Thin Stratum Research Articles

Shielding Errors in Critical Angle Refractometry

This paper is a mathematical and an experimental examination of the errors which may exist in critical angle refractometry when an illuminating prism is used to retain a thin stratum of a liquid sample against a measuring prism.

Geosynclinal Sedimentation in Central Gulf Region of United States: ABSTRACT

More than 30,000 feet of Mesozoic and Cenozoic sediments are present in the central Gulf region of southern United States. They constitute a great sedimentary complex (Gulf Coast geosyncline) composed of marine and deltaic deposits. The deltaic sediments occur as overlapping ladle-shaped and irregularly lenticular masses with areas of maximum accumulation (depocenters) in general parallel with the coast line. Individual deltaic masses coalesce to form elongate, geosynclinal deltaic complexes. Thin marine strata are present between the deltaic depocenters; thick marine sediments occur on the seaward edges of the deltaic masses. Landward, currently updip, both the marine and deltaic units are replaced by marginal and fluviatile deposits; seaward, the marine facies are deepe -water and the deltaic facies are more marine. Three major depositional stages are represented: a lower, marginal-deltaic stage; a middle, marine stage; and an upper, marginal deltaic stage. These primary stages coincide with major fluctuations of sea-level. Minor depositional stages and sea-level fluctuations complicate the sedimentary history of the area. Axes of maximum deposition shifted from time to time in position and alignment and progressed generally in a seaward direction. Major interruptions of the seaward progression occurred in the Cretaceous and Tertiary. The geographic positions and stratigraphic thicknesses of these depositional axes are shown on maps and cross sections. The stratigraphic and sedimentary history of the area, along with Recent geologic events, indicate that subsidence has been a major factor in creating a linear, arcuate geosyncline in the Gulf Coastal Plain of the United States. End_of_Article - Last_Page 2067------------

Relation of Dissolved Oxygen to Winter Mortality of Fish in Michigan Lakes

Winterkill of fish in southern Michigan lakes during 1944–45 provided an opportunity to study the effect of different degrees of oxygen depletion on the extent of mortality and survival of several common species of fishes. Eleven lakes were investigated. Several inches of snow cover remained on the lakes from December 11 to February 15. This abnormal persistence of snow cover was accompanied by oxygen depletion in some of the lakes to mid-winter lows occurring about February 14. The maximum concentration of oxygen in vertical series taken at about the time of greatest depletion ranged from 0.2 to above 5.0 p.p.m. in the different lakes. Where oxygen depletion was severe this maximum occurred only in a thin stratum immediately beneath the ice. Heavy winterkills occurred only in those lakes in which the dissolved oxygen was depleted to approximately 0.6 p.p.m. or less. The mortality was greatest among bluegills and largemouth bass, apparently 100 percent in some lakes. Among the pumpkinseeds, mud pickerel, northern pike, chub suckers, bullheads, and golden shiners there was a large rate of survival even in lakes where the oxygen was reduced to 0.3 or 0.2 p.p.m. No complete kill of all fish in a lake was encountered.

Subsurface Stratigraphy of the Kinderhook-New Albany Strata in Illinois: ABSTRACT

This paper summarizes the subsurface occurrence of the Kinderhook-New Albany succession in Illinois and shows the relationships of the formations and facies from place to place. A zone of relatively thinner strata extending northeasterly from the Ozark uplift divides the region into two sedimentary provinces. Southeast of this zone the succession is predominantly hard, black New Albany shale capped by the Rockford limestone. Its thickness increases southeasterly to a maximum in Gallatin and Hardin counties. Along the zone of relatively thinner strata the black shale is overlain by gray and greenish shales and siltstones in turn overlain by the Rockford limestone. In a limited area northwest of the zone, as far as Calhoun, Green, Macoupin, and Montgomery counties, the upward succession is the black Grassy Creek shale, the Louisiana limestone, the blue Maple Mill shale and siltstone, and the Chouteau limestone. The Chouteau limestone is shown to be the westerly equivalent of the Rockford limestone. Farther northwest, as far as the Kinderhook occurs in Illinois, the black shale grades upward through grayish brown into gray and blue shales, succeeded by the English River siltstone, the McCraney limestone, and the Prospect Hill siltstone. The total thickness of these strata reaches a maximum in Hancock County. There is an erosional unconformity between the Kinderhook and overlying Osage group. A number of cross sections and isopach maps illustrate correlations and changes in thickness and facies of the strata throughout their subsurface occurrence in Illinois. End_of_Article - Last_Page 915------------

