Rapid Stream Research Articles

THE OBSCURE PHYSIOLOGY OF POSTSTENOTIC DILATATION: ITS RELATION TO THE DEVELOPMENT OF ANEURYSMS

A mass of fluid ejected through a narrow and limited constriction under high velocity strikes against a more slowly moving mass of fluid distal to the stenosis resulting, first, in the conversion of high kinetic energy into high potential energy or lateral pressure and, second, in the lateral deflection of the rapid stream and even in a complete reversal in its direction of flow, thus resulting in a clash of opposing streams that produces eddies of alternating high and low pressures whose repeated impacts over a prolonged period against an elastic wall are capable of inducing structural fatigue and distention of that wall. Accentuating the play of these forces is a third factor: the hydraulic principle that a widening stream causes decreasing velocity which in turn produces increasing lateral pressure. The resulting interplay of these three factors recurring repetitively with each systole in a pulsating stream, and operating in a limited segment of an elastic vessel, produces eventually and inevitably the phenomenon of poststenotic dilatation. It is a highly intriguing thought that this sequence of events may be the initiating and possibly the most important factor in the development of the fusiform dilatations, the saccular aneurysms, or even of the dissecting aneurysms commonly observed in the arteriosclerotic aorta in which segmental atherosclerosis or fibrosis may produce a localized or relative stenosis. The recognition of the potential power of the hydraulic forces liberated beyond a real or relative stenosis may assist in the explanation of the destruction of bone and surrounding structures that occasionally accompanies the development of a thoracic aneurysm. They explain also the aneurysmal dilatation of the vein usually seen at the site of an arteriovenous fistula where the arterial stream under high pressure and high velocity is ejected through an abnormal communication into the widened bed of the accompanying vein. The occasional aneurysmal dilatation of the pulmonary artery in the presence of a patent ductus may also be ascribed to the hydraulic forces liberated when the arterial stream of high pressure and high velocity is ejected from the narrow ductus into the wider and less rapidly flowing stream of the pulmonary artery with its lower pressure. It is highly probable, also, that the sudden cerebral hemorrhage attributed to the rupture of a small aneurysmal dilatation has its inception in the precipitate unleashing of hydraulic forces suddenly augmented by the heightened pressure and increased velocity of flow incident to emotional stress or physical exertion. Similarly, sudden death from rupture of a larger thoracic or abdominal aneurysm may follow the sudden increase in blood pressure and pulse rate that accompanies emotional stress or physical exertion and produce an increase in neocity of flow which greatly augments the play of hydraulic forces, with resulting sudden increase in lateral pressure just distal to the junction of the narrow arterial lumen with the greatly widened bed of the aneurysmal dilatation. These and other similar vascular phenomena may find their proper explanation in the application of the hydraulic laws that govern the pulsatile flow of fluid through a system of elastic vessels subjected to real or relative narrowing by congenital abnormalities, by degenerative processes, or by accidental injuries. They give stern warning also of the need to employ, in vascular surgery, methods of end-to-end anastomosis that permit growth at the site of union as the child grows, thus avoiding future stenosis, and methods that prevent or minimize the development of constriction at the site of anastomosis, either by puckering at the time of operation, or by cicatricial contracture as healing progresses. Grateful acknowledgment is hereby accorded to Professor J. K. Vennard of the Department of Civil Engineering at Stanford University for his helpful advice and criticism, and to Drs. Ernest Schnoor, Eldon Ellis, and Iseu da Costa, fellows in surgery, for their invaluable help in executing the experimental studies presented in this paper.

