ABSTRACTOur climate future depends on the delicate, fine balance of earth processes first elaborated on by James Croll, born 200 years ago in 1821. A childhood victim of the Scottish clearances, Croll, after following various indifferent occupations, managed to remove to the then rapidly industrialising city of Glasgow and eventually to Scotland's capital, Edinburgh. He blossomed as a most original, outside-the-box, thinker of great intellectual strength and modesty. He carried out scores of studies across a broad range of research topics, many related to the physical causes of climate change. He is well known for his astronomical theory of the ice ages, but should be much better regarded for his incisive physical insights into the central importance of feedbacks in the Earth system. Although humble, Croll was an ardent controversialist who strongly, perhaps over-strongly, always defended his corner. As well as his many accomplishments as a man of science, Croll was committed to exploring philosophical questions of theism and determinism, topics which occupied his earliest and last publications. A ‘top ten’ selection out of the varied subject areas that Croll tackled are explored herein, along with a brisk survey of their legacy to contemporary modelling studies and to Earth's climate future: (1) causes of climate change (1864); (2) ice-cap melt and sea-level rise (1865); (3) predicting future climates using eccentricity (1866); (4) combining orbital precession, eccentricity and obliquity (1867); (5) geological time and the date of the glacial epochs (1868); (6) geological time and denudation rates (1868); (7) ocean currents and the hemispherical temperature difference (1869); (8) feedbacks – a remarkable circumstance which led to changes of climate (1875); (9) temperature of space and its bearing on terrestrial physics (1880); (10) the causes of mild polar climates (1884).
A Comparison of some Observations on the Diurnal Variations of the Barometer, made in Peyrouse's Voyage round the world, with those made at Calcutta by Dr Balfour was read by Professor Playfair.
Synopsis Skeletal remains of Tristychius arcuatus commonly occur in ironstone nodules from the Scottish Upper and Lower Oil Shale Groups. This material is clearly distinguishable from the small shark from Glencartholm described by Traquair, Woodward and Moy-Thomas under this name. Study of the latter shows that its finspines are distinctly different from the holotype of T. arcuatus and, therefore, it has been renamed. Tristychius arcuatus sensu stricto is a medium-sized hybodont shark with a short gape, a functionally heterocercal tail and narrow-based, tribasal pectoral fins. Its most unusual feature is a well developed opercular gill cover composed of long hyoid rays. Evidence suggests that this character was present in several Palaeozoic sharks, although it is absent in all Recent elasmobranchs. It is not clear whether it was primitively present in chondrichthyans or evolved separately in several lineages. Hybodonts and ctenacanths are recognised as separate, specialised shark radiations, neither of which can be directly ancestral to Recent sharks. Of the two, hybodonts appear to be more closely related to Recent forms, although the presence of typical hybodont finspines in Tristychius arcuatus indicates that they had diverged from ancestral euselachians before the beginning of the Carboniferous.
SynopsisTwenty-eight specimens of the seed genusDolichospermahave been examined. Fourteen are assigned toD. sexangulatumLong; these possess six or seven integumental lobes which extend apically as free tentacles equal in length to the seed body except when damaged or broken off. Fourteen other specimens are namedD. pentagonumsp. nov. These are smaller and usually have five integumental lobes (less commonly six or seven). Long apical tentacles have not been seen in this species.Evidence is adduced thatAnasperma burnenseLong is the mature prothallial seed developed from the ovuleEurystoma trigonaLong.Eurystoma angulareLong sometimes possesses five integumental lobes and the free apical lobes vary in length.Compressed megaspores macerated from cupules ofStamnostoma huttonenseLong sometimes have three abortive spores in a compact group at the apex.Ovules ofEccroustosperma langtonenseLong were borne in small bunches (probably pendent) on short pedicels; one specimen of this seed shows three well-developed separate abortive spores around the apex of the functional megaspore.The cupule ofCalathospermum fimbriatumBarnard shows a structure suggesting that it may have evolved from a pair of cupules. Twelve to fourteen ovules were sometimes formed in the entire cupule though most of these were probably abortive.Some possible seed embryos are described and discussed, and an outline classification of seeds in the order Lagenostomales is proposed.