Tuffs and other volcanic deposits of Katmai and Yellowstone Park

The volcanic activity in the Katmai region in 1912 took two principal forms.From the central crater of Mount Katmai great volumes of pumiceous ejecta were thrown violently into the air, and fell upon the surrounding country. Large quantities of the finer portions were carried by winds even as far as Kodiak, 100 miles away. Near the volcano the deposits are seen to form loosely coherent strata, 15 or 16 feet thick. The lumps of pumice are not of great size, two or three inches in diameter being an ordinary maximum. Mutual attrition in the air during expulsion was evidently not great, for the angles and corners are only slightly rounded. The looseness and lack of coherence of such deposits permit easy erosion, and they are not likely to be long preserved in situ, unless soon covered by more resistant beds. They may be carried out to sea and form extensive but thin strata. Because of this ease of removal and because of original wide‐spread distribution, we cannot expect that siliceous pumices, explosively ejected, will ordinarily be represented in their proper relative magnitude among the deposits adjacent to a volcano.

Northumbrian Coals

THE Fuel Research Board has just issued Paper No. 21 of the Physical and Chemical Survey of the National Coal Resources, being a report on the Yard Seam of Northumberland. The report is a very full one, and appears to be very carefully done. There is only one point to which attention may be directed. In places there is a narrow band of dirty coal at the top of the seam known locally as‘op brat’, which the report states is “sometimes known as ‘roof coal’ or ‘ramble’” From the wording of the report the reader might suppose that the term ‘ramble’ is confined to this particular coal, but as a matter of fact it is a generic term for any thin bed of shaly matter that comes down when the underlying coal is worked. Thus in the “Glossary of Terms used in the Coal Trade of Northumberland and Durham”, by G. C. Greenwell, the first edition, published in 1849, defines ramble as “A thin stratum of shale, often found lying immediately above the seam of coal. It falls down, and, getting mixed with the coals, causes some trouble to the hewer, in getting it separated and cast back.” Seeing that this brat, although described as dirty coal, is stated to have contained in one place as much as 69 per cent of ash, whereas one of the bands of shale contains only 46 per cent, it is obvious that this band might fairly come within Greenwell's definition. Perhaps the most interesting statement in the report is that the authors find “the coking properties of the seam to be weak, but not nonexistent”; seeing that Northumbrian coals are generally supposed to be non-coking, this statement is a very important one, and leads to the inference that the Yard Seam smalls may be useful for blending with more strongly coking coals in order to produce a good metallurgical coke.

An Anglo-Saxon Hut on the Car Dyke, at Waterbeach

Considerable interest attaches to the Car Dyke as it has been claimed as a Roman work by several authorities (Dr. Cyril Fox, Archaeology of the Cambridge Region, p. 179). In June of this year I attempted to make sure of the date by cutting a section through the fosse.When a well was sunk through the bank of the dyke at the Lodge, Waterbeach, many years ago, the workmen cut through a boat of some kind. It seems reasonable to suppose that this boat dates from the time when the dyke was still full of water, and had been left moored in some little creek or dock probably near a settlement site. I therefore cut a section as near as possible to the well, that is, within a few yards of the south-east corner of the Lodge. It has not been possible to complete the section or reach the bottom of the ditch owing to the wet summer. The water-level was found at a depth of 4 ft. The section, however, cut through the middle of a small dwelling on the very lip of the ditch, debris from it forming a thin stratum separating different layers of silt. From the contents of the midden which formed the floor of the hut it was evident that the site was one of the Pagan Saxon Period.

USE OF SEAWEED IN THE PREVENTION AND TREATMENT OF GOITER.*

Iodine existing on the earth in forms that are mostly highly soluble in water, the bulk of it is to be found in the sea whither it has been deposited by drainage water. In the rocks which have their origins in the sea, some traces of iodine remain and in the drainage waters flowing over and through them. This small trace diminishes in concentration as the tops of drainage areas are approached, there the soils being more thoroughly leached out. The same is true of thin strata of soils overlying impermeable rocks. Thus, higher concentrations are found in soils and drainage waters occurring nearer the ocean, although here undoubtedly drainage is only one factor as the supply of iodine is prevented from disappearing there through additions gained from sea spray blown inland. Iodine is sea water, as stated by Hayhurst in his comprehensive article,