SOME PROBLEMS ON THE DISTRIBUTION OF FROSTDAMAGE

(1) On 9th May, 1952, there was a destructive frostdarnage in Fukushi-ma prefecture. A few parts in this prefecture suffered additional frostdama-ges vocally on 17th, 22nd, and 26th, May. (2) 3.n the Fukushima Basin mulberries, pears and peaches only sufferd the first frostdamage of the year. The distribution of several grades on in mulberrydamage is mapped in Fig. 1. The distribution of “Super high” and “high” grades is found in two belts; one is in the flood-plain of River Abukuma situated on the north-eastern lovvest part of the basin, and the other on the gentle slope of the young compound fans in the south-western part of the basin. The pattern of this distribution relates closely to that of the minimum temperature, since the time of mulberries germination. is almost similar th rdughout the basin floor. The form er is so. low in its height that cold air settles early in the morning, and the latter is a stagnant part of the cold air, caused by windbreaks maide of dense cryptimerias and bamboos, and by other reasons. (3) The distribution of frotdamage in Fukushiia prefecture. In the Abukma valley, and on the Abukuina plateau, or Nakadori, there is almost always a tendency of suffering severer frostdaznage than in Aizum and Hamadori. Although the minimuin. temperature is lowest in the south-wastern part of the prefecture there is no frostdamage of mulberries untill early in May. Since Aizu is a mountainous, snowy province, mulberry buds are later than in the other pprovinces, and there is also few frostda-mage in April and early in May. In Hamadori or the littoral province it is as warm as in the Fukushima Basin, but the littoral has longer frostless period owing to oceanic influences. In spring, 1952, and 1941, etc, the middle Abukuma valley and. the plateau suffered severe damages, while there Little or no daiiiage in the gorge and its outlet on the south-easten manin of the Fukushima Basin. since the Surimagi and Okawa Valley also have gorges at the lower parts, and bear some resemblanees to the middle hukilnza Valley, severe frostd.ainage sometimes occurred in the upper part but a little or no frostdauiage occurred in the gorge and its outlet. (a) In the gorge the canyon wall is so steep that the Katabatic wind hlows as soon as tre air cools down. By the drainage of the speedy air, the cool air mingles with the warmer air of the upper. layer. (b) cold airsaagniates on, the Wide, gentle slope of the upper valley, and through a narrow steep floor of the gorge, it is drained off as fast as a rapid stream in the canyon. it mingles With. warm. air, and they blow down towards a gorge outlet. That is one of the reasons why frostdamage is not so severe in the gore and its outlet. (4) On the flood-plain of the Abukuma-River in the Fuku sima Basin, the frostdamage occured in 33 years out of 52 years from 1889 to 1941. Among these 33 years, very great damages were made in 9 years. In spite of the frequent damages one of the most integrated sericuture region of Japan, located on the flood-plain in north-eastern Ft kusinia Basin did not move towards a frostless region on. the slope of its surrounding mountain. Where the latest frost occurs in June or at the latter part of May, silkworms of summer or autumn are mainly reared. (5) The method of protection front frostdainage is has made no progress in this region. The difficulties of prevention increased rather than before the war owing to the dispersion of mulberry fields, resultedf rom the expansion. of fields for food production during the wartime, and to other various reasons. Whereas such sensitive crops, as pears and some sort of vegetables came to be raised. in the re ion where the damage e was repeated in almost every season, thus resulting in suffering severer damage. (6) With a few e ceptions. the people are not adequately utilizing the frmtle s belts of a temperate zone on the slope of surrounding mountains and of isolated hills.

Biogeographic and Taxonomic Studies in Atopsyche (Trichoptera, Rhyacophilidae)1

The genus Atopsyche is a small group of rhyacophilid caddisflies containing about twenty species. It is confined to the warmer areas of the Americas, ranging from southern Texas and Arizona to northern Argentina. Information to date indicates that the larvae occur only in clear, cold, rapid streams, usually spring fed, a relatively infrequent habitat throughout the range of the genus.

