scholarly journals I. On the laws of the tides on the coasts of Ireland, as inferred from an extensive series of observations made in connection with the ordnance survey of Ireland

1845 ◽  
Vol 135 ◽  
pp. 1-124 ◽  
Keyword(s):  
Accurate Determination ◽  
High Water ◽  
Eastern Coast ◽  
Western Coast ◽  
Ordnance Survey ◽  
The North ◽  
Small Depth ◽  
Open Sea ◽  
The Difference ◽  
Hydrostatic Level

In the spring of 1842 I was informed by Colonel Colby, R. E., Director of the Trigonometrical Survey, that in the operations of the Survey of Ireland it had become necessary to adopt a line of reference for the elevations ascertained in the running of various lines of level through the country; and that it was his intention to institute a series of observations of the height of the water in different states of the tide, in order to refer the levels to the mean height of the sea, or to its height at some definite phase of the tide. Colonel Colby stated also that he was desirous that the observa­tions should be made subservient to improvements in the theory of the tides, and requested my assistance in sketching a plan of observation which would be most likely to contribute to that end. In reply, I made the following suggestions:—That great care should be taken in the accurate determination of time at every station, and that for this purpose the non­commissioned officer of the Royal Sappers and Miners who had the care of the observations at each station, should be entrusted with a pocket chronometer, and that an officer should, at least twice during the series of observations, visit every station, carrying, for comparison, an itinerant chronometer whose error on Greenwich time was accurately known from astronomical observations. That stations should be chosen on the eastern as well as on the western coast, in order to determine the difference of level, if any, between an open sea and a partially inclosed sea. That on the north-eastern coast, stations should be selected at smaller intermediate distances than at other parts of the coast, with the purpose of removing, if possible, the doubt which appears to exist as to the progress of the semidiurnal tide-wave through the North Channel. That, where practicable, several stations should be selected on each of the large rivers or estuaries, in order to ascertain the nature of the modification which the tide-wave undergoes in passing up a contracted channel of comparatively small depth. That the series of observations should be so arranged, that, at every station, one complete tide (from high water to high water, or from low water to low water) should be completely observed on every day, its observations being made at small equidistant intervals. That supplementary observations, applying only to the neighbourhood of the low water or high water omitted in the observations of the complete tide, should also be made, for the development of the principal facts of diurnal tide. Finally, that the zeros of the tide-gauges should be connected with the principal lines of level, so that every observation should be referred to the same hydrostatic level.

XXV. Note on the tides in the port of London

1832 ◽  
Vol 122 ◽  
pp. 595-599 ◽  
Keyword(s):  
Great Britain ◽  
A Priori ◽  
High Water ◽  
Eastern Coast ◽  
The Moon ◽  
Cape Of Good Hope ◽  
The Difference

Mr. Stratford has favoured me with a comparison of the predicted times of high water deduced from Mr. Bulpit’s Tables, White’s Ephemeris, and the British Almanac, with the observations at the London Docks. These observations are, unfortunately, so imperfect, that the differences must not be entirely attributed to the errors of the Tables, which, however, seem susceptible of much improvement. I subjoin this comparison; and in order to convey an idea of the confidence which may be placed in the observations, I also subjoin a comparison, by Mr. Deacon, of the observations at the London and St. Katherine’s Docks, which are made according to the same plan, and of which the merit is the same. The differences in the determinations at these two places, which are only about a quarter of a mile distant from each other, may serve to indicate the reliance which can be placed in either. In my paper on the Tides at Brest, I remarked that the retard or the constant λ — λ, is considerably greater as deduced from observation here than at Brest. That this must be the case is also evident from the following very simple à priori considerations.—The highest high water takes place when the moon passes the meridian at a time equal to the retard. The tide is propagated from Brest to London, round Scotland, in about twenty-two hours, that is, supposing the tide which takes place in our river to be principally due to that branch of the tide which descends along the eastern coast of Great Britain, which I believe to be the case. The highest tide therefore is propagated from Brest to London in about twenty-two hours, and the difference in the retard or in the constant λ — λ, will be nearly the moon’s motion in twenty-two hours, or about 11°; I made the difference in the retard from observation 10°. The tide takes about fifteen hours to reach Brest from the Cape of Good Hope; no doubt the retard there is considerably less.

