil P^J^magrnesian carbonate is only separated after farther evaporation, nae 2'48, carbonattj^l^gj^^ provided the supply of bicarbonate of lime still continues, the two carbonates may fall down in a state of intermixture. 1q this way sediments will be formed containing the elements of dolomite or magnesite. 66. The solution of magnesian carbonate remaining after the jiiepositica of the gypsum, possesses, as we have seen, the power decomposing chlorid of calcium, and when deprived of a irtion of its carbonic acid by evaporation, reacts in a similar lanner with a solution of sulphate of lime (§ 5, § 23). In this ay, an influx of sea-water into the basin from which gypsum, - , , uj^^ perhaps a portion of magnesian carbonate has already been ( shown, remar a ^KpQgite^j^ would give rise to a precipitate of carbonate of lime. 3 Loire at Orleans, ts, 1346 of solii le, 300 p. c. silii insist of carbonal as large a proper' carbonate of sodi lorids of potassi (Bevort Oeol. Sup ^; [4], xiii, m river waters, wmcl not wanting in wa- jine and the Rhoni Deville, it forms rel Jhem. et Phys., [3], lurian shales of tliJ X sometimes amotinl i solid matters p: le river waters j nount of silica m notable proportioi 52, p. 165,-185r [4],xvi,376.), Ine waters fo-.sQi as evidences of till ,1 waters, andtothi .f which, accordini ly more than thirteei e the tufaceous limestones, whose occurrence with gypsum id dolomites has been already noticed. In basins which, like le salt lagoons of Bessarabia on the shores of the Black Sea, eive occasional additions of sea-water, and deposit every sum- ler large amounts of salt, (Bischof, Lehrbuch, ii, 1717,) the influx if waters containing bicarbonate of lime would give rise to the raation of beds of gypsum, alternating with dolomites or lagnesian marls and rock salt. 67. We have already referred to the analyses of certain rivers, which the sulphates are more abundant than the clilorids. us, iu the Rhine, near Bonn, according to Bischof, we have mi tinn n^'^ 100,000 parts of the water, 17*08 of solid matters, of which The evaporation o«,2g^^^ sulphate of lime, I'Sl sulphate of magnesia, with only ings, ?^^ f^j^^io of chlorid and 8-37 of carbonate of lime; in the Danube ,he P^^^^^il^Qv ^Bear Vienna, the predominance of sulphates is still more marked. rbwh, 11, ^ .r^'j^^^^Blie waters of the Arve, in the month of February, gave to Tin- waters has its somu—^^^^^ 100,000 parts, 24-5 of solid matters, of which 6-5 were ,, and shows "^^^Mphate of lime, 6'2 sulphate of magnesia, and 8-3 carbonate of jat ^?*V^. •''^ j'^v.yyj^B'ie, with only 1-5 of chlorids. Now, as in river waters there maintame , y "^Hahy^yg present an excess of carbonic acid, and as bicarbonate lime and sulphate of magnesia in solution are mutually de- imposed, these waters, which are to be regarded as solutions of pliate of lime and bicarbonate of magnesia, (§ 18) would, by EWND SERIES, Vol. XXVIII, No. 84.-NOV., 1859. 36 privedofalargepoH Ite of lime whicli bj feen formed from tij Ind deposited asm n wi i i If [■■<■ a. .1, ' . ,.■.!»■ r '' •*/ n:-*-: ■.;•',*• ■ ..■*.,•; :. ''■■■■'it-* fV ; 4* ^:-: ■■* -'.''. ,.'''' i -f - .. ■;■' r ■ ''» : > ' ■ )■' » It '.-.. 1 ( L. .i ■ * " '■* s , ■ ■ -.''* V f ■ >l . «^' ,.• ( 1 j: ; ■' <,v 34 On some Relations of the Salts nf Lime and Magnesia, their evaporation, yield gypsum and magnesian carbonate, which would appear as portions of a fresh-water formation, like those of Aix and Auvergne. The decomposition of soluble sulphates by bicarbonates of| baryta and strontia, will explain the ibrmation of heavy spar and celestine, and their frequent association with gypsiferous rocks. 