ginning on the west and proceeding to the east, we crossed the Alps successively in the valley of the Rhine, in the Voralberg, in the Allgau, along the Lech, between Fussen and Nassereit; between Seefeldt and Amergau; between Seefeldt and Benedictbeuren; along the Inn, to the southern Tyrol over the Brenner; partly to the south of the Chiemsee lake, in the valley of the Bavarian Traun, of the Saal, and the Achenbach; along the Salza from Salzburg to Werfen; from Salzburg to Liezen; from that place to St Gallen; from Steyer to Eisenerz; from Waidhofen to Eisenerz; from Gaming by Neuhaus, Palfau, and Gams, to Eisenerz; from Neuhaus to Mariazell; from St Polten to Seewiesen by Maviazell; from St Polten to Baden and Vienna; and from Vienna to Gratz and to Croatia, through the Matzegebirge. The collections of rocks made at all these and the following localities I have preserved, and will be delighted to explain them to geologists.

In the southern Alps, we have visited in the same way all the southern border of the calcareous alpine chain from Bergamo to Conegliano. We have ascended along the valleys of the Brenta, seen those of Fassa, of the Cordevole, of the Piave, of the Fella, and of the Drave. Lastly, we crossed the Leoben; we visited Bleiberg, Raibel, Laibach, Idria, the valley between Idria and Lack, Trieste, and Fiume. We went over the greatest part of Istria to its southern termination. We entered into Dalmatia, crossed the Capellen-Gebirge from Buccari to Carlstadt, and, after an excursion farther east, we followed the road from that town to Laibach. We may add, that, well informed of all the difficulties in classifying the Gossau deposite, we last year made a journey through the Austrian Alps, for the sole purpose of studying thoroughly all the well known localities where such rocks occur, and of establishing a reasonable classification, and describing each locality. After these journeys, continued during nine years, for the study of the alpine limestone chain in Germany, we thought that we might, assisted by our friends, attempt to lay before the geological public the conclusions explained in this paper and elsewhere. In what relates to the difference of our opinion from that of Messrs Sedgwick and Murchison, the public will now be able to judge; and, we trust, that they will ere long favour us with an answer, written with that calmness and spirit of concord which ought always to accompany scientific discussions.

On the Chemical Constitution of Brewsterite. By ARTHUR CONNELL, Esq. F. R. S. E. Communicated by the Author.

THIS mineral was first characterized, from its crystalline form, as a distinct species by Mr Brooke, who also gave it its present name *

It would appear that, some years ago, a specimen of the mineral was sent by Dr Brewster to Berzelius, for the purpose of being analyzed; and that Berzelius wrote back in answer, that it had been already analyzed by Retzius, conformably to the formula S3 + 4 A S3 + 8 Aq, and called by him Prehniti

с

N

form Stilbite +. This formula, or the corresponding chemical one, has been retained by Berzelius‡; and I am not aware that any other statement respecting the constitution of the mineral has been given to the public. The locality of the mineral anaIyzed by Retzius is not stated. The formula of Berzelius gives §,

In a former notice on this subject ||, I shewed, from an examination of some pure crystals of Brewsterite from Strontian in Argyllshire, that it contained strontia and baryta, and no notable quantity of lime. I also shewed that it contained no alkali, and concluded that the formula of Berzelius did not apply to the mineral, at least when derived from the above locality, unless the formula and composition could be accommodated to one another by the aid of the doctrine of replacement.

It became a matter of some interest to establish by a regular

Die Anwendung des Löthrohrs, 2te Auf. S. 168.

§ This calculation is made by the atomic weights of Berzelius. All the subsequent calculations of formulæ are made by those of Dr Thomson. || Edinb. New Phil. Jour. No. 16. p. 355.

analysis that the strontia occurs in the mineral as a silicate, and in such quantity as to constitute an essential constituent; because that earth had not hitherto been found in nature, except as a sulphate, or carbonate *.

The specimen of Brewsterite which was the subject of the following researches, consisted of a kind of concretion of the mineral, partly in crystals, and partly in an amorphous state. Previous to analysis, it was submitted, in the condition of fragments, to the action of water, acidulated with muriatic acid, for the purpose of removing any soluble foreign matter.

25.15 grains of the mineral, in the state of fragments, lost, by ignition, in a platinum crucible, and charcoal fire, 3·16 grains, equivalent to 12 584 per cent.

48.34 grains, in impalpable powder, were fused over the spirit lamp, with about three times their weight of a mixture of 5 parts of carbonate of potassa and 4 parts of carbonate of soda, care being taken to employ carbonates free from any sulphate. The mass, after being softened by water, was dissolved in dilute muriatic acid, and the silica separated in the usual manner. The silica, after being ignited and weighed, was dissolved in boiling potash-ley, and left a little residue, which appeared to be undecomposed mineral, and was subtracted from the quantity under analysis.