scholarly journals XI. Researches on the tides.—tenth series. on the laws of low water at the port of plymouth, and on the permanency of mean water

1839 ◽  
Vol 129 ◽  
pp. 151-161 ◽  
Keyword(s):  
High Water ◽  
Level Line ◽  
English Channel ◽  
Know How ◽  
North Shore ◽  
The North ◽  
South Shore ◽  
The Subject ◽  
The Mean ◽  
The Difference

In former communications to the Society, the laws of high water at Plymouth and other places have been the subject of my researches. These being obtained, the laws of low water are a subject of importance and interest on many accounts. The first ground of my pursuing this subject was the desire to ascertain how far the mean water , that is, the height midway between high and low water, is permanent during the changes which high and low water undergo. That it is approximately so at Ply­mouth, had been ascertained both by Mr. Walker and myself, by means of a com­parison of a short series of observations. But it was desirable to know with more exactness what was the real amount of this permanency, when, by using a long series of observations of high and low water, the irregularities arising from accident, and from taking imperfect cycles of inequalities, were eliminated. There was another reason which made this inquiry important at the present time. An operation has been recently carried on by the direction and at the expense of the British Association, with a view of ascertaining what surface ought to be taken as the permanent level of the sea. A Level Line has been carried with great care and accuracy from the north shore of Somerset to the south shore of Devon ; and the po­sition of this line has been fixed, so as to be recognised at any future time, by means of marks at Axmouth, at East Quantockshead, at Stolford, and at Portishead. This line has also been referred to the sea at its extremities ; and the observations show that the height of mean water coincides, at least very nearly, at different places, as well as at the same place at different times. While the difference of levels of low water at Axmouth on the English Channel, and Wick Rocks on the Bristol Channel, is not less than twelve feet; the mean water at those two places coincides in level within a few inches. In order to determine further what accuracy may be attained in this result, we are led to inquire what is the degree of permanency at one place. I may further add, that it cannot but be instructive to know how far the corrections of the height and time of low water, for lunar parallax and declination, agree in form and amount with the same corrections already obtained for high water.

scholarly journals Stability Assessment and Geomorphological Evolution of Sea Natural Arches by Geophysical Measurement: The Case Study of Wied Il-Mielah Window (Gozo, Malta)

2021 ◽  
Vol 13 (22) ◽  
pp. 12538
Author(s):  
Giovanni Leucci ◽  
Raffaele Persico ◽  
Lara De Giorgi ◽  
Maurizio Lazzari ◽  
Emanuele Colica ◽  
...  
Keyword(s):  
Methodological Approach ◽  
Western Coast ◽  
The North ◽  
Open Sea ◽  
Passive Seismic ◽  
Geophysical Measurement ◽  
Natural Monument ◽  
The Stability ◽  
Geomorphological Evolution ◽  
Ground Penetrating

The Wied il-Mielaħ Window (Gozo–Malta) is a limestone natural arch on the north-western coast of the island of Gozo in Malta. It is located at the end of the Wied il-Mielaħ valley north of the village of Għarb. This natural arch is less well known than the Azure Window, which collapsed in March 2017 following a heavy storm, but notwithstanding, it is an imposing and important natural monument too. In the past, the Wied il-Mielah valley was responsible for discharging wastewater from the surrounding localities to the Mediterranean directly at the Wied il-Mielah Window. The sewage flag was often clearly visible underneath the archway into the open sea. The natural features of the arch provide an outstanding touristic attraction. To avoid what happened to the Azure Window, a methodology for the evaluation of the collapse hazard, combining passive seismic, ground penetrating radar (GPR), geological/geomorphological surveys and mine engineering methods, is here proposed. In this study, a methodological approach was applied, based on the following: (i) passive seismic method to study the physical–mechanical characteristics of the rock mass that constitutes the window; (ii) GPR method in order to demonstrate the conservation state (i.e., the intensity of fracturing); (iii) geological/geomorphological surveys in order to obtain a crack pattern; and (iv) scaled span empirical analysis in order to evaluate the stability of the arch. The calculation of the safety factor, with a static method, gave a value equal to 3.75 with a probability of collapse of the marine arch within 50 and 100 years.

