James Croll's Physical Theory of Secular Changes of Climate emerged during an age of revolution in geology that included the rise of the glacial theory and the search for its underlying causes. According to Croll, periods of high eccentricity are associated with the persistence of long glacial epochs, within which glaciations occur in alternate hemispheres when winter is at aphelion every ~11,000 years; however, astronomical forcing is only able to produce glaciation by means of physical agencies (climate feedbacks) that amplify the small effects of varying seasonal irradiation. Croll understood the importance of interglacial deposits because they provided evidence for the occurrence of multiple glaciations within his long glacial epochs. He was aware of the limitations of the terrestrial record and suggested that deep-sea sediments would contain a continuous succession of glacial-interglacial cycles. Contrary to a widespread view, however, Croll was not envisaging the advent of palaeoceanographic exploration avant la lettre, but instead was drawing attention to the inadequacy of the land record as a testbed of his astronomical theory. Yet, the marine record did eventually deliver a test of astronomical theories almost exactly 100 years after the publication of his 1875 book Climate and Time in their Geological Relations. Here, we provide an historical account of the technological and scientific developments that led to this and a summary of insights on astronomically paced climate changes from marine, terrestrial and ice core records. We finally assess Croll's ideas in the context of our current understanding of the theory of ice ages.

The ontogeny of the pelturine olenid trilobite Leptoplastides salteri (Callaway, 1877) from the Shineton Shales, Shropshire, England, was first described in 1925 by Frank Raw. Since that time, scanning electron microscopy and other new technologies have revealed many more details of structure, of early developmental stages in particular, than were available to Raw. Whereas protaspides are not preserved and the state of preservation is less than perfect for the smallest meraspides, we have established that the latter had an array of delicate, long thoracic and pygidial spines, as well as paired procranidial spines, which disappear by meraspid degree 8. Raw's reconstructions of early meraspides, and his measurements of the early stages in development, are here amended in the light of new information. Dorsal spines in the adult are much more highly developed than have been documented in any other olenid. The hypostome is preserved in place in several specimens. Initially conterminant (attached to the doublure), it becomes natant (free) in late meraspid to early holaspid stages of development, with its anterior contour fitting exactly to that of the glabella. The ecology of the widespread Leptoplastides is best known from very extensive sections in South America, which provide a useful basis for comparison. It was well adapted to a range of environments, both oxygenated and dysoxic, and is usually the dominant taxon in the biofacies in which it is found.

The Carboniferous lungfish genus Sagenodus is reviewed from all available British specimens and described in detail for the first time. We identify two species exclusive to the UK: Sagenodusinaequalis, the type species, deriving from the late Carboniferous (=Pennsylvanian); and Sagenodus quinquecostatus derived from the early Carboniferous (=Mississippian). The genus is probably the most widespread of the known Carboniferous lungfish genera, but the British species have not been formally described since their discovery in the mid–late 19th Century. This work will provide data to help resolve existing questions about the position of Sagenodus in the phylogeny of Palaeozoic lungfishes, and provide a template for the recognition of isolated elements in museum collections and the finds from recent and future field work. The early Carboniferous species, S. quinquecostatus, shows a so far unique functional mechanism in which the lower tooth plates appear to rotate relative to the upper plates during jaw closure, implying a kinetic function at the symphysis or jaw joint.

There were seven Turbellaria in the material handed to us by Mr W. S. Bruce, all obtained in April 1903 from Scotia Bay, South Orkney Islands (9–10 fms., Station 325, lat. 60° 44′ S., long. 44° 51′ W.). Their occurrence is interesting, as, although Studer (Ueber Seethiere aus dem Antarktischen Meere, 1876) mentions, without adequately describing it, a Eurylepta from Kerguelen Island, there are no definite records, so far as we have been able to ascertain, of Turbellarian species from nearer the Antarctic than the coasts of South America.

All observers are agreed that the bones of the plastron and some bones of the carapace are simple membranous bones, arising from centres formed in a pre-existing fibrous membrane. Considerable difference of opinion exists as to the development of the costal and neural plates of the carapace.

Owen speaks of the ossification “as extending from the ribs and neural spines into the substance of the neural and costal plates. The ribs and spines enter into the composition of the carapace.”

Gegenbaur questions whether the ribs of the Chelonia “are not in reality enormously developed transverse processes, and considers that the neural and costal plates have developed in the integument.”

Claus remarks that the spinous processes of eight of “the thoracic vertebræ (2nd to 9th) appear in the middle line as horizontal plates (neural plates), the ribs of the same vertebræ are transformed into broad transverse plates (costal plates).”

Huxley says that the neural plates and the costal plates exist as expansions of the cartilages of the neural spines and ribs of the primitive vertebræ, before ossification takes place. This being the case, the “neural and costal are vertebral and not dermal elements, however similar they may be to the nucleal, pygal, and marginal plates.”