Societies and Academies

LONDON. Royal Society, March 1.—A. Mallock: The effect of temperature on some of the properties of steel. The period of torsional vibration and the length of a steel wire were automatically and continuously recorded in terms of time, while the temperature was varied between 15° and 1000° C. The results show (1) that the variation of the rigidity of steel between ordinary temperature and a dull red heat is small (less than 1 per cent.); (2) that above the critical temperature (about 800° C.) the rigidity decreases rapidly; (3) that the temperature coefficient of expansion does not show any marked change as the metal passes through the critical temperature; but (4) that a comparison with the cooling curves of iron and steel proves that the specific heat of the high temperature form of the metal is much less than it is at temperatures below the critical point.—C. H. Lees: Inductively coupled low-resistance circuits. The oscillations in each of two circuits of low resistance coupled by their mutual inductance can be simply expressed in terms of a certain product of capacitance and inductance. The expressions for the currents lead to a simple graphical solution of the problem.—Lord Rayleigh: Studies of iridescent colour, and the structure producing it.—(1) The colours of potassium chlorate crystals. The structure of the iridescent potassium chlorate crystals investigated by Stokes and the late Lord Rayleigh is examined microscopically. The periodic twinned structure inferred by the latter is clearly shown in the photographs taken under the microscope with polarised light. Some crystals have exceedingly complex structure, showing many groups of evenly spaced twin planes and a very complex reflection spectrum. This results from high interference from twinned layers situated a considerable distance apart. Chlorate crystals, giving a silvery reflection, were obtained by Madan, who heated the ordinary colourless crystals to about 250° C. A complex twinned structure is induced, and photographs of the structure of the crystal and of the reflection spectrum show corresponding irregularities in each, resulting from want of flatness in the twin planes. (2) Mother-of-pearl. The results generally confirm those of Brewster and A. H. Pfund. Micro-photographs show the grating structure of a pearl oyster shell and the structure of parallel layers of an “ear” shell. The absorption spectrum of the latter shows that in agreement with the spacing of the layers the reflection is of the second order. (3) The colours of Labrador felspar. The colours seen by reflection arise from two distinct origins:—(a) Specular reflection from tabular inclusions, which show the colours of thin plates and are often 0.2 mm. in dimensions; they are distributed parallel to one of the cleavages. (b) Diffuse reflection from a plane about 15° away from the cleavage mentioned; this is the source of the striking colours observed. When the diffuse reflecting plane is examined microscopically under conditions which ensure that the light only comes from a very thin stratum, it is found that the plane of reflection is patchy. The patches are of irregular outline. The diffuse character of the reflection is accounted for by the small diameter of these reflecting surfaces, regarded as independent optical apertures. Their size (0·005 mm) accounts approximately for the angular diameter of the diffuse image of a point source seen by reflection. The colour of the reflection is not sharply limited to special regions of the spectrum, and can be explained by the interference of streams of light from the two surfaces of each patch. The patches may be fissures in the material, and there is evidence that their thickness is not absolutely uniform. The brightness of the colour is explicable by the large number of reflecting patches adding their effects, without definite phase relation such as would give rise to regular interference.—L. V. King: On the complex anisotropic molecule in relation to the dispersion and scattering of light.

ON THE DILATATOR PUPILLÆ OF THE HUMAN IRIS

1. The dilatator pupillas of the human iris consists of a thin stratum of radially disposed, riband‐shaped, plain muscle‐cells: this stratum covers the posterior surface of the iris‐stroma.2. At the peripheral zone of the iris the dilatator is somewhat thickened, and its cells, in place of being in a single layer as is the case over the greater part of the iris, are two or three deep.3. The dilatator is not separated from the uveal pigment by a basement membrane.4. The uveal pigment which covers the back of the iris is composed of two strata not very closely adherent to one another. The more superficial or posterior stratum, which is formed of large columnar cells, is in thin sections relatively easily detached from the deeper or anterior stratum. This last is composed of cells which are spindle‐shaped in radial sections; they are arranged over the greater part of the iris in a single layer, but here and there, especially near the periphery, may be two deep. The deeper stratum of the pigmented epithelium is intimately adherent to the adjacent layer which forms the dilatator muscle, but, at least in the adult, the cell‐elements of the two layers are differentiated from one another and do not form a part of the same tissue.