Soil-vegetation interactions in coastal landscapes - erosion reduction as ecosystem service in the context of integrated coastal zone management

2021 ◽  
Author(s):  
Viktoria Kosmalla ◽  
Jan-Michael Schönebeck ◽  
Björn Mehrtens ◽  
Kara Keimer ◽  
Maike Paul ◽  
...  
Keyword(s):  
Ecosystem Services ◽  
Real World ◽  
Coastal Ecosystems ◽  
Eastern Coast ◽  
Coastal Protection ◽  
Western Coast ◽  
Climate Change Scenarios ◽  
Dune System ◽  
The North ◽  
Joint Research Project

<p>The joint-research project "Gute Küste Niedersachsen" is a multidisciplinary approach across spatial and temporal scales investigating ecosystem services for coastal protection. Current national coastal protection concepts predominantly target flood protection and rarely consider additional benefits to coastal ecosystems or vice versa. How maritime landscapes, such as salt marshes, coastal white dunes or a diversification of dike vegetation, can be integrated into approaches of coastal protection without compromising protection levels is the driving question in "Gute Küste Niedersachsen" and heeds recent European Framework directives calls for the restoration of a good ecological status. An in-depth understanding of dynamics within coastal ecosystems, covering eco-hydrodynamics and eco-geomorphodynamics is developed in real world laboratories at the German North Sea coast, as part of the project.<br>Systematic field observations in collaboration between biologists, geo-ecologists and coastal engineers are conducted to identify seasonal changes of vegetation regarding zonation, height, root length density and bio-mechanical parameters like bending stiffness or tensile strength. The differences of bio-mechanical vegetation traits from specific plant species, e.g. the European beach grass <em>Ammophila arenaria</em>, will indicate differences in bio-stabilization states.<br>Complementary field data of topography and soil parameters, e.g. shear and pull-out resistance, among other parameters, are acquired, employing specifically developed instrumentation like the DiCoastar for automatic and digital measurements of shear resistance over rotation angle. Additionally, values such as water and biomass content obtained from soil samples help to elucidate erosion stability of coastal ecosystems.<br>Field campaigns are focused on two real world laboratories, the tidal barrier island of Spiekeroog, Germany, and a coastal mainland section. Spiekeroog offers a variety of dune systems exposed to divergent environmental conditions such as established and recently developing natural dunes at the north-eastern coast, dunes that are used for coastal protection at the north-western coast, dunes in combination with a sea wall that are already supported by sand nourishment at the western coast or established dunes along the south-western tip of the island. Furthermore, the island holds a unique setting with an engineered dune, which was created to integrate a dike system into the landscape. This offers a one-of-a-kind opportunity to investigate differences between six different dune system types within close proximity regarding their vegetation bound bio-mechanical properties and linked soil-bound erosion resistance.<br>In addition, Spiekeroog offers an abandoned dike line, for which a sectional re-planting is rolled out with alternative seed combinations for ecologically upgrading grass dikes and boost plant diversity while coastal protection is maintained. A direct comparison against a sea dike is made at the second real world laboratory situated at the adjacent mainland coast. This setting facilitates the comparison between different biological revetment types and their respective performance in coastal protection regarding wave-soil-vegetation interactions.<br>In a subsequent step, the extensive data set will be used to develop surrogate plant models and mimic nature in hydraulic laboratories and numerical simulations to project system performance under climate change scenarios. Finally, technical guidance as well as policy recommendations will be derived for enhancing ecosystem services of artificial structures for coastal protection.</p>

The propagation of tide and surge in an estuary

1955 ◽  
Vol 231 (1184) ◽  
pp. 8-24 ◽  
Keyword(s):  
Shallow Water ◽  
Theoretical Investigation ◽  
High Water ◽  
Meteorological Conditions ◽  
Order Of Approximation ◽  
Progressive Wave ◽  
Thames Estuary ◽  
Small Depth ◽  
Open Sea ◽  
Progressive Waves