There is no branch of natural science about which we know so little as that which relates to the structure of crystalline bodies. By assuming the form of an integrant molecule, crystallographers have found no difficulty in building those geometrical solids which minerals and artificial crystals present to our observation. They conceive that these molecules unite by their homologous sides in the formation of the primitive crystal, and by supposing that they arrange themselves in plates on the faces of that crystal, each plate successively diminishing in size by the abstraction of a certain number of these molecules in lines of a given direction,—all the secondary forms of the crystal may be easily deduced.

In a new investigation of this kind it is always desirable to repeat the observations under as many conditions as possible. The variables are so many that with a limited experience it cannot be expected that the subject will be exhausted, or that the conclusions arrived at from early observations will be in all cases confirmed. As an opportunity offered in the beginning of 1890 for repeating the tests made the previous year on the amount of atmospheric dust at different places on the Continent, it seemed desirable that the old ground should be gone over again rather than that the investigation should be extended to new areas. The observations made in this country have also been confined to the same stations as in 1889; and in this paper I intend giving the results of a series of tests repeated at the same stations, at about the same dates, but under the conditions existing in 1890, as has already been given for 1889 in Part I. of this subject.

The distribution and zonation of Chthamalus stellatus and Balanus balanoides on British coasts is reviewed, and it is shown that the very sheltered waters of Loch Sween and West Loch Tarbert are unusual in that Chthamalus occurs there in greater quantity than in any other sheltered (British) locality, and the upper limit of Chthamalus is consistently higher, relative to other species, than elsewhere in shelter. The lower limit of Chthamalus is generally at a rather high level on these shores even when bare rock occurs below. Balanus balanoides, on the other hand, is often scarce or absent at the same sheltered sites. The physical conditions in the lochs (water temperatures, tides, winds, sunshine, rainfall) and their seasonal variations are examined and it is shown that there probably is a unique succession of environmental factors that would favour Chthamalus and operate against Balanus at critical times of the year. It is suggested that Chthamalus occurs higher than Pelvetia in the lochs because of a greater tolerance of irregular and often prolonged periods of desiccation. The failure of Chthamalus to occupy the middle and lower shore when Balanus is absent indicates that competition between the two barnacles does not alone determine their vertical distribution on the shore. A tentative hypothesis is developed showing how the very local distribution of Chthamalus and the level occupied on the shore might be related to responses of the cyprids to light and to a supposed requirement of emersion during the early stages on the shore.

The Quadrature of the Conic Sections, and the Computation of Logarithms, are problems of considerable importance, not only in the elements of Mathematics, but also in the higher branches of that science. On this account, every successful attempt to simplify their resolution, as well as any new formulæ which may be found applicable to that purpose, must always be interesting, and must in some measure contribute to the improvement of mathematical knowledge.

In this paper I shall first refer to the circumstances under which the following observations were made.

I had gone in the autumn of 1856 for a few weeks to Elie on the Fife coast, and was induced, as a means of relaxation and exercise in the open air, to pay some attention to the geology of the neighbourhood, resuming for a brief interval what was once a favourite pursuit. About a mile to the east of the village, I found a stratum well deserving attention—a thin bed of limestone—dipping inland a little beyond the cliff on which stands the ruined Castle of Ardross. The fossil shells which it contained were of unusual form, and beautifully preserved; there were fish remains of two or three species, and a small group of crustaceans still more remarkable. Among the fish I thought I could detect the large scales of an Irish species—the Holoptychius Portlockii—and among the crustaceans there were the valves of Dithyrocaris, a genus particularly characteristic of the Irish beds. At once the question arose whether these fossils might not serve as links connecting this Ardross bed with the Irish series. The point was of the more importance, that our leading geologists had been differing widely as to the true position of our Scottish coal strata in the geological scale. The lamented Professor Edward Forbes had assigned them a place comparatively high, while Sir Roderick Murchison, with surer judgment, had taken the opposite view and put them beneath the Newcastle coal-field.

If it be true that “there is a history in all men's lives, figuring the nature of the times deceased,” how much more worthy of record the lives of those who have left an impress upon their age, who have corrected popular errors, have made clear much that was obscure, and, from the force and fulness of truth in them, have become the great teachers of their time. The histories of such lives figure more than the “times deceased,”—they teach us how to occupy our time; and though these earnest men are dead, their works are yet living epistles, ever speaking to those “who have ears to hear.”

Having undertaken to continue the observations on the growth of trees commenced by my father in 1878, and carried on by him with unflagging zeal until a few months before his death in 1882, I give in the present paper the measurements made by him in 1881, which he did not live to publish, and those made in 1882 by myself. I shall also endeavour to point out the conclusions which may be drawn from the whole series of observations, beginning in 1878, arranging them under the heads of—

I. Annual Observations.

II. Monthly Observations.

III. Influence of Weather on the Growth of Wood.

In the year 1811, when I was occupied in drawing up an article on Burning Instruments for the Edinburgh Encyclopædia, my attention was in a particular manner directed to the construction of Large Lenses, and to the different methods by which they could be combined with plane and spherical mirrors, for the purpose of obtaining an intense heat from the concentration of the solar rays. I was thus led to examine the inventions and contrivances which had been previously proposed by others, for accomplishing the same object; and after giving a historical account of them, I proceeded to describe the improvements and constructions which had occurred to myself.