Cave-sandstone deposits of the southern Ozarks

Stratigraphy of the southern Ozarks The surface rocks of the southern Ozarks are of Ordovician, Silurian, Devonian, and Carboniferous ages. Those of Silurian age are absent over a large portion of the region, as a result of unconformities, and those of Carboniferous age are locally absent, as a result of erosion during the present erosion cycle. In southern Missouri and northern Arkansas the streams have in many places cut far below the Carboniferous rocks, leaving the older rocks exposed on the hillsides. The rocks of Devonian age consist of a thin stratum of sandstone, or of sandstone and shale, and as those of Silurian age are usually absent, practically all the rocks exposed below those of Carboniferous age belong to the Ordovician. Near the Arkansas-Missouri line the Ordovician rocks exposed along the sides of the rather deep ravines consist of manganesian limestone containing several beds that are more or less . . .

II.—On a Collection of Trilobites from the Upper Cambrian of Shantung, North China

Continuing the notice of Herr H. Monke's paper on the Trilobite-bearing limestone slabs of Yen-tsy-yai, the author observes:—The very dense and solid, slightly arenaceous limestones of Yen-tsy-yai consist of horizontal slabs (from 1–2½ cm. thick) of a dark bluish-grey colour, [p. 109] Whilst showing no traces of fossils in their interior, the limestone slabs are on one side (as shown on pl. ix) often completely covered with the remains of Trilobite carapaces, besides which are found only isolated very minute shells of Brachiopoda. Between them are here and there irregular, lengthened furrows, which may be the tracks of the Trilobites; on the corresponding opposite pails of the slabs are similarly shaped vermiform protuberances. It follows that the fossiliferous side is to be considered as the natural upper part of the slabs. In a certain number of the slabs either both sides or one only are covered besides by a thin argillaceous stratum, which equally contains, though less frequently, delicate remains of fossils; in all the other slabs the fossils present themselves en relief and often rest on a small base of limestone, and therefore convey the impression of having been originally covered by a thin argillaceous stratum, which later on was washed away by water.

PRELIMINARY STUDIES OF N. AMERICAN GOMPHINÆ

Examples of the emphasized importance of larval life better than that furnished by the subfamily Gomphinæ of Odonata are few even among insects. The nymphs live under the sediment (mostly organic debris) which falls to the bottom of ponds and streams. They are aquatic burrowers which live at such slight depth that their anal respiratory orifice is never beyond the reach of clean water. This thin stratum, which forms their home and which they only leave to transform, is one of great biologic richness. In it they have found room for development in enormous numbers and necessity for extreme specialization. They are, at least when well-grown, among the more powerful members of its teeming hidden population. The imagoes emerge, flit about under cover for a few days, lay their eggs and die. They emerge largely by daylight and are subject to great decimation of numbers at this time, and are sought later by numerous powerful enemies. The females which live to oviposit lay a very large number of eggs. A female of Gomphus fraternus laid for me in a watch glass of water over 5,000 at one time. The imagoes of the ancient genus Gomphus are regarded as a race of weaklings. Their nymphs, on the contrary, are splendidly equipped for the battle of life. And it is to the perfection of their adaptation that the prevalence of Gomphines with us is due.

1. On Galvanic Currents passing through a very Thin Stratum of an Electrolyte

If one closes a galvanic circuit containing a small battery, the electromotive force of which is not able to decompose water, and a voltameter with two platinum plates dipping into water acidulated with sulphuric acid, the current has a great intensity in the first moment, and diminishes at first very rapidly, afterwards slowly. At last its intensity approaches to zero more and more, but it never ceases completely, The more sensitive the galvanometer by which you measure its intensity, the longer the time during which you are able to observe the deflection of the needle. If the electrolytic fluid is in contact with atmospheric air, it is easy, even with a galvanometer of simple construction and moderate sensibility, to observe that at last a feeble residue of current remains, keeping a nearly constant intensity. This intensity, however, is increased by the slightest motion of the fluid, also by feeble motions produced by changes of temperature.

Notes on Pleurodus affinis , sp. ined., Agassiz, and Description of three Spines of Cestracionts from the Lower Coal-measures

Two years ago I had the pleasure of reading a paper to this Society describing a thin stratum of shale known to extend over an area of several miles, immediately above the Better-bed coal in the neighbourhood of Clifton and Low Moor, south-east of Halifax. The stratum averages from a quarter to three eighths of an inch in thickness, and is almost entirely composed of the fragmentary remains of fishes and Labyrinthodonts. Between thirty and forty species of fishes have been found, and are enumerated in the paper already referred to.