This paper is a theoretical investigation of the distribution, along an estuary, of a combination of tide and surge which have been generated in the open sea. The following results relate to the same sequence of meteorological conditions over the sea. For a single progressive wave, the height of a surge whose maximum occurs near to the time of tidal high water is less than that of a surge whose maximum occurs near to the tune of tidal low water, and it decreases as the range of tide increases. To the order of approximation followed in the paper, these differences are due to friction and increase with distance from the sea. For a standing oscillation, the following results relate to the head of the estuary. When the primary surge rises to its maximum more rapidly than it falls from it, and when this maximum occurs near to the time of tidal high water, the effect of shallow water is to make the surge increase as the range of tide increases, and the effect of friction is to make the surge decrease as the range of tide increases. On applying the formulae of the paper relating to progressive waves to the Thames Estuary, it appears that, owing to the small depth of water at mean level, the details only hold for a few miles from the sea. But the tendencies enumerated should hold all the way to London.

scholarly journals Reconstructing the lost contours of Charles Hutton

2019 ◽  
Vol 1 ◽  
pp. 1-2
Author(s):  
Karen Rann ◽  
David Fairbairn ◽  
Ella Southern
Keyword(s):  
18Th Century ◽  
Accurate Determination ◽  
Digital Terrain Model ◽  
Considerable Degree ◽  
Field Observations ◽  
Contour Map ◽  
Ordnance Survey ◽  
The North ◽  
Land Surveying ◽  
Fixed Base

<p><strong>Abstract.</strong> This study reports on an historical investigation of map-making practice and achievement from the late 18th century, and attempts to reconstruct the practices and outcomes of an innovative surveying and mapping exercise, using historical data and contemporary geospatial data handling. The episode involves the processing of data captured as part of an extensive project by the then (British) Astronomer Royal, Maskelyne, in the mid 1770s, to measure the gravitational attraction and density of the earth.</p><p>This experiment was conducted on the isolated mountain of Schiehallion in Central Scotland, and resulted in several differing approaches to calculating the mass of the mountain, and determining and interpreting the resultant effect on gravity measurements on its slopes. In order to do this, an accurate determination of “the figure and dimensions of the hill” (Maskelyne, 1775) was required. The survey work was undertaken under Maskelyne’s supervision by his previous assistant, Barrow, and local surveyor, Menzies.</p><p>The data collected included astronomical observations to establish latitudinal positions, lengths of fixed base lines (one to the north of the mountain and one to the south), a standard traverse around the mountain to establish fixed points, and transects/vertical profiles radiating from those points. The land surveying techniques were known and widely used, although at the time having only been recently documented, in the book ‘A Treatise on Mensuration’. This was published in 1770 by Charles Hutton (1737-1823) a Newcastle-born mathematician, and was the first volume on surveying written in English. In 1773 Hutton had moved south to become Professor of Mathematics at the Royal Military Academy, Woolwich, and became known to the Royal Society which asked him to process Maskelyne’s data.</p><p>The original field observations (Figure 1), were published in Hutton’s extensive account of his work (Hutton, 1778), which also explained how he was to calculate the mass of the mountain, dividing the landscape into a set of vertical prisms collectively defining the mountain’s shape. Smallwood (2007) describes how Hutton’s volume calculations, along with rock, geology and gravity information, can help estimate earth density.</p><p>The prisms, arranged as circular sections (some individually coloured in Figure 2 to exemplify), had their heights calculated with reference to the height points within them. Clearly, however, some prisms had no heights associated with them. Hutton devised a method of interpolation of prism height for those which had no height data by creating a surface defined by contours: “I fell upon the following method … by which I was enabled to proceed in the estimation of the altitudes both with much expedition and a considerable degree of accuracy. This method was the connecting together by a faint line all the points which were of the same relative altitude: by so doing, I obtained great number of irregular polygons lying within and at some distance from, one another, and bearing a considerable degree of resemblance to each other: these polygons were the figures of so many level or horizontal sections of the hills, the relative altitudes of all the parts of them being known; and as every base or little space had several of them passing through it, I was thereby able to determine the altitude belonging to each space with much ease and accuracy.”</p><p>Although isolines were long established on some maps, and isobaths (depth curves), in particular, were visible on some hydrographic charts from the early 18th century, Hutton has some claim to be the first to use lines of equal altitude (contours) on land-based maps. Unfortunately, despite describing the method of using a ‘faint line’ to elucidate the contours, no graphical artefact exists: there is no evidence that Hutton, or anyone associated with the gravity project, ever published the contour map of Schiehallion.</p><p>Elsewhere in his account of the data processing (Hutton, 1778), significant doubts are expressed about the accuracy and validity of some of the observations, and there is the possibility that Hutton blocked publication of the contour map because of inaccurate observation or conflicting calculations.</p><p>However, the presentation of the full set of observations should allow for a reconstruction of the missing contour map. Processing and visualisation has already been undertaken manually by Johnson (Figure 3).</p><p>An attempt was also made to use standard land surveying software to handle the field observations to calculate and map the data. The Star*NET package (Microsurvey, 2018) has been applied to the traverse observations, using techniques of least squares to obtain the most precise positioning of the surrounding stations. The LSS package (McCarthy Taylor, 2018) is used to enter the tacheometric detailing observations, and create an accurate digital terrain model based on the observed data from over 240 years ago. The contour lines derived from this model will be compared with current survey data provided by the British Ordnance Survey, and with satellite derived digital elevation datasets. It is hoped that data manipulation can be undertaken to successfully create a contour map which Charles Hutton would have been happy to publish.</p>