SynopsisNew collections of Zosterophyllum myretonianum Penhallow have been made at a number of localities in the Lower Old Red Sandstone of Scotland. For the first time, details of the fructification are recorded and incorporated into an emended diagnosis of the species. A comparison with the remaining species of Zosterophyllum indicates that sporangial and stalk characteristics are most important in delimiting Z. myretonianum. Tentative explanations for the wide variation in the overall morphology of the fructifications are put forward.
Synopsis The Riccarton and Raeberry Castle beds in Kirkcudbrightshire have hitherto been regarded as Wenlock in age, and the Hawick Rocks as Llandovery. Detailed mapping and revision of the graptolite faunas shows that the Raeberry Castle beds are Llandovery and the Riccarton beds Wenlock in age. On structural evidence the Hawick Rocks south of Kirkcudbright are considered to be younger than the Riccarton beds. The Riccarton beds in the area are formally defined as the Ross Formation and the Raeberry Castle beds as the Raeberry Castle Formation. Directional data suggest that the sediment forming the Raeberry Castle Formation was derived from the west and the sediment forming the Ross Formation and Hawick Rocks was derived from the north-east.
SynopsisThe zoning found in ore deposits is dominantly of two distinctive types: that in syngenetic sedimentary deposits, like the Kupferschiefer, and that in common hydrothermal deposits of either epigenetic or syngenetic characteristics. Here, epigenetic hydrothermal deposits include those commonly classified as vein, porphyry copper, contact metasomatic, and Mississippi Valley deposits; the syngenetic hydrothermal deposits are conformable, massive ores such as at Rammelsberg. The two zoning sequences, beginning nearest the source of the metals, are: in hydrothermal deposits, Fe—Ni—Sn—Cu—Zn—Pb—Ag—Au—Sb—Hg, and in sedimentary deposits, Cu—Ag—Pb—Zn.A zoning sequence represents the natural order of increasing solubilities of the metallic sulphides and other minerals in ore-forming solutions. Comparison of zoning sequences with relative solubilities in proposed ore solutions provides a rigorous test of the efficacy of such solutions. When corrected for relative metal concentrations (mass-action effect), then both theoretically predicted, and experimental relative solubilities of sulphide complexes match precisely the order of hydrothermal zoning. The order in sedimentary zoning is identical to the mass-action-corrected calculation of the sequence in which sulphides must precipitate from solutions containing metallic ions or weak chloride or hydroxyl complexes. The consanguinity of these correlations imply (1) that hydrothermal zoning is the product of deposition from sulphide complexes, and (2) that chloride complexes may be the metal-transporting agent in sedimentary deposits.
SynopsisTriradioxylongen. nov. is erected for petrified stems and petioles in which the primary xylem has a triradiate form and possesses protoxylem at the ends of the arms and in the central region. Secondary xylem is dense and composed of small tracheids having multiseriate bordered pits on all walls. Rays are narrow and high. The cortex has sclerotic nests and radial bands of fibres (sparganum structure).In the type speciesT. primaevumsp. nov. the petioles are borne 5–6 cm apart in a phyllotactic spiral of ⅓ on a stem about 1 cm (or more) diameter. The petiole is swollen at its base (about 8 mm diameter) and very gradually tapers to about 2 mm in the rachis which has not been seen to dichotomise. The length of petiole up to the first pinna may exceed 10 cm. Pinnae arose alternately and themselves branched. The T-shaped petiolar bundle has two protoxylem groups at the end of each arm and the central protoxylem divided into three in the rachis.Two detached rachises which cannot be assigned with certainty toTriradioxylon primaevumare placed in the genusLyginorachisand namedL. whitadderensissp. nov. In these the T-shaped vascular bundle is slightly larger than that in the rachises ofT. primaevumand the ends of the transverse arms are wider and may possess three protoxylem groups.The rachises in bothT.primaevumandL. whitadderensisbear alternate triarch pinna-traces but inL. whitadderensisa pair of sub-opposite monarch pinna-traces is also present.Triradioxylonis classified along withButeoxylonin the family Buteoxylonaceae placed tentatively asincertae sedisin the Pteridosperms although showing some affinity withAneurophytonin the Progymnospermopsida.
