They fully confirm the opinions expressed above, and from the appearance I should conjecture the brecciation took place when the rock had become a serpentine. In one there is part of a vein (?) containing a pale feebly dichroic variety of hornblende and an associated mineral more like an altered enstatite; probably they are of secondary origin. With the calcite a little dolomite, I believe, is intercrystallized. We have then here a mass of ordinary serpentine which has been crushed into a breccia in situ and consolidated again by infiltration of calcite. Any one who has examined serpentine much in the field will remember that its sharp irregular jointing and brittle nature would cause it to crush more readily perhaps than most other rocks. The whole of the hilly district bordering the Riveria di Levante has been greatly disturbed, and its rocks are often much contorted. During one of these disturbances no doubt the crushing took place. At that time limestones, which still predominate among the sedimentary rocks around this serpentine massif, doubtless extended above it, and the water which percolated downwards from them while they were undergoing denudation deposited the CaCO, with which it was charged in the fissures of the subjacent rock. This has now been exposed to view, all trace of the once overlying rock having disappeared.1 2 Besides the above breccia, I have examined microscopically the two varieties of serpentine, described above, from Levanto. The slide from the more granular rock (with crossing Nicols) is seen to consist chiefly of very characteristic olivine grains, separated by threads (of variable thickness) of serpentine, about equal quantities of the two minerals being present. There are the usual clots of opacite. In short, the appearance of the ground-mass of the slide is so similar to what I have already described in a Cornish serpentine, that repetition is needless. Enstatite and augite are both present, as I have proved by optical tests, etc., and perhaps also a little diallage. I think the first mineral rather predominates, but there are difficulties in determining the crystalline system of some of the grains. Endomorphs of opacite are rather commoner than is usual in the enstatite. There is a little picotite. The other and compact variety exhibits a more complete conversion into serpentine. No olivine remains to show chromatic polarization, though here and there a grain is still doubly refracting. In this also there is (as might be expected) more opacite. It often forms continuous strings, is more or less present in the grains (formerly olivine), being either disseminated throughout them, or in bands towards the exterior. Diallage and enstatite are both present, the latter being surrounded by a border of a serpentinous mineral, into which the planes of principal cleavage are continued, and are often picked out by thin lines of opacite. The cleavages 1 I should perhaps state that there is nothing to favour the idea of this crushing having been sudden, or associated with any exceptional amount of heat. It may have been the result of long-continued pressure and yielding now here now therepossibly, indeed, the process of crushing and cementation may have been repeated more than once. 2 Quart. Journ. Geol. Soc. vol. x. sec. xxxiii. p. 916. parallel to ∞ P are indicated by thin lines of serpentine. The same change is common in other serpentine rocks which I have examined. This second mineral can be seen with a hand-lens, forming a talclike border to the unaltered crystal; probably it is nearly allied to that mineral. One small grain of picotite is present, and some of the most minute opacite is dichroic, and is probably manganese. Through the kindness of Prof. Liveing a specimen of this second rock has been examined for me at the Cambridge University Laboratory by Mr. C. T. Heycock, of King's College, to whom I return my best thanks. Together with his analysis I reprint for comparison those of serpentines very similar in appearance from Ayrshire and Cornwall. All dried at 100° Cent. In the Levanto specimen there was the slightest trace of CO. Hydrochloric acid dissolved 95.54 per cent. of the mass, leaving 4:46 residue as a slightly green amorphous powder. The per-centage of alumina here, as in the Ayrshire specimen, is larger than I should have anticipated, as I cannot see a trace of felspar. Part of it, however, may be due to the pyroxenic constituents, and the rest to picotite. The constant presence of nickel is interesting. My next visit was to the quarries from which is obtained the celebrated Verdi di Prato, for centuries one of the most important decorative stones in the valley of the Lower Arno. These are at Figline, a little village between two and three miles from Prato, a town between Florence and Pistoia. Here also the serpentine, as may be seen from