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Stereochemistry.-A graphic method of demonstrating the number of different stereoisomeric forms in which a substance can exist, has been brought forward by Aschan,' as being preferable to the use of models. It is shown in detail that the possibilities of isomerism in ring-systems are more truly seen when the symmetry of the molecule is alone considered; and further, it is demonstrated on these lines that optical activity becomes possible in certain ring-systems in the absence of an asymmetric carbon atom.

If one imagines the plane of a carbon ring of an alicyclic compound as standing vertical to the plane of the paper, it can, provided the ring atoms lie in one plane, be represented by a straight line on the paper. The substituents (omitting hydrogen atoms and unsubstituted methylene groups) are then written, according as to whether they lie on the upper or lower half of the ring, above or below the projected line. Only such forms are identical as can be superimposed either directly or after turning through 180° in the plane of the paper.

The simplest example is afforded by trimethylenedicarboxylic acid,

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A plane of symmetry can be drawn through form 1, which is not possible with 2 and 3, these being mirror images of one another. Aschan defines as optically isomeric only those substances which are mirror images of one another, whilst the term geometrical isomerism applies to all those stereoisomeric forms, active or inactive, which show a dissimilarity in all their physical properties.

On Dihydrobenzenes and on Aromatic Compounds derived from
Hydro-aromatic Substances. By Dr. A. W. CROSSLEY.

Dihydrobenzene.-It has been shown that the dihydrobenzene obtained from dihydroresorcin 2 has the formula.

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that is, the double bonds are in the 1:3 position. Up to the present time it has not been found possible to prepare the hydrocarbon in a pure condition, as it is contaminated with tetrahydrobenzene; but further experiments are being conducted in the hope of obtaining the pure substance by this method.

A second means of producing this same dihydrobenzene seemed to consist in the removal of two molecules of hydrogen bromide from J.C.S., 1903, 83, 494.

1 Ber., 1902, 35, 3389.

dibromotetrahydrobenzene, there being only one possible way in which the hydrogen bromide could be eliminated.

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This reaction has been tried by Baeyer1 and Fortey.2 The latter states that when dibromotetrahydrobenzene is treated with quinoline, dihydrobenzene is formed; but no details of any sort are given. It is therefore to be presumed the author concluded that the dihydrobenzene so formed was the one giving a tetrabromide melting at 184°.

Preliminary experiments have conclusively proved that such is not the case, for the hydrocarbon so obtained gives no trace of the tetrabromide melting at 1840, but only the dibromide melting at 104°5, thus proving it to be A-1:3-dihydrobenzene.

Final experiments, with larger quantities of material are now being carried out.

Aromatic Compounds derived from Hydro-aromatic Substances.— When dichloro-dihydrobenzene 3 (1) and dichloro-dimethyldihydrobenzene 1 (II)

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are treated with excess of phosphorus pentachloride, they are converted respectively into metadichlorobenzene and 8: 5-dichloro-ortho-xylene. Bromine produces the same change with dichlorodihydrobenzene, two atoms of bromine being first added on and then eliminated on distillation as hydrogen bromide.

It was thought that the reaction would be the same with bromine and dichloro-dimethyldihydrobenzene, a supposition which proves to be incorrect; for though the aromatic substances obtained are always substituted ortho-xylenes, they consist for the most part of dichlorobromoxylenes, of which both the possible forms with the chlorine atoms. in the 35 position have been isolated--namely, 3: 5-dichloro-4-bromoortho-xylene and 3: 5-dichloro-6-bromo-ortho-xylene. The work is not in a sufficiently advanced state to warrant the publication of further details.

Edenvale Caves, co. Clare.-Report of the Committee, consisting of Dr. R. F. SCHARFF (Chairman), Mr. R. LLOYD PRAEGER (Secre tary), Mr. G. COFFEY, Professor G. A. J. COLE, Professor D. J. CUNNINGHAM, Mr. G. W. LAMPLUGH, Mr. A. MCHENRY, and Mr. R. J. USSHER, appointed to explore Irish Cuves. (Drawn up by Mr. R. J. USSHER).

IN April 1902 Dr. Scharff and Mr. R. J. Ussher visited some caves in the co. Clare, and decided to explore two at Edenvale, near Ennis, which adjoined each other and proved to be connected.

1 Annalen, 1894, 278.
* J.C.S., 1903, 83, 502.

2 J.C.S., 1898, 73, 948.
J.C.S., 1902, 81, 1536.

5 J.C.S., 1903, 83, 502.

Another system of connected caves was subsequently explored there, and both groups of cavities were found to be prolific in remains of animals now extinct in Ireland, and in human relics of different periods.

Edenvale House stands on a ridge of Carboniferous Limestone, which forms the western side of a deeply cleft anticlinal; in the chasm thus formed lies a lake of relatively great depth, which is surrounded by a steep declivity on all sides but one.

The first two cavities referred to, which have been named the Alice and the Gwendoline caves, open in a low escarpment on the western side of the Edenvale ridge. Their aspect is southerly.

The Alice cave, after running a straight course for 80 feet, was found to terminate in an upward opening that had been filled in with earth and stones, and contained material resembling that found in kitchen middens. At 40 feet from the mouth of this cave a gallery branched off, and connected it with the Gwendoline cave on a lower level.

At 15 feet from the mouth of the Alice cave a projection in the rocky wall was worn smooth, as if by the constant rubbing of creatures which had passed in and out.