XVII.—The Geology of Gigha

1927 ◽  
Vol 55 (2) ◽  
pp. 395-409
Author(s):  
W. J. McCallien
Keyword(s):  
Eastern Coast ◽  
Western Coast ◽  
Main Island ◽  
North East ◽  
The North ◽  
South West ◽  
Nearest Point ◽  
North Eastern ◽  
As If

Gigha is a little-visited island off the western coast of Kintyre and between the latter and the island of Islay. It lies about 5¼ miles south-west of West Loch Tarbert, and a little over 1½ miles from the nearest point of Kintyre where the mainland runs out for 1½ miles in the low, sandy, raised beach of Runahaorine (figs. 1 and 10).The island is 6 miles in length from north-east to south-west, and has a greatest breadth of 2 miles. All round it are innumerable smaller isles, all elongated in the same direction as Gigha. Of these the most important are Cara, 1 mile from north-east to south-west by ½ mile in breadth, and Gigalum, ½ mile by ⅕ mile, and Craro, which is smaller still (figs. 2 and 10). The island forming Ardminish Point, on the eastern coast of Gigha, and Eilean Garbh, at the north-eastern end, will be dealt with here as if they were part of the main island, since at low tide they are connected with it by sandy isthmuses.

Tidal Currents of the North Sea

1899 ◽  
Vol 22 ◽  
pp. 478-481
Author(s):  
Alexander Buchan
Keyword(s):  
North Sea ◽  
Tidal Flow ◽  
High Water ◽  
Eastern Coast ◽  
The South ◽  
Orkney Islands ◽  
The North ◽  
Deep Channel ◽  
Moray Firth ◽  
The North Sea

In the article “Tides” in the Encyclopœdia Britannica, Professor George Darwin, quoting Sir George B. Airy, remarks that the tides of the North Sea present a very remarkable peculiarity. Along the eastern coast of England as far as the mouth of the Thames, the tide-wave, coming from the Atlantic round the Orkney Islands, flows towards the south. Thus, on a certain day, it is high water in the Moray Firth at 11 a.m., at Berwick at 2 p.m., at Flamborough Head at 5 p.m., and so on to the entrance to the Thames. Thus, on the day supposed, it will be high water off the Thames at 11 p.m., the tide having travelled in twelve hours from the Moray Firth.It is further stated that the North Sea is considerably deeper on the English side than on the German side; so much so, that the tide-wave coming from the north runs into a deep bay of deep water, bounded on the west side by the Scottish and English coasts as far as Newcastle, and on the east side by the great Dogger Bank. As far as the latitude of Hull, the English side is still the deep one; and though a species of channel through the shoal there allows an opening to the east, yet immediately on the south of it is the Wells Bank, which again contracts the deep channel to the English side.It is not stated here that the deeper water of the North Sea close to the Scottish and English coasts determines the course of the southward tidal flow to be close to these coasts; but for that course taken, no other cause is suggested.