the railway, occupies a considerable tract of hilly country, and rises from beneath the calcareous strata which are so common in this part of the Apennines. Figline lies on the last slopes of the hills, and on approaching it from Prato the serpentine (which has the usual dusty purplish-brown or greenish-brown colour and characteristic weathering) is seen forming the right bank of the valley; while on the left bank is exposed an indurated argillaceous rock, disturbed and sharply jointed, its aspect suggesting, as does the contour of the serpentine mass itself, that the latter rock is intrusive. The quarries, which are rather numerous, are situated on the hill-side behind Figline. Almost directly on quitting the village at the lower end, we come upon coarse gabbro, of the usual character, but very rotten, and after ascending perhaps a hundred. 1 Quart. Journ. Geol. Soc. vol. xxxiv. p. 771. 2 Quart. Journ. Geol. Soc. vol. xxxiii. p. 925. feet, reach quarries in this rock, some of considerable size. The gabbro is coarsely crystalline, consisting of plagioclase felspar (resembling labradorite), partly of a dull bluish colour, partly changed into white "saussurite" and greenish diallage, with a rather silvery lustre, the crystals commonly varying from" to " diameter, and some dull green spots possibly denoting altered olivine. The slide, however, which I have had prepared, does not show any of the last, but consists of plagioclase felspar more or less altered, diallage, ordinary augite, and a little secondary hornblende.' The rock is locally known as pietra di macchina, and is quarried for mill-stones. It varies a little in the relative amount of diallage and felspar and evenness of crystallization, but is, on the whole, very uniform in character. I had not time to trace out its limits, but the size of the mass must be considerable. Bearing away to the right and slightly ascending, we approached the serpentine, which forms hereabouts the upper part of the hill. The actual junction of the two rocks is obscured by vegetation, soil, and detritus, but in a water-course I obtained a fair section, which satisfied me that the gabbro was intrusive in the serpentine. Quarries in the latter rock are still more numerous than in the former, so that, though all the natural surfaces are much decomposed, there is no difficulty in obtaining a good supply of specimens. The general character of the serpentine appeared to be very uniform-a ground-mass of a dull purple with a tinge of green irregularly mottled by the latter colour; in this are scattered rather small crystals of a greenish mineral resembling enstatite. Thin veins of green steatite are not unfrequent. After long exposure the rock becomes of a pale grey green. It is sharply but irregularly jointed, the joints often coated with a film of white steatite, and sometimes becoming brown by exposure. In general character the rock is identical with those already described and with that of the Lizard, so that, from examination in the field alone, one might fairly claim for them a similar origin. A microscopic slide shows no unchanged olivine, but in parts, as in the last described, a structure is visible indicating that this serpentine also is an altered olivine rock. I do not find any unaltered enstatite or augite, but several grains resembling the talcose mineral described above. In another slide, cut some years since from a specimen purchased in Florence, the enstatite still shows faint tints and a little of the serpentine in the strings' exhibits slight chromatic polarization. On returning from the quarries I descended into the glen above Figline, and a short distance from the latter found stratified rock by the road-side. This at first was an argillaceous rock, with concretions, looking as if it had been much crushed. A little nearer occurs a harder, bedded rock, bands of which have a flinty texture and fracture of a dull reddish colour. The peculiar sharp jointing, baked 1 An analysis of the diallage is given by D'Achiardi, vol. ii. p. 84, and of the felspar (labradorite), id. p. 104. The rock is commonly called ". granitone" by Italian geologists. 