The residual solution, separated from the silica, was precipitated by ammonia. From the precipitate thus obtained, a little silica and oxide of iron were separated by the agency of muriatic acid, and subsequently of caustic potash in excess. A quantity of alumina was then got, by supersaturating the alkaline solution with muriatic acid, and precipitating by carbonate of ammonia. The alumina was ignited, and weighed.

The liquid which had been precipitated by ammonia was concentrated by evaporation, and carbonate of ammonia was added to it whilst hot. A white precipitate fell, which, after being collected and washed, was dissolved in dilute nitric acid. The solution by evaporation gave a crystalline residue, showing

Baryta, besides occurring in its usual natural states, and as a silicate in some varieties of harmotome, occurs apparently in combination with oxide of manganese in some of the ores of that metal, as has been shewn by Klaproth and Dr Turner.

chiefly small octahedrons, and mixed with some deliquescen

matter.

The deliquescent matter was taken up by alcohol, which left the crystals undissolved. The alcoholic solution was decanted, and converted to a watery solution, to which oxalate of ammonia was added. A white precipitate fell, and the whole was evaporated to dryness. The dry mass was then ignited, a little solution of carbonate of ammonia added, and heat again applied. Some carbonate of lime was thus got, having a trace of iron.

The nitric crystals left by the alcohol were now ignited in a silver crucible, to drive off the acid. The caustic residue was dissolved in very dilute muriatic acid. The muriatic solution was evaporated to dryness, and the dry mass ignited, and weighed. Redissolved in water, a little residue was left, the weight of which was subtracted from the ignited mass. The solution by evaporation gave a mixture of long prismatic, and tabular crystals, having all the appearance of muriate of strontia and muriate of baryta. The former were taken up by hot alcohol, to which a few drops of muriatic acid were added. The latter were left undissolved; and after being separated from the alcoholic solution, and washed with alcohol, were ignited and weighed, and their weight subtracted from the joint weights of the ignited chlorides, by which means the amount of the chloride of strontium was determined. The amount of the chlorides gave by computation that of the strontia and baryta respective ly. From the small quantity of matter left undissolved on the solution of the chlorides in water, after their joint ignition, a little silica, and also a little carbonate of strontia, were separated, which were both duly taken into account.

On recrystallizing the chlorides from watery solutions, the salts obtained had the crystalline form, and all the properties of muriate of strontia and muriate of baryta. The former gave to flame a fine red colour, and the latter a slight greenish tinge. The solution of both afforded white precipitates with sulphuric acid.

Another analysis of 47.37 grains of the mineral was executed in a manner not materially differing from the preceding process, the principal distinction being, that the proportions of the alka

line earths were determined on a separate quantity of the mineral of 25.62 grains, a portion of them from the original quantity having been accidentally lost.

The manner in which the analytic process was conducted afforded sufficient evidence that the alkaline earths did not exist in the mineral in combination with sulphuric acid. But to ascertain with still greater precision whether the mineral contained any traces of sulphates, a little of it, in powder, was fused with carbonated alkalis, the mass treated with hot water, the solution deprived of silica and alumina by carbonate of ammonia, and saturated with muriatic acid. No precipitate was then got with muriate of baryta.

On treating a similar solution, to which ammonia had been added, to take off the excess of muriatic acid, with muriate of lime, and keeping it for a few days in a close vessel, some precipitate which had formed seemed to be carbonate of lime, with traces perhaps of silica or alumina. There was thus no evidence of phosphoric or fluoric acids.

To ascertain whether the mineral contained any alkali, 33·11 grains in fine powder were strongly ignited with six times their weight of carbonate of baryta. The usual steps were taken to separate silica; and the earthy contents of the muriatic solution were thrown down by carbonate of ammonia, its action being aided by heat; the whole evaporated to dryness; the residue repeatedly redissolved; and new additions made of carbonate of ammonia. The muriate of ammonia was then driven off by heat. No trace of an alkaline chloride could be found.

The two analyses which have been mentioned corresponded perfectly with one another, in respect of the nature of the constituents of the mineral; and, although in the one, some loss, and in the other, some excess, was got *, yet they did not differ essentially in the proportions of the constituents in relation to one another. By taking a mean of the two analyses, the excess

* The excess was, I believe, owing to the circumstance, that, in heating the mineral, after being reduced to powder, and before weighing, with the view of expelling any hygrometric moisture, the heat was raised a little too high, by which means, some of the chemically combined water was expelled. The loss in the other analysis, was partly owing to the circumstance that separate portions of the mineral were used in the course of it.