The Changing Hydrologic Pattern of the Renton-Sumner Lowland, Washington

THS CHANGING HYDROLOGIC PATTERN OF THE RENTON-SUMNER LOWLAND, WASHINGTON John O. Dart Portland State College One of the earliest regions of farm settlement in the Puget Sound Trough, the Renton-Sumner Lowland, has been an area of historic conflict in the nomenclature of its streams. This situation has developed because of several major changes in the drainage pattern, all of which have occurred in modern times within a relatively limited area. Th« lowland is a north- south trending glaciated trough approximately twenty-five miles long and two to three miles wide parallel to the sound and separated from it by a narrow strip of rolling upland. This western upland along and a similar one to the east serve as sharp physiographic boundaries. On the north the valley is terminated by the shore of Lake Washington and in the south it merges with the westward trending Puyallup Valley. This region is a pre-glacial stream channel which has been deepened and widened by the Puget Sound lobe of the Cordilleran ice sheet. As the ice retreated, lakes and streams fed by melt-water deposited a thick layer of sediments , leaving a wide, flat floor, modified in minor respects by thepost-glacial streams. The present rivers of the lowland include the Cedar, the Green, and the White. Cedar River heads in Cedar Lake on the western slopes of the Cascades , off map 1 to the east. Under natural conditions this would provide a steady flow, but the lake provides Seattle's water supply, and the volume decreases during the summer months. Reaching the valley at its northern end, the Cedar has constructed an alluvial fan which formed the original site of Renton. Fed by a number of small streams high in the Cascades near Stampede Pass, the Green River has a steep gradient and has cut a deep gorge in the hard rock formations well to the east of map 1. Below this point it flows through the folded structure of the Puget Group and the glacial drift of the plateau, reaching the lowland northeast of Auburn. With their sources at Emmons, Frying Pan, and Winthrop glaciers, the east and west forks of the White River converge on the north elopes of Mt. Rainier , while the main tributary, the Greenwater, drains the western flanks of the Cascades well off map 1. The White enters the trough east of Auburn and the town is built on the fan formed by the aggrading stream. Prior to 1906, the two major streams of the lowland, the Green and the White, entered the valley within a short distance of each other and both flowed lorthward, the Green joining the White about a mile northeast of Auburn. Durng floodtime , the White would occasionally spill a small portion of its volume nto the Stuck River, a shallow distributary which carried its waters southward nto the Puyallup River, just south oí Sumner. The flow was never long enough tor in sufficient quantity to develop a well defined channel through the low swampy iasin. At the southern extremity the floor of the lowland rises sharply, built ip by deposition from the Puyallup. During this sedimentation, however, there ras sufficient volume from the Stuck to maintain the opening into the Puyallup· After receiving the waters of the Green, the augmented White River conlnued to flow northward, meandering widely over the flat valley in a channel 5-20 feet deep between well developed natural levees. Just west of Renton 20 Yearbook of the Association VOL. 14 lAKt SEATTLE WAiHittere* TACOMA mam STREAM PATTERN BEFORE HOÉ, ..... LCAVLAND BORDER 1952 of Pacific Coast Geographers 21 LAHt STATTLE WAtHIfCTtM ENTOM D STREAM PATTERN SINCE ? 17 LOWLAND BORDER to mu* ? 22Yearbook of the AssociationVOL. 14 the river cut into the valley side and flowed through a narrow gap to Elliot Bay. At the point where the river left the lowland it was joined by the Black River, a narrow rapid stream which was the outlet for Lake Washington. Its depth varied from a few inches to several feet, regulated by the waters of the lake and the Cedar River which flowed into it from the east. As the Black entered the White, the latter became...

千曲川カジカの生態調査

Cottus pollux Günther cannot live in some parts of Chikuma River on account of the polluted water or lack of the water caused by power plants. Its breeding in this river occurs from early February to the middle May, and the temperature of water during the season stands 4.0-10.5°C at 10 a. m. The eggs are laid under the flat stones in the rapid stream. The number of the eggs one fish contains is in proportion to the body length, and the breeding is done about 3 times during the season. When the body is 10.5 c.m. long on the aw average, it breeds about 300 eggs a time, and the diameter of the eggs laid under the stone is 2.9-3.3 m.m. The color of the eggs is mostly light orange.

鴨川に於ける水棲昆蟲特に毛翅目幼蟲の季節變化

The seasonal change of the insect fauna of rapid stream was carried out during a year from December 1947 to Jauuary 1949 in the River Kamo in Kyoto. The insect larvae fluctuated in two maximal population densities in a year, the first occurring from May to June or often July and the second in September or October. Among the caddis-worms, the larvae of both Stenopsychidae and Hydropsychidae showed two maximal occurrences in a year. The larvae of the former family were most abundant in every seasons, their greater populations being found in May-June and August, while those of the latter family were much fewer in numbers than in the former, being found in the greatest abundance in March-April and September. On the contrary, Goera and Glossosomatinae have only a single maximum density in a year. Both of the groups were not found in midsummer. The periods of most abundant. occurrences of the species which belong to those groups overlap one another (fig. 4).