In most parts of these caves two strata were distinguishable :—

1st and upper. Brown earth, occasionally containing calcareous tufa. In this stratum was found much charcoal, bones of man and domestic animals in a fragmentary state, and also objects of human art of various descriptions a bone pin or awl, an amber bead, a bracelet of bronze, and another of gold.

2nd. A lower stratum composed of clay, generally of a yellow-ochre tint, but sometimes purplish.

Bones and teeth of reindeer and bear were found chiefly in the latter stratum, and the ursine remains indicated that they belonged to individuals of great size.

Having removed the fossiliferous deposits of the above caves, operations were commenced at the orifice of the second group, opening in the cliff-face under Edenvale House overlooking the lake.

This cave runs 50 feet into the rock, but is traversed by a series of galleries, some of which are wide and confluent. One of these galleries was excavated for a distance of 60 feet, and it was found to be crossed by another cave that led out to the cliff, but whose orifice is blocked.

This system of caves is so extensive and complex that we have named it the Catacombs. It has proved still more fruitful than the former caves in relics of man and of extinct animals. Human bones were frequent, and in one place an assemblage of these included a cranium not far from which there were two stout iron knife-blades. A strap of bronze bearing a buckle was found elsewhere, ornamented with an interlaced pattern in silver plating. In other parts of the Catacombs were chipped flint scrapers, a bone piercer, a tusk of a large boar pierced as if to form an amulet, and a marine shell similarly pierced.

Several marine shells occurred, although the sea is many miles away from the site; also much charcoal and bones of horse, ox, pig, sheep or goat and dog.

Bones and teeth of bear and reindeer were of daily occurrence in excavating the deposits, and in a few cases we obtained pieces of the bones and of the antlers of the great Irish deer (Irish Elk).

The large collections of human and animal remains found in the Eden

vale caves are in course of examination, and the further exploration of the Catacombs is in progress, there being reason to believe that the unexplored portions considerably exceed those that have been examined.

Life-zones in the British Carboniferous Rocks.-Report of the Committee, consisting of Dr. J. E. MARR (Chairman), Dr. WHEELTON HIND (Secretary), Dr. F. A. BATHER, Mr. G. C. CRICK, Dr. A. H. FOORD, Mr. H. Fox, Professor E. J. GARWOOD, Dr. G. J. HINDE, Professor P. F. KENDALL, Mr. R. KIDSTON, Mr. G. W. LAMPLUGH, Professor G. A. LEBOUR, Mr. B. N. PEACH, Mr. A. STRAHAN, and Dr. H. WOODWARD. (Drawn up by the Secretary.) THE Secretary regrets that he has received no reports from members of the Committee, and that the small sum of money voted last year, 57., has not permitted work to be carried on on the usual scale.

In the spring, a chart of the chief fossil shells found at various horizons of the North Staffordshire coalfield was published by the Institute of Mining and Mechanical Engineers.

This chart was drawn up by Mr. J. T. Stobbs, F.G.S., and Dr. W. Hind, F.G.S., and shows a section of the North Staffordshire coalfield, with the marine beds at present known; each bed in the section has opposite to it the shells found in it, or a reference by a number to a shell figured as being found in other beds. This chart is an amplification of a section of North Staffordshire coalfields and on which the horizons at which fossil shells occur, drawn up by Dr. W. Hind and published in his monograph on Carbonicola, Anthracomya, and Naiadites. The authors contend that many of the important seams of the North Staffordshire coalfield can be easily recognised by the mollusca found in connection with them, and that the marine bands form absolutely certain indices of horizons. Collecting has been carried on by Mr. J. T. Stobbs, F.G.S., in Wensleydale and in Teesdale.

The Secretary determined to examine the bed of Limestone mapped in Quarter Sheet 102 S.E., which occurred intercalated in the Millstone Grit beds. Mr. W. Gibson had called attention to this bed, thinking it possible that the Pendleside fauna might be found there, but such is not the case.

The carefully drawn up reports and sections by Mr. Stobbs speak for themselves. The fossils are unfortunately not worth preserving, but the Secretary has been able to identify the great majority, and his identifications are included in the lists in Mr. Stobbs's report.

The district comprising Mickleton and Underthwaite Moors lies between the River Lime and the River Balder (both of which are southern tributaries of the River Tees), and is known as part of the area whence the water-supply of Stockton and Middlesbrough is obtained. At the present time three shafts and a tunnel are in progress of driving, the positions of which are shown in fig. 1. The opportunity was taken of inspecting the débris brought to the surface as a consequence of these works.

The rocks occupying this area belong to the upper portion of the Yoredale series, and consist mainly of finely laminated black shales. The freestones are hard and approximate to the 'gannister' type. The sections afforded by the streams marked (A) were also examined (see fig. 2). The whole series of beds points to a gradual termination of those

recurrences of clear deep-sea conditions during which the Yoredale Limëstones were deposited. In this district the Crystalline Limestones are

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very thin, whilst the thicker ones are shallow-sea deposits, as proved by their detrital character.

No. 2 Shaft (fig. 1) at Bullhill Sike passed through the following

beds :

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From the black shales the following fossils were collected :

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The mouth of the tunnel at No. 3 Shaft is driven in dark shale containing a 1-inch band of Limestone, from which were obtained the following:

Camarophoria crumena.

Orthotetes crenistria.

Productus scabriculus.

Rhynchonella pleurodon.

Spirifera trigonalis?
Phillipsia sp.
Reed-like plant-remains.

In the shale itself Aviculopecten dissimilis was obtained.

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