2 I believe this is the "gabbro rosso" of some authors. aspect, and wavy outline of the surface of the strata, which dip at some 15° away from the serpentine, are almost enough to prove the latter intrusive. But by ascending the bed of a streamlet, and climbing up a little to the right, more conclusive evidence may be obtained. Here we have the section roughly sketched in the annexed diagram. A talus, D, it is true, masks the actual junction of the serpentine and the stratified rock; but the state of the rock in the little cliff is almost enough to prove intrusion. However, on looking carefully about, I found a complete proof. At A, about four yards from B, the last exposure of the serpentine, and six yards from the base of the cliff (measured on the slope), and on a lower level by a few feet, was a small slab of the stratified rock yet adhering to the serpentine. This collocation places the intrusive character of the latter beyond all doubt. RELATIONS OF SERPENTINE AND SEDIMENTARY ROCKS, NEAR FIGLINE. B Serpentine,ALIFORNIA, D Talus Microscopic examination of a specimen from the upper part of D has produced interesting results. It consists of a very fine muddy or silty ground-mass, in most parts stained of a deep red, crowded with minute organisms, some resembling Sponge spicules, often triradiate; others resembling Polycystinæ or Foraminifera, such as Orbulina or Lagena. They appear to be siliceous, and the internal parts exhibit the black cross of aggregate polarization. Two or three are pretty certainly minute Gasteropods. To determine the position of the rest is not easy. One eminent student of Microzoa, to whom I submitted the slide, claims the majority for Polyzoa, another for Polycystine and Sponge spicules. If I may presume, without having made such organisms a special study, to express an opinion, it would be that while some certainly much resemble Polyzoa, others are singularly like Polycystinæ. That all appear to be siliceous is not conclusive, because under the circumstances replacement may have taken place. Thus we are unable from these remains to fix the precise geologic age of the rock, but still may fairly class it with the strata of the immediate vicinity, which are, I believe, Upper Cretaceous. DECADE II.-VOL. VI.-NO. VIII. 24 In the Mineralogical Museum at Florence, Professor Grattarolo (to whom I am much indebted for information on localities, etc.), showed me a collection of serpentine and gabbro from Impruneta, a few miles from the city. These had the same general character as the above; but both rocks were much decomposed, so that, on hearing there were no excavations, I did not think it worth while visiting the locality, as I probably should not have been able to learn more than I could from the specimens. These serpentines, then, and no doubt several other isolated patches in the Ligurian Apennines, which I had not the opportunity of visiting, must be added to the rapidly increasing group of altered olivine rocks, primarily of igneous origin. To these also belong, as I have already pointed out, the serpentines of Elba, and in our own country those of the Lizard, Ayrshire, Portsoy, with other parts of Scotland; and as I shall show on a future occasion-of North Wales. To these also must be added some of the Alpine serpentines. Here, however, careful discrimination will be needed, for though no doubt true serpentine is present in the Alps, some of the rocks commonly mapped under that name have received it improperly, being only serpentinous, i.e. rocks into whose composition other minerals enter very largely, and in many cases simply serpentinous schists. Further, it is impossible to avoid being struck with the frequent association of serpentine and gabbro; at these four localities in Italy, the two extremes being a good hundred and twenty miles apart (and I believe in several others), at the Lizard in Cornwall, and on the coast of Ayrshire-to speak only of those which I have myself visited, we have gabbro intrusive in serpentine. This can hardly be a mere coincidence. These gabbros also are remarkably like one another in aspect. Some observers, indeed, have asserted that the serpentine is the result of transmutation of a gabbro. Now that the microscope is used in petrology, I do not think we shall hear much more of that statement, which in many cases was founded only on very hasty examination in the field, and has seldom a better base than the fact that serpentine is one of those minerals which, like some people, can make a great show with but little means. It is often instructive to see how "serpentinous" a rock will appear to the eye, which, on careful examination, proves to be mainly composed of other minerals. Reflection, too, should have suggested to petrologists that felspar is not an easy mineral to remove from a rock. The case of greissen, tourmaline-rock, etc., may, I am aware, be quoted; but these are always comparatively local, while in the case of serpentine we should have to pseudomorphose masses of gabbro containing billions and billions of cubic yards so perfectly that no trace of the felspar remained, and by so strange an agent that its action is found to have stopped abruptly. The representatives, then, of altered olivine-gabbros, will be found in the troktolite group; and where gabbro and pure serpentine (i.e. a rock the ground-mass of which consists almost entirely of hydrous silicate of magnesia with some oxides of iron) are associated, the two rocks are of independent origin. It will be well for travellers to observe carefully |