A Non-Fouling Hydrogen Liquefier

A description is given of: (a) the construction and operation of a complete throttle expansion hydrogen liquefaction cycle employing the Kapitza circuit for operation with ordinary commercial gas without fouling of the heat exchangers by low freezing impurities; (b) a simple scheme for employing ``dry ice'' as a supplementary precooling agent which effects a considerable saving in the amount of liquid nitrogen used by the liquefier; (c) a satisfactory method of soldering together a Kapitza side-by-side multiple tube interchanger; (d) an efficient and easily built combination heat exchanger and trap for freezing out water and oil vapor from large, rapid streams of compressed gas.

Catskill facies of New York State

The Catskill facies of continental sediments consists principally of graywackes interbedded with conglomerates and of red sandstones and shales with a small percentage of green and dark shales and massive conglomerates. The Catskill sedimentation was introduced in early Hamilton times and represents a great series of alluvial-plain deposits laid down upon the land surface at the base of the re-elevated Taconic Mountains and grading into the sediments of an inland sea. The red shales are interpreted as flood-plain and deltaic subaerial topset beds into which the graywackes of the alluvial plain graded. Continental conditions of deposition were exaggerated as the Upper Devonian progressed, for the Katsberg beds in the east are increasingly conglomeratic. The Catskill deposits are characterized by the extreme angularity of the grains of the sandstones. The pebbles of the conglomerates, on the other hand, are well rounded. Barrell contended that the Catskill sediments were derived in the main from the western limits of the old Appalachian landmass, thus placing the source rocks to the southeast and east in an area now covered by Connecticut coastal plain deposits. The present author disagrees with this viewpoint and claims that the sediments had their origin in a near-by source to the north and east. The Taconic Mountain area is the most likely source, for it is situated in a suitable location and contains metamorphic rocks and quartz veins of similar character to the grains making up the graywackes and conglomerates. Moreover, sufficient evidence from structural considerations can be adduced to support strongly the hypothesis that orogenic forces were active in the Taconic area during Middle to Late Devonian. In early Hamilton times the first orogenic movements began. These raised western New England above the shallow early Devonian seas and started the cycle of continental deposits. Short, rapid streams carried large amounts of detritus from the highlands and dumped their loads quickly on emerging upon a flat shore at the base of the mountains. Gradually an alluvial plain was built out and as the sea moved back, due both to further uplift and to the deposition of alluvial materials, an intermediate zone of flood-plain and delta materials developed between the alluvial plain and the sea. In this intermediate zone were deposited the red sediments that gave rise to the red beds. As time progressed, the shore line varied as did the depositional zones. Periods of quiescence or aridity moved the red-bed zone closer to the foot of the mountains, while renewed uplift increased the area covered by the coarse, angular deposits. Orogenic movements continued throughout the Upper Devonian with increasing vigor. There is no evidence to indicate an arid climate during the Middle and Upper Devonian, and the abundance of plant remains in the graywackes suggests a temperate climate with moderate but seasonal rainfall. . . .