68. As to the native sulphur which is often associated bothl with epigenic and sedimentary gypsums, it has doubtless in every case been formed as Breislalc long since indicated, by the decomposition of sulphuretted hydrogen. It is well known that alkaline and earthy sulphates are reduced to sulphurets by organic matters, with tlie aid of heat, or even at ordinaryj temperatures, in presence of water. To the decomposition ol these sulphurets by water and carbonic acid, we are to ascril not only the sulphuretted hydrogen of solfataras, which, by its oxydation under different conditions, gives rise either to fre sulphur, or to sulphuric acid and to gypsum by e^iigenesis, bu^ also the sulphuretted hydrogen which appears in springs and in stagnant waters, where the sulphur produced by the decomposij tion of the gas is often mingled with sedimentary gypsums, (See Bischof, Lehrbuch, ii, 139-185.) This author has suggested the decomposition of chlorid of magnesium by alkaline or earth] sulphurets as a source of sulphuretted hydrogen and hydrate magnesia, into which sulphuret of magnesium is readily resolve in the presence of water. {Chem. Geology, i, 16.) If a salt calcium were present, this reaction could only take place in thj absence of carbonic acid, for carbonate of magnesia is incoi patible with chlorid of calcium. The direct reduction anj decomposition of sulphate of magnesia by organic matter anj car jonic acid may, however, yield sulphuretted hydrogen magnesia, and thus, in certain cases, give rise carbonate of magnesian sediments. 69. In the preceding sections, we have supposed the wateij mingling with the solution of sulphate of magnesia to conta; no other bicarbonate than that of lime, but bicarbonate of so is often present in large proportion in natural waters, and U addition of this salt to sea-water or other solutions containiii| chlorids and sulphates of lime and magnesia, Avill, as we seen, (§ 1) separate the lime as bicarbonate, and give risei liquids, which, without being concentrated brines as in tlj previous case, will contain sulphate of magnesia, but no h salts. A farther portion of bicarbonate of soda will produj bicarbonate of magnesia, by the evaporation of whose solutiol as before, hydrated carbonate of magnesia would be depositef mingled with the carbonate of lime which accompanies the m * On certain modes of decomposition of the sulphates, see Jacquemin, Cotnji Rendus, June 14, 1858. ms' ftates ilbai literv ligin fpsu: l^ian ;iy : Inub Bllld in. )nate frtain foss imesto Itemic Ire of Fkich The IPpears I even f e crvs Uof bunion lliich ii }nof filion f( ne ch ise We Uidstone pier ari( ? riiiii; iTIiuse W of t AePa as and the formation of Gypsum and Maffnesian Rocks. 35 line salt, and in the case of the waters of alkaline springs, the Icompounds of iron, manganese, zinc, nickel, lead, copper, arsenic, Itlirome, and other metals, which springs of this kind Btill bring l»tho surface. In this way the metalliferous character of many liolomitea is explained, as also the frequent association of metals, Isuch as copper, nickel, cobalt, chrome and titanium, with ser- Lntinc, steatite, diallage, olivine, and other magnesian silicates, lihieh owe their origin to the alteration of magnesian sediments liiich as we have described. 70. As the separation of magnesian carbonate from saline wa- iters by the action of bicarbonate of soda does not suppose a very pat degree of concentration, we may conceive this process to Ijo on in basins where animal life exists, and thus explain the Irigiu of fossiliferous magnesian limestones like those of the kli^well (§ 53,) and the Silurian rocks of the western United ftates, whose fossils, as I am informed by Mr. James Hall of Albany, are generally such as indicate a shallow sea. To the Intervention of carbonate of soda is I conceive to be referred the figin of all those dolomites which are not accompanied by jpsums, and which make up by far the larger part of the mag- psian limestones ; nor will the clolomites thus derived be neces- irily marine, for the same reagent with waters like those of the Inube and Arve would give rise to dolomites and magnesites Vresh-water formations, which unlike those mentioned in § 67, paid not be accompanied by gypsums. "1. To the lirst stage of the reaction between alkaline bicar- lonates and sea water I am disposed to ascribe the formation of jtrtain deposits of carbonate of lime which although included 1 fossiliferous formations, are unlike most of their associated tmestones, not of organic origin, but have the characters of a lliemical precipitate of nearly pure carbonate of lime, in which Ire often imbedded silicified shells and corals.