Allometric Relationships for Estimating Biomass in Multi-stemmed Mangrove Trees

1997 ◽  
Vol 45 (6) ◽  
pp. 1023 ◽  
Author(s):  
B. F. Clough ◽  
P. Dixon ◽  
O. Dalhaus
Keyword(s):  
Stem Diameter ◽  
Eastern Coast ◽  
Western Coast ◽  
Allometric Relationships ◽  
Above Ground Biomass ◽  
Rhizophora Stylosa ◽  
Ground Biomass ◽  
The North ◽  
Eastern Australia ◽  
North Eastern

A procedure is described for obtaining allometric relationships between stem diameter and above-ground biomass for multi-stemmed trees of the mangroves Rhizophora stylosa and Avicennia marina. The procedure treats each stem as discrete tree that shares a proportion of the butt and other elements common to all stems. Linear log–log relationships were obtained between stem diameter and the dry weights of each above-ground component. Allometric relationships between stem diameter and total above-ground biomass were similar to those for single-stemmed trees in north-eastern Australia, but multi-stemmed trees on the west coast had much greater proportion of their biomass in the form of prop roots than single-stemmed trees of comparable stem diameter on the north-eastern coast. This is attributed to the arid environment on the north-western coast of Australia.

scholarly journals Paläoklimatologische Eindrücke aus Neuseeland

1965 ◽  
Vol 16 (1) ◽  
pp. 226-238
Author(s):  
Martin Schwarzbach
Keyword(s):  
New Zealand ◽  
Windward Side ◽  
Western Coast ◽  
Volcanic Area ◽  
The North ◽  
Long Time ◽  
Glacier Ice ◽  
Climatic History ◽  
The Difference ◽  
Wet Climate

Abstract. Some observations and remarks about the climate and paleoclimate of New Zealand, founded on journeys and the work of New Zealandic geologists. Some peculiarities of the climate (fig. 1). New Zealand has a relatively cool and wet climate (similar to Tasmania at the present). There is a very conspicious difference between the very humid windward side and the arid lee-side of the Southern Alps (also in the vegetation, fig. 2). „Edaphically caused deserts" begin to develop in the volcanic area of the North Island (fig. 3). The glaciers on the western coast of New Zealand (fig. 4), especially Franz Josef and Fox Glaciers, are impressive examples for the coexistence of lush, nearly subtropical rainforests (with tree-ferns) with glacier ice (figs. 6, 8). Therefore they are especially important for paleoclimatologists and for the interpretation of climatic indicators. Both glaciers have their tongues near the sea, nearly 2000 mts. below snow-line. Their recession (fig. 7) was 1200 and 1800 m respectively in 21 years. The cause for the low position of the tongues is to bee seen in high precipitation in connexion with the altitude and steepness of the mountains. Climatic history of New Zealand. The Quaternary is not treated; it only is referred to the influence of recent tectonic movements on the terraces. — The climate of the Tertiary was temperate to subtropical and humid. Maximal temperatures did not occur (as in Europe and North America) in the older, but (as in Australia) in the middle Tertiary (fig. 9). The author tries to explain this difference by the combination of 2 curves (fig. 10): one is the curve of changing latitude, caused by drift, the other is the general trend of the decline of temperature in Tertiary time. Because Australia obviously moved towards the equator, but Europe (if at all) towards the pole, the resulting curve is different in both continents. — Also the Mesozoic climate was neither tropical nor arid. Perhaps the Permian was a little warmer than in Australia. Compared with Australia, the climatic history is distinctly different. Australia changed from a polar climate to a subtropical and tropical one since the Carboniferous-Permian period, but New Zealand seems to have remained more or less in the same climatic zone during this long time. We don't yet know whether the difference between New Zealand and Australia is only apparent (caused by gaps in our knowledge), or is caused by an independent northward drift of both regions (Australia quickly, New Zealand more slowly).

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