Societies and Academies

PARIS Academy of Sciences, July 30 (CM., 199, 329-392). GEORGES CLAUDE:—A floating Claude-Boucherot installation. D'ARSONVAL: A visit to the Tunisie. Remarks on the Claude-Boucheret installation for utilising the thermal energy of the sea. NATAN ARONSZAJN: Dirichlet's series with linearly independent exponents. EUGENE REMES: The effective calculation of Tchebitchef's polynomials of approximation. STEFAN BERGMANN: Integral and meromorph functions with two complex variables. GEORGES ALLARD: A general method of statistics applicable to indiscernible particles. A method for obtaining the law of statistical distribution of the molecules of a gas. This is an extension of Planck's method, ‘ and allows a closer analysis than the methods of Bose-Einstein and of Fermi-Dirac. PIERRE LEJAY: Gravity observations in Malaya, the Dutch Indies, Cambogia and Cochin China. Proof that work done with the Holweck-Lejay pendulum is in close agreement with that of Vening Meinesz. D. G. DER-VICHIAN: Polymorphism in the monomolecular layers of fatty acids at the surface of water. THEODORE KAHAN: The thermal variation of the structural demagnetising factor in nickel and cobalt. The existence of the structural demagnetising field in nickel and cobalt is confirmed by evidence of its thermal variation. The factor of this field decreases as the temperature rises. MORICE LETORT: The kinetics of the thermal decomposition of the vapour of acetaldehyde. The true order of the reaction, derived from the initial data, is 1-5: a higher value, approximately 2, results from the wall effect. WILFRIED HELLER: The coagulation of hydrophobe sols by freezing in relation with mechanical coagulation. ANDRE DE PASSILLE: Study of the dissociation of the ammonium phosphates. Data are given for the dissociation of (NH4)2HPO4 and anhydrous (NH4)3PO4. The study of the dissociation of the latter proves the existence of a compound (NH4)5H(PO4)2. RENE PERROTTE: Ricinic acid and 12-ketostearic acid. M. TIFFENEATJ and MLLE. B. TCHOUBAB: Transpositions in the cyclohexane series. The migratory aptitude of the migrating radical is influenced by its position in space. EDMOND URION: The oxidation of A-1-methylcyclohexene by selenious acid. GEORGES DUPONT and WITOLD ZACHAREWICZ: The cis and trans isomers of myrtanol. GEORGES MIGNONAC and ERWIN DITZ: The polymerisation of acetylene under the influence of heat. A yellow gaseous hydrocarbon, chlorene. The acetylene is passed in a rapid stream through a quartz tube at 750° C. and the products immediately cooled to +70° C. Two dimers of acetylene possessing the composition C4H4 were isolated, one of which possesses the remarkable property of being greenish yellow in the gaseous state: the name of chlorene has been given to it. JEAN HERBERT: Study of the corrosion figures of glass. The corrosion figures of glass change with the mode of attack, and have nothing in common with the figures formed when crystals are attacked by an appropriate reagent. The figures change with the concentration of the hydrofluoric acid used. G. DENIZOT: The structure of the Canary Islands considered in relation with the problem of Atlantis. The submersion of the Atlantic area was complete about the middle of the Tertiary period. Afterwards, the accumulation of volcanic products caused emergence from the sea at some points, and at times, relations with the African continent were possible. ANTONIN LANQUINE: Breaches of the Provengal chains at the borders of the northern and eastern Varois regions. R. FAIL-LETTAZ and R. BUREAU: The records of atmospherics at Tamanrasset (Hoggar) in the course of the Polar Year. F. RATHERY and P. M. DE TRAVERSE: Per-fusion of the intestine, and glycolysis. GEORGES BOURGUIGNON: Extemporaneous variations of the chronaxy under the influence of the pain caused by chronic rheumatism. ML ADEN PAIC: The rotatory dispersion of the sera of normal and syphilitic rabbits. The suggestion by Rondoni, that the rotatory power of the serum was of value in the diagnosis of syphilis could not be confirmed. MAURICE LEMOIGNE and ROBERT DESVEAUX: The origin of the nitrogen deficit in aerobic microbial cultures. The nitrogen deficiency is due to a transformation, probably an oxidation, of the ammonia arising from the decomposition of the proteins of the medium. HARRY PLOTZ: The filtrability of the tubercle bacillus. Utilising the method of electrophoresis, experiments are described proving that the tubercle bacillus can pass through the L2 Chamberland filter. This, in the author's opinion, is the true origin of what has been called the tuberculous ultra-virus. CHARLES SANNIE and JEAN VERNE: Study of the toxic action of cations on the cells of various organs cultivated in vitro.

Occurrence of Prosopistoma in Ceylon

THE recent discovery in Java by M. A. Lieftinck1 of larvae of a species of Prosopistoma (Insecta, Ephemeroptera), which he has named P. wouter, makes it desirable to direct the attention of zoologists to the existence of this interesting genus in Ceylon. In September, 1928, a single larva was captured by me in a rapid stream at Ougaldowa Estate, Belihuloya, Ceylon, about 5,000 ft., and briefly recorded in the administration report of the Colombo Museum for that year. It was found clinging to a stone in the manner described for the European species, P. foliaceum, Fourc.

