We are happy to receive constructive comments of our paper by Moczydlowska and thank her for adding new relevant data. We will attempt to reply to each of her points.

In a recent paper Johnston et al. (1994) have provided an innovative interpretation of the tectonostratigraphic relationships between distinct terranes juxtaposed along the Intra–Sudetic Fault in the Sudetes Mountainsof the Polish Variscides. They identified this fault as a major crustal fracture between Gondwana and Baltica, rramed the Tornquist Suture, resulting from the closure of the Tornquist Sea during the Caledonian orogeny. This interpretation is based on new U/Pb ages on zircon and titanite from igneous and metamorphic rocks (Oliver et al. 1993), field observations and reassessment of pre–existing data. Previously, the Sudetes were generally thought to haveformed during the Hercynian orogeny, although Caledonian age deformation was also inferred (Oberc 1977, 1986; Don 1984, 1986, 1990).

In Part I of a Memoir “On the Craniology of the People of Scotland,” published in the Transactions of the Society twelve years ago (vol. xl), I described the anatomical characters of 176 skulls, the majority of which had been obtained in the counties south of the Clyde and the Tay. The dimensions, form and proportions of the cranial box and of the face were examined, the cranial and facial indices were computed, several of the skulls were figured from the vertex, lateral aspect and face, and mesial sagittal sections of the skulls with radial and other measurements were reproduced. The Memoir gave the fullest account of the characters of the skulls of the modern Scottish people which had been produced up to that time. In the concluding paragraph I stated that I had formed a collection of skulls of the prehistoric in-habitants of Scotland, which I proposed to describe to the Society in Part II of the Memoir, and to discuss the general ethnographical relations of the Scottish people. From various causes the presentation to the Society of this Part has been too long delayed.

On the 3d of November last, Sir James Hall and Dr Rutherford asked me to repeat with them some experiments on what has been called Animal Electricity, which were first performed by Dr Galvani, Professor of Anatomy at Bologna, and of which an account had been communicated by Mr Seguin of Paris to Dr Black, in a letter dated Paris, 3d August.

The quality and richness of Perthshire's natural environment were formative influences on a young James Croll (1821–1890), which left him with a life-long appreciation of nature, landscape and natural meditation. Although Croll himself declares to have had little interest in geology in his earlier years, it became a central theme of his scientific understanding, which implies the clear influence of both his local environment and of his father David, a stonemason. His family and friends also shaped him in other ways, not least his love of reading, his unconstrained thinking and intellectual acuity. He inherited his father's moral character, amiability and an excitement about intellectual inquiry, which drew friends to him who made great efforts to assist him in his work, both personally and professionally, and played a role in his being offered a position by James Geikie with the Geological Survey of Scotland. Croll's financial position was often precarious; he spent a good deal of his life in relative poverty. Whilst this affected his opportunities for formal learning, it may well have led to his ability to think creatively and to seek answers more broadly than he might have if he had been able to engage in a more formal education. Ill health, which affected him throughout his life, could be seen to both hamper his work – but also through circumstance lead him to pursue a more academic path, as other routes of work were shut off to him. Ultimately Whitefield, Wolfhill and the wider Perthshire countryside in which he grew up can clearly be seen to have influenced his life in many ways, even, perhaps, to the extent of his chosen surname.

Dinosaur body fossil material is rare in Scotland, previously known almost exclusively from the Great Estuarine Group on the Isle of Skye. We report the first unequivocal dinosaur fossil from the Isle of Eigg, belonging to a Bathonian (Middle Jurassic) taxon of uncertain affinity. The limb bone NMS G.2020.10.1 is incomplete, but through a combination of anatomical comparison and osteohistology, we determine it most likely represents a stegosaur fibula. The overall proportions and cross-sectional geometry are similar to the fibulae of thyreophorans. Examination of the bone microstructure reveals a high degree of remodelling and randomly distributed longitudinal canals in the remaining primary cortical bone. This contrasts with the histological signal expected of theropod or sauropod limb bones, but is consistent with previous studies of thyreophorans, specifically stegosaurs. Previous dinosaur material from Skye and broadly contemporaneous sites in England belongs to this group, including Loricatosaurus and Sarcolestes and a number of indeterminate stegosaur specimens. Theropods such as Megalosaurus and sauropods such as Cetiosaurus are also known from these localities. Although we find strong evidence for a stegosaur affinity, diagnostic features are not observed on NMS G.2020.10.1, preventing us from referring it to any known genera. The presence of this large-bodied stegosaur on Eigg adds a significant new datapoint for dinosaur distribution in the Middle Jurassic of Scotland.

