the per-centage required by any mineral which can stand intermediate between natrolite and scolezite (galactite, therefore, is to be referred to one or other of these species; and as the soda greatly preponderates, it is to be considered as merely a variety of natrolite, the soda mineral); but, should we find that any or all of the substances at present under consideration do so agree, then we are entitled to consider them distinct species. Though the minerals mesolite and mesole are well known by name, I believe there is considerable difference of opinion as to whether both or either are distinct species. This may result perhaps from a paucity of analyses, perhaps from the published analyses having been performed on impure or even mixed specimens; for I am afraid, that, even after years of teaching, the eye cannot discriminate some of the radiated zeolites; it rarely is here assisted by form; colour, hardness, and specific gravity do not afford much aid; from analysis alone do we obtain decisive information. I very decidedly consider mesolite and Faröelite (mesole) to be thoroughly good species, and quite distinct from each other; and hope the following analyses, taken in conjunction with those already published, will make this evident. Mesolite.-1. From Talisker in Skye, there called cottonstone; colour white, in delicate interlacing crystals, which, when crushed, become the "mealy zeolite" of some authors. or 12.831 = 11401 = 8·267 = 8 100.629 (NaO, 2CaO) 3SiO3 +3(Al2 03, SiO3) +8HO, 2(CaO, SiO8+A12 O, SiO3+3HO) + (NaO, SiO3 + A12 03, SiO3 2 atoms of scolezite + 1 atom of natrolite +2HO), the per-centages of which are, The analyses by Berzelius, V. Fuchs, and Gehlen, agree admirably with this formula. (CaO, NaO) SiO3 +Al203, SiO3 +3HO has been given the per-centages of this are, The only analysis which comes near this is that by Friesmuth from Hauenstein. Rose (in his Krystallo-chemische Mineralsystem, p. 39) gives the mineral from that locality this formula, and calls it mesolite. Dana, again, makes it mesole, with an equibasic formula, with which it seems indeed best to agree (see note to Faröelite). Hausmann, however (Handbuch, p. 801), remarks, "der sogenannte Mesolith von Hauenstein ist nach Haidinger mit Comptonit uberzogener Zeolith." And this opinion, grounded probably on inspection, would seem to be confirmed by a chemical consideration of the subject, as an admixture of Comptonite with natrolite would result in some such compound; the former furnishing the lime, diminishing the quantity of silica and soda, and slightly increasing that of the alumina and water of the last-mentioned mineral. 2. From Storr in Skye; colour white, in delicate feathery tufts (powdered mineral absorbs 574 per cent. of moisture). 3. At Kilmore in Skye, mesolite occurs in yellowish-white radiated crystals, forming solid masses, very different in appearance from the specimens at the above localities, and having much resemblance to natrolite. This being the only mesolite I have seen the crystals of which are large enough for measurement, I forwarded some chips to Mr. Greg: he finds MM'=89°. 4. From the cave in Naalsöe, Faröe; in downy tufts. Faröelite (Mesole).-1. From Storr in Skye; bluish-white (NaO, 2CaO) 2SiO3 +3(Al203, SiO3)+8HO, the per-centages of which are,— 2. From near Portree in Skye; in confused white nodules. 3. From Uig in Skye; associated with a (?) new mineral and analcime. The specimens at this locality are white radiated nodules, filling the whole cavity. Two analyses of different specimens were made. * Compare analyses of Berzelius and Thomson. The sole chemical difference, therefore, between mesolite and faröelite is one equivalent of silica*; but the mineralogical distinctions, between typical specimens, at least, are numerous and well marked. Faröelite invariably occurs either in implanted and isolated globules (I observed a single instance in the island of Naalsöe, where these globules were prolonged into stalactites of about 3 inches in length), or as a mammillated coating of the rock. These spheres, generally of a bluish colour, are, though radiated in their structure, solid at the circumference as at the centre, and have a decided pearly lustre on one, apparently a cleavage face. Mesolite, again, is generally seen in delicate, free, dead white fibres, which have no pearly lustre: in the finelycrystallized Iceland specimens, as also in those from Uig, the lustre is vitreous. One cavity in the rock will contain mesolite; another close by, Faröelite: when both occur in the same cavity, the latter is invariably nearest the rock. At Storr, as also all over Faröe, Faröelite occurs in solid spheres of a blue tint, with free plumes of dead white mesolite implanted on them, perfectly distinct in structure and appearance; in fact, out of twelve zeolites which may be found at the Storr, Faröelite is, with the exception of chabasie, the first which has been deposited in the cavities of the rock, mesolite the last, or one of the last. Again, the one mineral is of common occurrence at a locality where the other is rare, or altogether absent; at the next locality the reverse may hold good; and so also it is in Faröe. The nomenclature of these zeolites seems to me to be in a sad state of confusion :-we have mesotype, mesolite, mesole (also * From the analyses of Hisinger and Thomson, Faröelite seems to occur at Annaklef and Bombay with the formula 3(NaO, CaO) 2SiO3+3(Al3 O3, SiO3)+8HO, the per-centages of which are the mesolin of Berzelius, but that is Levyne). I would propose that the unmeaning mesotype be exchanged for the expressive natrolite; that mesolite, as being in reality the intermediate mineral, be retained; and that mesole give place to Faröelite, after the locality whence we obtain the choicest specimens of the mineral. From their composition they will rank as follows: Faröelite Natrolite . SINCE . VII. On an Improved Induction Apparatus. INCE attempts have been made to construct induction apparatus of larger dimensions in order to obtain electric currents which should, as it were, stand midway between those obtained from the electric machine and those obtained from the voltaic battery, several physicists and artists have been occupied with the study of the phænomena connected with the subject. Probably what has already been accomplished is far from the perfection which it is possible to confer upon these instruments; and there is no strong reason against the supposition, that, with comparatively small means, sparks several inches in length may be obtained at the extremities of the wire of the induction coil, if the necessary insulation can be effected without removing the wire too far from the central core. The surrounding layer must be completely impenetrable to sparks which might spring from one series of coils to another. In the year 1854 I constructed an induction apparatus in which I endeavoured, as M. Sinsteden has done, to turn to account the advantage possessed by magnets of the horseshoe form over bar magnets. The result was not that which I hoped for; for after the removal of the iron crosspiece which united both limbs of the magnet, each bar singly showed a strong induction current. It may be that the magnetic inertia of the massive piece of iron is the cause of this, although subsequent experiments on the advantages of bundles of iron wire over the massive iron core showed that too much weight must not be attached to the action of the iron by its temporary magnetism. The same was observed by Prof. Poggendorff. According to him, * From Poggendorff's Annalen, May 1856. |