* It is not per- easy in all cases to distinguish between such precipitates, Irliich may assume a concretionary structure, (see on this ques- ' The large proportion of dissolved silica ■wliich mnny river waters contain (§ 64) bpcars in sedimentary deposits, not only replacing fossils and forming concretions BO even beds of flint, chert and jasptr, br;t also in a crystalline state, as is seen in le crvstiillized quartz often associated with these amorphous varieties, and in some fJsof sandstone wiiich are made np entirely of small crystals of quartz. Elie de pumnnt long since called attention to the crystalline nature of certain sandstones pch iis Daubree has remarked, could not have been derived from the disintegra- pof any known rock, and Mr. J Bruinard at tlie meeting of the American Asso- ption fur the Advancement of Science, held at Cleveland, insisted upon the crys- "ine character of the grains composing sandstones in Ohio, as evidence that lesewere chemical deposits. He however fell into the error of supposing that all mljtones and even quartzose conglomerates have hiid a like origin, while the Itteriiml the f;reater part of the former are undimbtedly nieehanical deposits from pniinsof preexisting quartzose and granitic rocks. iTIiu^e crystallized sands according to Daubri'ie, are met with in beds in the sand- pnetif the Vosges, the variegated sandstone (Triassicand Permian,) in the I'rtiary I the Paris basin and elsewhere. Other sands arc made up of glob\iles of calcu- !:: < k^ i 4 36 On some Kelationa of the Salts of Lime and Magnesia, ■A-'i. hX Wt.iJ tion Bischof, Chem. Oeology^ i. 428,) and those deposits wlrcli like travertines have been formed from subterranean springs. In neither case however, should they be confounded with the i tufaceous limestones mentioned in § 63. 72. The union of the mingled carbonates of lime and magne- 1 sia to form dolomite, is attended with contraction, which in case the sediment was already somewhat consolidated, would give rise to fissures and cavities in the mass. Should the dolomitic strata be afterwards exposed to the action of infiltrating carbonated waters, the excess of carbonate of lime and any calcareous fossils | would be removed, (§ 30,) leaving the mass still more porouj", with only the moulds of the fossils. Insoluble however as it I appears to be at ordinary temperatures, the filling up of such cavities both in magnesian and in pure limestones, not less than its deposition in veins and druses, indicates that dolomite is I under certain conditions soluble. The lowest temperature at which hydrous magnesian sedi- ments may be transformed into magnesite and dolomite has yet I to be determined. The requisite neat has however doubtless been attained * by the accumulation of overlying sediments, in virtue of that law which causes the temperature to increase as we penetrate the earth's crust. This increase we may suppose with Mr. Hopkins to have been much more rapid m former | epochs than at present. — {Oeol Journal, viii, 59, also Phillip's Mambal of Geology, 609.) Conclusions. 1. The action of solutions of bicarbonate of soda upon seal water separates in the first place the whole of the lime in tlie| forrii of carbonate, and then gives rise to a solution of bicarbon- ate of magnesia, which by evaporation deposits hydrous mag-| nesian carbonate. 2. The addition of solutions of bicarbonate of lime to sulphate! of soda or sulphate of magnesia gives rise to bicarbonates off these bases, together with sulphate of lime, which latter maybel thrown down by alcohol. By the evaporav.on of a solution con-f taining bicarbonate of magnesia and si?lphate of lime, either! with or without sea salt, gypsum and hvdrous carbonate of mag-| nesia are successively deposited. dony, apparently like the crystallized sands a chemical deposit, and associated viihl oolitic iron ores in the lias, and with glauconite grains in the green-aand. (Daubml Recherches aur le Striage det Rochet, etc., Ann. des Mines 1857, 6 livr.) We may I here mention the no-called gaize from the green sand of the Ardennes, which gave tol Sauvage 66'0 p. c. of amorphous soluble silica mixed with quartz sand and glauco I nite. (Bischof, X«Ar6M