The development of non-toxic and inexpensive materials for arsenic removal is required due to water sources being polluted by arsenic in many countries around the world. The main aim of this study was to characterise the capacity and behaviour of Mg/Fe layered double hydroxides/biochar [Magnesium/Iron-Layered Double Hydroxide (Mg/Fe-LDH)] composite for arsenate adsorption from solution. Apple tree pruning residues were used to produce biochar at 500 °C under oxygen-limited atmosphere. Mg/Fe-LDH-biochar was synthesised using a spontaneous in situ co-precipitation method. Batch experiments were used for the assessment of the kinetics, isotherms, and the effects of initial solution pH (4, 6, 8, and 10), ionic strength (0.01, 0.1, and 0.2 mol L−1), and co-occurring anions (carbonate and phosphate) on the arsenate removal. Scanning electron microscope images showed Mg/Fe-LDH were loaded on the biochar porous structure, and X-ray diffraction analysis affirmed the presence of crystalline LDH minerals in Mg/Fe-LDH-biochar. Surface modification of biochar by Mg/Fe-LDH increased the maximum arsenate adsorption capacity (3.6 mg g−1) ten times compared to unmodified biochar (0.35 mg g−1). Arsenate removal capacity increased from 4.2 % to 54.2 % with modification of biochar by Mg/Fe-based LDH. Kinetic studies indicated that >90 % of Mg/Fe-LDH-biochar arsenate adsorption from a starting concentration of 10 mg L−1 occurred in the first 120 min. Pseudo-second order and Langmuir models described well the kinetics and isotherm of arsenate adsorption by biochar and Mg/Fe-LDH-biochar. Mg/Fe-LDH-biochar showed maximum arsenate removal capacity at pH 6. Increasing solution ionic strength and the presence of phosphate and carbonate anions suppressed arsenate removal by Mg/Fe-LDH-biochar. In summary, surface modification of biochar using Mg/Fe-LDH produced a potentially more cost-effective, locally available, reusable, and non-toxic arsenic adsorbent for decontamination of surface- and groundwater.

On the Fossil Plants collected during the Sinking of the Shaft of the Hamstead Colliery, Great Barr, near Birmingham.

The area comprised in the county of Stafford embraces five coal fields—

I. The Goldsitch Moss Coal Field, in the extreme north-east of the county.

II. The Cheadle and Churnet Valley Coal Field.

III. The Wetley and Shafferlong Coal Field.

IV. The Coal Field of the Potteries.

V. The South Staffordshire Coal Field.

The three first mentioned are of small extent, and as I know little of their fossil flora they are omitted from this series of papers on the Carboniferous Flora of the Staffordshire Coal Fields.

I, however, devote a separate communication to the fossil plants met with while sinking the shaft of the Hamstead Colliery, Great Barr, as a considerable part of the rocks passed through during this operation is clearly Upper Coal Measures, not Permian, as has been generally stated. The palæontological evidence, therefore, becomes of special importance in determining the age of the red shales occurring in the upper part of this sinking, which have been usually mapped as Permian.

It is now many years since Dr Whewell drew the attention of the Cambridge Philosophical Society to the courageous, if somewhat Quixotic, attempts of Hegel to cast discredit on Newton's law of gravitation, and on the mathematical demonstrations of Kepler's laws given in the “Principia.” At the time when Whewell wrote, it would probably have been difficult to find in Britain any one ready to maintain the cause of Hegel in this matter, or even to hint that the astounding arguments of the Naturphilosophie flowed from any deeper source than self-complacent ignorance.

The present state of matters is different. The philosophy of Hegel is now for the first time beginning to have a direct and powerful influence on British speculation. Men are beginning to study Hegel; and an author whose works confessedly demand the labour of years, if they are to be fully understood, can hardly be studied at all except by devoted disciples. A man whose determination to master Hegel's philosophy survives the repelling impression which the obscurity and arrogance of the philosopher are sure to produce at first, is very likely to be carried away by the calm assumption of omniscience which runs through Hegel's writings. It is not, therefore, surprising that Dr Stirling extends his admiration to Hegel's physical positions; and if he does not venture to say that Hegel's proof of Kepler's laws is right, at least feels sure that it would repay the attention of mathematicians.

[Since this second instalment of my paper was read to the Society my attention has been called to a remarkable investigation by Hertz; in which the circumstances of collision of two elastic spheres are fully worked out, under the special limitations that both are smooth, and that their deformations are exceedingly small. This forms a mere episode in the paper, which is devoted mainly to the statical form of the problem of deformation; as, for instance, the case of the ordinary apparatus for the production of Newton's rings. But it contains a definite numerical result; giving for the duration of impact between two iron spheres of 50mm diameter, which encounter one another directly with a relative speed of 10mm per second, the value 0s·00038. This seems to be the earliest reckoning of the time of collision. The experimental verification of Hertz' formulæ was undertaken with success by Schneebeli, who obtained results in close accordance with them. His mode of measuring the duration of impact was defective, though ingenious.

When any one of the following tables has been given in the past to an extent useful at the present time, it will be found by the computer that the necessary volume is only with difficulty accessible and hardly ever to be purchased. That these tables are obviously useful is perhaps all that need be said in justification of their more extended computation.

