June 14, 1883] 



NA TURE 



167 



some little-know n fossil-, has a closed ring of basals ; and even 

 in Atekcrinus they are quite small and insignificant. 



(2.) In all recent Comatula, in the Ptntacrinidit , and in 

 Bathyerinus, the oral plates of the larva become resorbed as 

 maturity is approached. In Thaumatocrinus, however, they are 

 retained, as in Hyocrimis, Rhiaocrinus, and Iloiopus, repre- 

 sentatives of three different families of Neocrinoids. 



(3. ) There is no Neocrinoid, either stalked or free, in which 

 the primary radials remain permanently separated as they are in 

 Thaumatocrinus, and for a short time after their first appear- 

 ance in the larva of ordinary Crinoids. The only Pakeocrinoids 

 presenting this feature are certain of the Rhodocrinidcv, e.g. 

 Riteocrintis, Rhodocrimu, Thylacocrinus, &c. In the two latter 

 and in the other genera which have been grouped together with 

 them into the section Rhodocrimtts there is a single interradial 

 intervening between every two radials, an I resting on a basal 

 just as in Thaumatocrinus. But in the Lower SilurHi Rcteo- 

 crinus the interradial areas contain a large number of minute 

 pieces of irregular form and arrangement. 



(4.) It is only, however, in Reteocrinus and in the allied genus 

 Xenocrinus, Miller, which is also of Lower Silurian age, that 

 an anal appendage similar to that of Thaumatocrinus is to be 

 met with. 



Of the four distinguishing characters of Thaumatocrinus, 

 therefore, one appears in one or perhaps in two genera of Coma- 

 tirfu : another is not to be met with in any Comatula, 

 occurring in certain stalked Crinoids ; while the two remaining 

 characters are limited to one family of the PaUeocrinoids, one of 

 them being peculiar to one or at most two genera which are 

 confined to the Lower Silurian rock-. 



Their reappearance in such a specialised type as a recent 

 Comatula is therefore all the more striking. 



Geological Society, May 23. — J. W. Hulke, F.R.S., pre- 

 sident, in the chair. — Ernest Le Neve Foster and Richard 

 JLiullen Newton were elected Fellows of the Society. — The 

 following communications were read: — On the basalt glass 

 (tachyly te) of the Western Isles of Scotland, by Prof. J. W. Judd, 

 F.R.S., Sec.G.S., and G. A. J. Cole, F.G.S. Basalt glass or 

 tachylyte is a rare rock, although very widely distributed. In 

 the Western Isles of Scotland it has, by the authors of the paper, 

 been detected in five localities only, namely, Lamlash (Holy 

 Isle) near Arran, the Beal near Portree in Skye, Gribun and 

 Some in Mull, and Screpidale in Kaasay. Basalt glass is always 

 found in the Hebrides as a selvage to dykes, though elsewhere 

 it has been described a- occurring under other conditions where 

 rapid cooling of basaltic lava has taken place. Some of the 

 varieties of basalt glass in the Hebrides differ from any hitherto 

 described by their high specific gravity (2'8 to 2'a) and by their 

 low percentage of silica (45 to 50). This basalt glass is fre- 

 quently traversed by numerous joints ; it is occasionally finely 

 columnar, and sometimes peilitic in structure. From the acid 

 glasses (obsidian) it is distinguished by its density, its opacity, 

 its magnetic properties, and especially by its easy fusibility, from 

 which the name of tachylyte is derived. By its greater hardness 

 it is readily distinguished from its hydrated forms (palagonite, 

 &c). In its microscopic characters basalt glass is found to 

 resemble other vitreous rocks ; thus it exhibits the porphyritic, 

 the banded and fluidal. the spherulitic, and the perlitic struc- 

 tures. In the gradual transition of this rock into basalt, all the 

 stages of devitrification can be well studied. The difference 

 between these locally developed basalt glasses and the similar 

 materials forming whole lava-streams in the Sandwich Islands 

 was pointed out in the paper, and the causes of this difference 

 were discussed. It was argued that the distinction between 

 tachylyte and hyalomelane, founded on their respective behaviour 

 when treated with acids, must be abandoned, and that these 

 substances must be classed as rocks and not as mineral species ; 

 the name basalt glass was adopted as best expressing their rela- 

 tions to ordinary basalt, the term tachylyte being apptied to all 

 glasses of basic composition and being used in contradistinction 

 to obsidian. — On a section recently exposed in Baron Hill Park, 

 near Beaumaris, by Prof. T. G. Bjuney, F.R.S., Sec.G.S. 