This address is concerned—not, I feel, unsuitably on this particular occasion—with the two major interests that have occupied me since I began research in marine biology following graduation at Edinburgh in 1922. Initial work on the bivalve molluscs, Mya arenaria and Ostrea edulis, at Edinburgh and Plymouth respectively, was followed by appointment as Balfour Student in the University of Cambridge and leadership of the Great Barrier Reef Expedition of 1928–29. There I made acquaintance with corals, with the reefs they form and with their associated molluscan fauna, which has since been widely extended in other regions of the Indo-Pacific and also in the Gulf of Mexico and the Caribbean in the Atlantic. It is clearly impossible to review this wide subject-matter, this address representing a statement of opinion based largely on the results of personal research.
Synopsis The stratigraphy of the Old Red Sandstone between Latheron and Brough in north-eastern Caithness has been revised. Stratigraphical subdivision in this area is primarily based on variations in lithology but is supported by the recognition of distinct faunal assemblages. The terms Wick Flagstone and Thurso Flagstone are discarded both as Group and Formation names and in their place type sequences different from those given by the Survey are proposed on the basis of the more continuous exposure seen between Ellens Goe and Latheron in eastern Caithness and in the Ham/Scarfskerry area of northern Caithness. The revision has been facilitated by an analysis of the structure of the area which suggests that a variable c . east-west compression has been the dominant controlling factor in the development of the structure of Caithness. As a result of the revision the position of the Achanarras Fish Bed is now clear. The Passage Beds Group is no longer considered a meaningful subdivision as it is partly overlain by and partly overlies this Fish Bed. The John o' Groats Sandstone Group is thought to probably overlie the Caithness Flagstones conformably. The following major stratigraphical subdivisions are recognised: D. John o' Groats Sandstone Group. C. Upper Caithness Flagstone Group ( c ) Mey Subgroup ( b ) Ham-Scarfskerry Subgroup ( a ) Latheron Subgroup. B. Lower Caithness Flagstone Group (position of Achanarras Fish Bed) ( d ) Robbery Head Subgroup ( c ) Lybster Subgroup ( b ) Hillhead Red Bed Subgroup ( a ) Clyth Subgroup. A. Sarclet Group. A typographical device is used for formal description of formations and groups whose boundaries are truncated by faults.
SynopsisHolocene carbonates rest unconformably on Lewisian gneiss in an almost land-locked bay sheltered from Atlantic waves by sand dunes: frosts are rare and cockles, the dominant species, may reach 16 years of age. Five intertidal zones are recognised: algal mat, Arenicola sand, Cardium shell sand, Lanice sand, Ensis sand. Transgressive shellbanks composed solely of cockles and linguoid in form, are advancing over the Arenicola sand towards the shore, earlier seaward positions being indicated by hard-packed areas of shell pavement. Comparison of 1973 positions with those on aerial photographs taken in 1965 demonstrates a maximum transgression of 150 m over the past eight years, but in 1948 banks were smaller and most material was onshore as a chenier.Different age-groups are dominant in different parts of the beach: young cockles high on the shore; older, partially epifaunal individuals towards low water. In any one age-group shell height is inversely related to distance from LWM. By analysing the age and growth of dead shells from the banks it is possible to estimate where they originated, and thus how much post-mortem transport they have suffered. In the centre of the bay banks receive 90 per cent of their shells from seaward, the maximum distance travelled being 400 m.During westerly gales adult cockles living high on the shore are blown seawards, though young forms escape by speedier burrowing. This, together with the concentration of oystercatcher predation on small individuals from the more emergent parts of the bay, probably explains why older animals are more abundant on the lower reaches of the shore.Feeding oystercatchers leave many conjoined valves of Cardium on the sediment surface which roll in easily with the tide and replenish the shellbanks. The valves are rarely damaged, though gulls shatter shells by dropping them onto hard areas of pavement. In calm conditions shoreward flotation of both fragments and single valves is important: banks are high and narrow, and accrete by avalanche co-sets of haphazardly arranged whole valves. In stormy conditions much comminuted shell sand is blown onto the beach from the dunes: banks are more spread out, and the shell fabric locally becomes vertically imbricate in response to directly opposed wave systems generated by refraction around the banks.
SynopsisAlderia modesta(class Gastropoda, order Sacoglossa) has a central nervous system of a type common in the Stiligeridae and Limapontiidae. The visceral loop is short and bears two ganglia, the abdominal and supra-intestinal.Medio-dorsal bodies, probably neurosecretory in function, are present on the cerebral ganglia. They were also found in eight other species of Sacoglossa and latero-dorsal bodies were noted inOxynoe viridis(Pease) andLobiger viridis(Pease).Dissections of sixteen species of Sacoglossa showed that the order may be arranged on the length of the visceral loop and the number of ganglia on it. The evolution of medio-dorsal bodies is discussed.