The celebrated Bouguer was the first who discovered the important fact, that the eye can detect a very small difference between two similar illuminated surfaces, when viewed at the same moment,—the only principle which has yet been applied with any degree of success, in determining the relative illuminating powers of artificial flames. The following is perhaps the most commodious application of this principle, to determine the relative illuminating powers of different artificial lights, particularly of coal and oil gas. The instrument, or photometer, which I employ for this purpose, is extremely simple. It consists of a rectangular box, about an inch and a half, or two inches square, open at both ends, and blackened within for the purpose of absorbing the stray-light.

While the external infiltration of water has been identified from modern geothermal and/or fossil hydrothermal systems through stable isotopes, the physicochemical boundary conditions like the initial oxygen isotopes of water $( {{\rm \delta }^{ 18}{\rm O}_{\rm W}^{\rm i} } ) $ and rock as well as alteration temperature were implicitly presumed or empirically estimated by the conventional forward modelling. In terms of a novel procedure proposed to deal with partial re-equilibration of oxygen isotopes between constituent minerals and water, the externally infiltrated meteoric and magmatic water are theoretically inverted from the early Cretaceous post-collisional granitoid and intruded Triassic gneissic country rock across the Dabie orogen in central-eastern China. The meteoric water with a $ {{\rm \delta }^{ 18}{\rm O}_{\rm W}^{\rm i} } $ value of −11.01 ‰ was externally infiltrated with a granitoid and thermodynamically re-equilibrated with rock-forming minerals at 140°C with a minimum water/rock (W/R)o ratio around 1.10 for an open system. The lifetime of this meteoric hydrothermal system is kinetically constrained less than 0.7 million years (Myr) via modelling of surface reaction oxygen exchange. A gneissic country rock, however, was externally infiltrated by a magmatic water with $ {{\rm \delta }^{ 18}{\rm O}_{\rm W}^{\rm i} } $ value of 4.21 ‰ at 340°C with a (W/R)o ratio of 1.23, and this magmatic hydrothermal system could last no more than 12 thousand years (Kyr) to rapidly re-equilibrate with rock-forming minerals. Nevertheless, the external infiltration of water can be theoretically inverted with oxygen isotopes of re-equilibrated rock-forming minerals, and the ancient hydrothermal systems driven by magmatism or metamorphism within continental orogens worldwide can be reliably quantified.

It is well known that no satisfactory demonstration has ever been given of Fermat's celebrated theorem, which asserts that the equation an = bn + cn is impossible, if a, b, c, are whole numbers, and n is any whole number greater than 2. In Legendre's Théorie des Nombres, he demonstrates the cases of n = 3, n = 4, and n = 5, the latter only in his Second Supplement. In Crelle's Mathematical Journal, ix. 390, M. Dirichlet, a mathematician of Berlin, has demonstrated the case of n = 14, but I am not aware whether his demonstration is considered successful. Legendre informs us (Second Supplement, p. 3) that the Academy of Sciences, with the view of doing honour to the memory of Fermat, proposed, as the subject of one of its mathematical prizes, the demonstration of this theorem; but the Concourse, though prolonged beyond the usual term, produced no result.

All taxa of Orthoptera known from the latest Eocene deposits of the Isle of Wight are redescribed or discussed, based on the study of their type material. The following new taxa are described: Ontogryllus gen. nov., O. rossi sp. nov. (type species), Achetomorpha gen. nov., A. irregularis sp. nov. (type species), and Proeneopterotrypus gen. nov. The latter genus is here proposed for Pteroplistes danicus Rust, described from the Palaeocene/Eocene of Denmark, as this find is important for understanding the systematic position of the genus Eneopterotrypus Zeuner. Remarks about the taxonomy of the taxa studied, age of these deposits, and ecology are given.

In the second volume of the Asiatic Researches, an extract is given from the Surya Siddhanta, the ancient book which has been long, though obscurely, pointed out as the source of the astronomical knowledge of the Brahmins. The Surya Siddhanta is in the Sanscrit language: It is one of the Sastras, or inspired writings of the Hindoos, and is called the Jyotish, or Astronomical, Sastra. It professes, as we learn from Mr Davis, the ingenious translator, to be a revelation from heaven, communicated to Meya, a man of great fanctity, about four millions of years ago, toward the close of the Satya Jug, or of the Golden Age of the Indian mythologists; a period at which man is said to have been incomparably better than he is at present; when his stature exceeded twenty-one cubits, and his life extended to ten thousand years.

Of these gigantic thermometers, with their bottle-sized bulbs, their long capillary intermediate tubes, and their upper enlarged bores for scale-reading purposes, an account of their construction and being placed in position for observation on June 26, 1879, is to be found in Part II. Vol. XXIX. of the Transactions of the Royal Society, Edinburgh, for 1879–80, and it is only proposed in the present place to give an account of their performances since that time.