I have thrown together, in this chapter, the ores of several members of a family of the elements, which may be called the family of the magnetics;* and I have also, from its frequent chemical association with iron, placed titanium along with them. No attempt was made by me to analyse the ordinarily-employed iron ores, but only such as, from their apparent purity, or from the excellence of the specimens, appeared to be of mineralogical interest.

The present inquiry is closely connected with some of the phenomena presented in golf:—especially the fact that a ball can be “jerked” nearly as far as it can be “driven.” For this, in itself, furnishes a complete proof that the duration of the impact is exceedingly short. But it does not appear that any accurate determination of the duration can be made in this way. Measurements, even of a rude kind, are impracticable under the circumstances.

In 1887 I made a number of preliminary experiments with the view of devising a form of apparatus which should trace a permanent record of the circumstances of impact. I found that it was necessary that one of the two impinging bodies should be fixed:—at least if the apparatus were to be at once simple and manageable. This arrangement gives, of course, a result not directly comparable with the behaviour of a golf-ball. For pressure is applied to one side only, both of ball and of club; but when one of two impinging bodies is fixed it is virtually struck simultaneously on both sides.

M. De Luc, in his Idées sur la Météorologie, has made some objections to the Theory of Rain which I had the honour to lay before this Society. I shall now endeavour to answer these objections; and hope the Society will forgive me for taking up a little of their time and attention with this subject. The reputation of M. de Luc is so well established in the republic of letters, that I must not neglect remarks which have the fanction of such authority; although, in the present case, they appear to me to have come from a judge who was too much preoccupied with a different system.

As the reputed fact of Archimedes having burned the Roman ships engaged in the siege of Syracuse, by concentrating on them the solar rays, has not only been doubted but disbelieved by some of the most eminent scientific men, I shall briefly give the evidence on both sides.

The burning of the ships of Marcellus is mentioned by most of the ancient writers who refer to the machines which Archimedes employed in the defence of his native city, and their statements have been repeated by succeeding authors, without any doubts having been expressed until comparatively recent times. Our earliest authorities on the subject are Diodorus Siculus, Lucian, Galen, Dion, and Pappus.

The title which I have given to this paper, is, perhaps, faulty, and apt to lead the imagination to expect a description of the various forms of those sea-weeds which clothe the channel of the deep;—the arrangement of the species, as depending on the soil and depth of water, the food which they yield to the various creatures that browse upon them, and the protection they afford to such as take refuge among their leaves and branches. Very different, however, is the scene which I propose to describe,—a bed of peat-moss, covered by the sea at every full tide, but indicating, by the appearances which it exhibits, that its present low level is different from its original position. In other words, it is a geological phenomenon, occurring in the Frith of Tay, similar to the one observed on the Lincolnshire coast, which, in 1796, was examined by the late Sir Joseph Banks and Dr Joseph Correa de Serra, and described by the latter in the Transactions of the Royal Society of London for 1799, p. 145, under the title, “On a Submarine Forest, on the East Coast of England.” I venture to prefix the same title to this paper, which I now offer to the consideration of the Royal Society of Edinburgh, aware of its impropriety, but urged by the wish to connect similar phenomena by the common terms employed in their description.

The common forked setæ which constitute the ventral setal bundles in the Naididæ possess, like the simple setæ of many of the earthworms, a slight swelling on the shaft, the so-called nodulus. The setæ themselves are the principal organs of locomotion, being used as levers, which obtain a hold of the substratum by means of their hooked and forked distal ends; and besides being movable in an anteroposterior direction they are capable of some degree of protrusion and retraction. The position of the nodulus on the shaft is held to regulate the distance to which the seta can be protruded; though it can be retracted so that the nodulus is below the level of the epidermis, it cannot be protruded beyond that degree which brings the nodulus level with the surface.

Soil conservation on the Loess Plateau is important not only for local residents but also for reducing sediment downstream in the Yellow River. In this paper, we report a decrease in soil erosion from 2000 to 2010 as a result of the ‘Grain for Green' (GFG) Project. By using the Revised Universal Soil Loss Equation and data on land cover, climate and sediment yield, we found that soil erosion decreased from 6579.55tkm–2yr–1 in 2000 to 1986.66tkm–2yr–1 in 2010. During this period, there was a major land cover change from farmland to grassland in response to the GFG. The area of low vegetation coverage with severe erosion decreased dramatically, whereas the area of high vegetation coverage with slight erosion increased. Our study demonstrates that the reduction in soil erosion on the Loess Plateau contributed to the decrease in the sediment concentration in the Yellow River.