VI. Trichoptera.

Six specimens of caddis-flies as well as caddis cases* are present in the collection of Latah fossils. Considering their aquatic development, it is not surprising that these insects should be represented, but the number of species is much larger than one would expect in a collection of this size. Fifteen per cent of all the specimens belong here. The magnitude of this proportion takes on some significance when we compare the trichopterous fauna of the Latah beds with that of the Florissant Shales, Scudder's examination of about twenty thousand Florissant insects showed that less than 4% of the species were Trichoptera, which means that the caddis-flies seem to he about four times as numerous at the Latah beds as at those of Florissant. It is also interesting to note that of the six Latah specimens, five are Limnephilids (representing five species) and the other is a Phryganea. In marked contrast to this, the specimens in the Florissant Shales comprise 95% Hydropsychids, 4% Phryganeids, and 1% Limnephilids. In other words, the family Hydropsychidæ, which is far and away the most abundant at Florissant, is absent in the Latah collection, while the family Limnephilidæ, of which only two species have been found in some twenty thousand Florissant insects, is represented by five species out of a total of 41 fossils from the Washington deposit. It must be admitted, of course, that these statements lose some of their force in view of the small number of Latah insects known, but I nevertheless believe that they have considerable significance. The Hydropsychidæ, which are so abundant at Florissant, breed only in rapid streams or active waters of lakes. The Phryganeidæ and very nearly all the Limnephilidæ, on the other hand, develop in standing water which usually contains much plant life, or in quiet streams. This would seem to verify Knowlton's conclusion, quoted above, that the lake which deposited the beds was shallow and contained a diverse flora.

SOME PARASITES OF SIMULIUM LARVÆ AND THEIR EFFECTS ON THE DEVELOPMENT OF THE HOST

Simulium larvæ, which are found in vast numbers in small rapid streams around Boston, are seen to feed by standing perpendicularly on rocks to which they are attached by a strong anal adhesive disc, and kept in position by silken threads secreted by the salivary glands. While thus anchored they spread out a pair of cephalic fans which act as strainers and collect small particles of food from the water. The head capsule is moulted independently of the body cuticle and exposes a new capsule which is at first white with a few dark spots on the vertex, but which rapidly becomes uniformly darkened all over. The thorax bears unusually well defined and large histoblasts of the imaginal wings, halteres and legs, and also on either side a histoblast of the pupal respiratory filaments, which by turning black when the larva is mature becomes very conspicuous at this stage of growth. The larvæ are infested by two parasites, namely a Mermis and a Sporozoön, both of which live in the body cavity.The Mermis does not affect the larval development to any extent, except by slightly increasing its size, but it inhibits the development of the histoblasts to such an extent that pupation becomes impossible.The embryo worms are probably caught by the cephalic fans of the larvæ and pass into the alimentary tract, through the walls of which they bore and live in the body cavity of the host till the latter matures. They then rupture the abdominal cuticle and pass into the water where they live a free life under stones in the bed of the stream. The number of worms contained by a single larva is usually only one, but as many as twelve have been found. A single worm measures 3 cm., which is about three times the length of the host. In some streams 25 per cent. of the larvæ were infested with this parasite. Parasitized larvæ never pupate, but are killed by the worms when they escape.The retardation in the development of the histoblasts is the opposite condition to that met with in prothetely which is usually caused by keeping larvæ at an abnormally high temeprature. This probably results in an increased supply of the enzymes which cause these histoblasts to develop. The Mermis apparently excretes some substance which lessens the supply or action of these enzymes and leads to metathetely.The Sporozoön parasite occurs in several forms in different localities. All these forms, however, live in the same way and appear to be related to the pébrine disease of Lepidoptera. The body, especially near the apex of the abdomen, becomes much distorted and swollen on account of its interior being closely packed with a white wooly material which on dissection is seen to consist of countless "spores" of minute size. Such parasitized larvæ are usually rather smaller than healthy individuals, but the histoblasts do not appear to be much affected. The parasite apparently enters the body cavity in the same manner as that described in the case of Mermis. Evidence of this is seen in a hypertrophied condition of parts of the mesenteric wall. From here it seems to pass to one or both of the sexual organs which are destroyed and become the nuclei for the great mass of spores which eventually fills the abdomen. The parasitized larvæ in this case also were never observed to pupate but died when mature. The spores are liberated by a rupture of the abdominal wall soon after the death of the host and pass into the water, after which stage they have not been seen. Up to 80 per cent. of the larvæ in some streams were found to contain large masses of this parasite but no cases of slightly parasitized larvæ were observed. There has been no second brood of Simulium larvæ this year, so it would seem that if the parasite is to appear next year there must be a secondary host in which the summer is passed.

An Alga Growing on Fish

IN NATURE of April 18, 1907, vol. lxxv., p. 599, it is noticed that Mr. A. D. Hardy found a cholorophyte, Myxonema tenue, ordinarily an inhabitant of rapid streams, also growing luxuriantly on some goldfish in a small pond, thus obtaining water friction necessary to its own well-being.