SynopsisKaryograms prepared from ovarian and blastoderm cells of the parthenogenetic Australian Brown Vegetable Weevil demonstrate a consistent triploid condition with 30 chromosomes which can be grouped into 10 sets of homologues. Meiosis is replaced by a single mitotic-like division in which 30 univalent chromosomes, each composed of two chromatids, divide equationally between an ootid nucleus and a single polar nucleus. Prior to the differentiation of the oocytes a peculiar bouquet stage occurs in the cells of the end chamber of each ovariole, but the significance of this phase is not known. Arrested development in eggs from individuals of low fertility is investigated and the relationship of body size and chromosome number is discussed.
SynopsisA structural profile has been constructed for part of the Caledonian fold belt from a map of the Dalradian rocks of the Loch Awe District of Argyllshire. The profile includes the Loch Awe Syncline (Bailey 1913) and the root to the Tay Nappe (Shackleton 1958). The Loch Awe Syncline is shown to be a compound syncline of F1 age, congruent with the Tay Nappe. The F1 structures are accompanied by a penetrative deformation and modified by secondary structures. The stratigraphic succession, which includes the Upper Dalradian and part of the Middle Dalradian, has been reconstructed from the profiles and is shown to have originally been about 10 km thick. The prominent features are the development of a basin to the south-east of the present area in the Late Pre-Cambrian and the extrusion of a 2 km thick basic submarine lava pile in Lower Cambrian times. A subsequent basic submarine lava sequence was extruded in Late Lower Cambrian or Middle Cambrian time and represents the topmos lithostratigraphic group yet recorded from the Dalradian of S.W. Argyll.
SynopsisThe stem,Buteoxylon gordonianumgen. et sp. nov. was found in stratified ash-beds at Oxroad Bay, near Tantallon Castle. It consists of a terminal region, about 12 cm in length surrounded by 38 petioles borne at acute angles on the stem in a ⅖ phyllotactic spiral. The stelar anatomy resembles that of aCalamopityswith a mixed pith. The petiolar bundles, however, have a distinctive T-shape in cross-section unlike any known species ofCalamopitys.Associated with this fossil stem are numerous seeds ofTantallosperma setigeragen. et sp. nov. These are radially symmetrical, with four (rarely five or six) integumental lobes joined at grooves on the body of the seed but free apically where they bear numerous bristle-like hairs. The funnel-shaped salpinx is only slightly narrower than the lagenostome. Enclosed spherical pollen grains have a trilete mark and measure 60 μ in diameter. The average dimensions of the seeds are 5·9 × 1·1 mm.
SynopsisCytological results are presented for 60 taxa of Jamaican ferns which supplement information obtained from an earlier survey (Walker 1966). A number of hybrids which form local populations and which may be mistaken for fertile species are described and illustrated. Some species complexes are examined and shown to be more extensive than previously thought. The results presented here are examined in the light of the findings of the earlier survey.
SynopsisThis paper provides a comprehensive account of the distribution of miospore species which are considered to be stratigraphically significant in the Dinantian (Calciferous Sandstone Measures and Lower Limestone Group) of the Midland Valley of Scotland. Five miospore concurrent range zones are recognised in these beds:Tripartites vetustus—Rotaspora fracta (VF) ZoneRaistrickia nigra—Triquitrites marginatus (NM) ZonePerotrilites tessellatus—Schulzospora campyloptera (TC) ZoneLycospora pusilla (Pu) ZoneSchopfites claviger—Auroraspora macra (CM) ZoneThe distribution of these zones in the sections studied provides a method of correlation in a series of rocks, which are largely of non-marine origin and notable for their lack of stratigraphically useful macrofossils and for marked variations in facies and thickness. The zones have also been proved in sections of Lower Carboniferous rocks in the Northumbrian trough, thereby providing a potential method of correlation between the two areas.Two new genera, Colatisporites and Biannulatisphaerites, are described and one Tricidarisporites emended. Fifteen new species and one new type are described, three species recombined and three emended. Representative assemblages of the miospore zones are illustrated.
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