 The author, about three years since, observed some imperfect 

 exposures of a felsitic grit in the immediate vicinity of the normal 

 schists of the district in a road which leads from Beaumaris 

 cemetery to Llandegfan ; but last summer had the opportunity, 

 through the courtesy of Sir R. B. Williams, of examining the 

 cuttings made in constructing a new drive, which runs through 

 Baron Hill Park, very near the above outcrops. After tracing 



the normal schists along the steep scarp of the hill, he came, 

 after an interval of about 60 yards, covered by soil and 

 vegetation, to a massive gray grit consisting of quartz, felsoar, 

 and minute fragments of compact felsi'e, which now and 

 then attain a larger size, being an inch or so across. These 

 grits, which 1 ass occasionally into hard compact mudstones 

 (probably more or less of volcanic origin), can be traced for some 

 350 yards to the neighbourhood of the above-mentioned road, 

 which is crossed by a bridge ; and a short distance on the other 

 side of this is a considerable outcrop of the grit, which in places 

 becomes coarsely conglomeratic, containing large fragments of 

 the reddish quartz-felsite so common on the other side of the 

 straits, in the beds at or below the base of the Cambrian series. 

 The schi-ts appear to dip about 20° E.S.E., the grits about 25° 

 E. The author, after describing the mi lie structure of 



the various rocks noticed, pointed out that this section, though 

 the junction of the two rocks is probably a faulted one. has an 

 important bearing on the question of the age of the Anglesey 

 schisis, micaceous and chloritic. The Survey regards them as 

 altered Cambrian ; it has even been suggested that they may be 

 ol Bala age; others have regarded 'hem as Pebidian. Now- the 

 felsitic grits and conglomerates cannot be newer than the Cam- 

 brian conglomerate of the mainland, regarded by Prof. Hughes 

 as the base of the true Cambrian, and are probably older, cor- 

 responding with some part of the series between it and the great 

 masses of quartz-felsite which are developed near Llyn Padarn 

 and Porl Dinorwig, which serie lithol gically and stratigraphi- 

 cally corresponds with the typical Pebidian of Pembrokeshire. 

 Hence, as the Angle-ey schi-ts are in the full sense of the term 

 metamorphic rocks, and the "Pebidian" but slightly altered, 

 show s that the former must be much older than the 

 latter, and so be distinctly Arcluvan. — On the roc's between the 

 quartz-felsite and the Cambrian stries in the neighbourhood of 

 Bangor, by Prof. T. G. Bonney, F.R.S., Sec.G.S, This 

 district has already been the subject of papers by the author 

 (Quart. Jburn. dog. Soc, vol. xxxiv. p. 137), and by Prof. 

 Hughes (vol. xxxv. p. 682), who differs from him in restricting 

 the series between the quartz-felsite and Cambrian conglomerate 

 to little more than the bastard slates and green breccias of 

 Bangor mountain. The author has traced on the south-east 

 side of the Bangor-Caernarvoii road a well-marked breccia 

 containing fragments of purple slate mixed with volcanic 

 materials, below the absve-named Bangor series, for more 

 than a mile. At a lower level he has traced another well- 

 marked breccia, chiefly of volcanic materials, for half a 

 mile ; and, lastly, a grit and conglomerate, apparently resting 

 on the quartz-felsite named above, com posed of materials derived 

 from it. This has been traced on both sides of the road men- 

 tioned above for nearly two miles. For these and for other 

 reasons given in the paper, the author is of opinion that, as he 

 formerly maintained, there is a continuius upward succession on 

 the south-east side of the road, from the quartz-felsite at Brithdir 

 to the Cambrian conglomerate on Bangor mountain. The 

 district on the north-west side of the road is so faulted that he 

 can come to no satisfactory conclusions. The author ii in 

 favour of incorporating the ab ive-named quartz-felsites with the 

 overlying beds as one series, corresponding generally with the 

 Pebidian of South Wales ; older than the Cambrian, though 

 probably not separated from it by an immense interval of tune. 

 An analysis of the Brithdir quartz-felsite by Mr. J. S. Teall, 

 was given, from which it appeared that the rock corresponds 

 very closely with the " devitrified pitchstone " of Lea rock in 

 the Wrekin district, described by Mr. Allport, but differs con- 

 siderably in composition from those in the Ordovician rocks of 

 North Wales. 



Edinburgh 



Royal Society, May 21. — Mr. Robert Gray, vice-president, 

 in the chair. — Obituary notices were read of Sheriff Hallard, 

 Dr. John Muir, Friedrich Wohler, Sir J. Rose Cormack, M. P., and 

 Dr. Morehead. Mr. John Aitken, in a note on the moon and the 

 weather, observed that the phenomenon of the old moon in the 

 new moon's arms was not always visible in a very clear atmo- 

 sphere, but that other meteorological conditions seem to be 

 requisite. He suggested that the earthshine might be greatly 

 intensified by a cloud laden atmosphere to the west of the 

 observer. — Mr. D. B. Dottread a piper on the acids of opium, 

 in which he stated that, contrary to the general opinion, the 

 principal acid in opium, judged by its acidifying powers, is 

 sulphuric and not meconic acid, a considerable portion of the 