Progressive Waves in Rivers

THE stationary waves produced by the interaction of a rapid stream with its bed have been the subject of several investigations. The author finds that by a special mode of vision described in the paper the simultaneous presence of waves progressing down-stream can be readily detected.

A new pattern of thermostat designed to supply a rapid stream of water heated to a constant temperature

A new pattern of thermostat designed to supply a rapid stream of water heated to a constant temperature

OPHIOGOMPHUS

This genus of dragon flies is one of the groups whose members are accounted rare in collections, though quite abundant in nature. With the exception of three species, two of which have only been obtained in numbers by breeding, few imagoes have been taken. Although I have collected carefully for several years in localities where a few species were common enough, I have seen but three imagoes at large, but I have bred one species by hundreds, and have seen the exuviæ upon the banks of streams by tens of thousands.Nymphs of this genus seem to prefer the sandy or gravelly beds of clear, rapid streams, flowing through rocky woods. What becomes of the countless imagoes which issue from such places by night in early summer I have not as yet been able to find out.

II.—Observations on the Rounding of Pebbles by Alpine Rivers, with a Note on their Bearing upon the Origin of the Bunter Conglomerate

When preparing my address to Section C in 1886, I had much need of information as to the amount of rounding which takes place in rock fragments when transported by rapid streams. Useful information and references are given in Dr. A. Geikie's Text Book and in De Lapparent's “Traité de Géologie,” and there are the experimental researches of Daubrée in his “Géologie Experimental”; but from neither these nor other sources (so far as known to me) could I obtain what I wanted. I must, however, admit that I am less familiar with the talus heap of geological literature than I should be, and prefer making observations in the open air, to hunting for records of them in a library. So, as I had some opportunities of doing the former during my journey last summer, I record the results in the hope that they may be useful to others; first heartily thanking my companion, the Rev. E. Hill, for constant co-operation and assistance.

7. On the Periodic Variation of Temperature in Tidal Basins

The periodic variations of the temperature of water have been studied for some months at the Scottish Marine Station at Granton. The only tidal basin which has been considered as yet is the haven formed by the irruption of the sea into Granton Quarry. It has an area of about 7 acres; the tidal entrance is on the west side, and is so situated that no water can enter until about half tide; then it comes in as a very rapid stream for about three-quarters of an hour, when the rate falls off, and near high water it is the same as that of the rising tide on the shore. The ebb is gradual until the tide has narrowed the channel by uncovering the sandbanks which lie on each side of the entrance, then it is rapid for about an hour and a half, after which the water runs out ext'remely slowly, and does not absolutely cease until the tide begins to re-enter; but for from four to five hours the water-level inside is practically unaltered. The depth of the quarry at low water varies from 5 to 8 fathoms in the parts where observations were made, and at high water the depth is slightly more than 1 fathom greater. The bottom shelves off abruptly from the bar at the entrance.

PSEPHENUS LECONTEI—ON THE EXTERNAL ANATOMY OF THE LARVA

This singularly interesting larva occurs in abundance in the rapids of the Niagara above the Falls. The writer has taken it in other rapid streams in Western New York, also at different places in Michigan; besides, its occurrence in widely separated localities has been recorded by observers, hence we are led to believe that it is distributed throughout Eastern North America. Dr. Leconte has described another species, Ps. haldemanni, from the peninsula of California; its larva, it seems, has not been described.The first notice of our larva is that by Dr. Kay in Part VI. (Crustacea), page 53, Zoology of New York, 1844. It is described in that work as a new genus and species of Crustacea, under the name Fluvicola Herricki; a poor figure is given.

Strange Method of Crossing a Torrent

REFERRING to the inquiry of your correspondent as to the existence in modern times of the practice of carrying a stone to steady oneself whilst crossing a torrent, I may state that it is well known to the inhabitants of mountainous districts, and though practically it may not often have to be resorted to in Switzerland, where the streams are mostly well bridged, I have myself been glad to adopt it in Dauphine. As, however, a weight on the head or shoulders would, by raising the centre of gravity, rather diminish than add to the steadiness of the bearer, it is more usual to fill the lower side pockets of the coat, and perhaps take a large stone in each hand, and I have certainly found this useful in traversing rapid glacier streams when mid-thigh deep.