3. Note on the Effect of Heat on Infusible Impalpable Powders

Several years ago Professor Dewar gave me a specimen of silica in a state of exceedingly minute division, which had been produced in Dr Playfair's laboratory in the preparation of fluosilicic acid. I noticed at the time how much its great mobility is increased by heating—so that it behaves almost like a liquid. And I fancied that I observed close to the surface a thin stratum of what might by the same analogy be called a vapour; consisting of particles thrown up and falling back again, like the little drops thrown up at the surface of soda-water. I was inclined to ascribe these phenomena to heat directly—supposing that the particles were fine enough to behave, though in a very imperfect way, as the kinetic theory assumes the particles of a gas to behave.

I. On the induction of electric currents in an infinite plane sheet of uniform conductivity

1. When, on account of the motion or the change of strength of any magnet or electromagnet, a change takes place in the magnetic field, electromotive forces are called into play, and, if the material in which they act is a conductor, electric currents are produced. This is the phenomenon of the induction of electric currents, discovered by Faraday. I propose to investigate the case in which the conducting substance is in the form of a thin stratum or sheet, bounded by parallel planes, and of indefinite extent.

On the Occurrence of Remains of Eurypterus and Pterygotus in the Upper Silurian Rocks in Herefordshire

D uring a recent visit to Herefordshire I was fortunate enough to discover a great number and variety of Crustacean remains belonging mostly to Eurypterus and Pterygotus , the former predominating, some portions of which may perhaps differ from any yet figured and described—though my friend Mr. Woodward, to whom I have sent them for examination, is inclined to think that there are no new species among them. Their abundance and excellent state of preservation makes the discovery of interest, because I believe none have yet been found anywhere in Palæozoic rocks in England so perfect or well preserved. The remains consist for the most part of considerable portions of the body (the largest measuring a little more than 1 inch in breadth near the middle of the body, and two and a quarter inches in length without the head or tail, which are wanting) with attached body-rings and other appendages but having neither head nor tail, single body-rings of large size, detached heads, thoracic segments, tails of Eurypterusterus megalops , swimming-feet, claws, &c. Many might have been obtained entire, if the thin stratum in which they occur could have been worked; but from its position it was impossible to procure anything but detached fragments (though every piece of shale was crowded with them), so that the Crustacea were invariably broken, and I fractured many entire specimens in consequence. They are of a uniform brown colour, while those from Lesmahago, in Scotland, are always black, and are of the identical colour of the altered Silurian formation

On the Lignite Mines of Podernuovo, near Volterra

Abstract T he author stated that the deposit of Lignite at Podernuovo, near Volterra, is of lacustrine origin, and consists of two parallel strata of compact coal about 2.5 (=8 feet 4 in.) in thickness, separated by a thin stratum of marl, with marsh-shells. The lower coal-bed lies on a bed of marl with marsh-shells, and the upper bed is covered by a marine formation belonging to the Upper Miocene. The lignite comes to the surface near the Alberese, where it is thrown up in a large mass and extends for a considerable distance. In the Monterufoli valley, where the lignite is worked, its inclination is found to be about 42° at a depth of 40 metres, where it is intersected by an adit-level driven from the surface of the hill for the removal of the lignite. Two galleries have been driven at right angles to this to a distance of 120 metres right and left through the lignite. Some shifts occur bringing the upper bed down nearly to the level of the lower one; the inclination of the beds diminishes gradually; and the intervening stratum of marl decreases in thickness, and probably at last thins out altogether. The coal in the upper bed is better than that in the lower one. The author remarked that this lignite deposit differs from those of the neighbouring valleys (such as the Val di Bruno, Val di Pecora, Yal di Cornia, and Val di Cecina), in being purely of marsh origin, while they are estuarine.

On the change of refrangibility of light

The author was led into the researches detailed in this paper by considering a very singular phenomenon which Sir John Herschel had discovered in the case of a weak solution of sulphate of quinine, and various other salts of the same alkaloid. This fluid appears colourless and transparent, like water, when viewed by transmitted light, but exhibits in certain aspects a peculiar blue colour. Sir John Herschel found that when the fluid was illuminated by a beam of ordinary daylight, the blue light was produced only throughout a very thin stratum of fluid adjacent to the surface by which the light entered. It was unpolarized.