Papers by Trevor Ogden
Simple trigonometry is used to calculate the distance B (in degrees of latitude from the observer... more Simple trigonometry is used to calculate the distance B (in degrees of latitude from the observer) of a Noctilucent Cloud, if the height of the cloud is h and the angle of the cloud above the horizontal is C (degrees).
h = 2 r sin (B/2) . sin (B/2 + C) / cos (B + C)
where r is the radius of the Earth. The results are presented in graphical form, so that the distance can be read off from the angle of elevation for values of h of 70, 80 and 90 km.
Exposure, 2020
In the 1970s, Steve Beckett demonstrated that without careful quality control, measurements of as... more In the 1970s, Steve Beckett demonstrated that without careful quality control, measurements of asbestos in air were subject to huge errors. He co-designed an eyepiece graticule which helped make the measurements more accurate, and this continues to be used world-wide. He then changed career and became a expert of chocolate technology, and the editor of a book on the subject which is similarly world-famous. Steve died in January 2020, and this note summarises his contribution to occupational hygiene.
Books by Trevor Ogden
This is an English version of the memoirs of Ruth Klug, 1914-2009, (née Beling). They are especi... more This is an English version of the memoirs of Ruth Klug, 1914-2009, (née Beling). They are especially interesting as an account of the life of a prosperous family in Berlin before World War 2. Ruth was born into a manufacturing family, and brought up in Grunewald, a suburb of Berlin, and knew many of the leading members of Berlin society at that time, some of whom later became known for opposition to the Nazis. Her family were largely cushioned against the hardships of the 1920s, but because her father's family were Jewish Ruth was classified as a "Mischling" and suffered restrictions when the Nazi's came to power. In 1940 she married Ulrich Klug, a lawyer. Ulrich spent the war on the Eastern Front, but in 1945 managed to surrender to the Americans. After the war he became internationally-known as a jurist. He was Minister of Justice in the Hamburg government at the time of the Red Army Brigade terrorism, and the family was bombed and shot at, but survived.
Historical by Trevor Ogden
Dereham Heritage Trust Newsletter, 2021
From the Iron Age until at least the Middle Ages there were quite a few iron smelters in Norfolk,... more From the Iron Age until at least the Middle Ages there were quite a few iron smelters in Norfolk, and there were exports of nails in the 16th century. Where did the iron ore come from?
There was a concentration of iron-smelting sites along the Greensand outcrops in the West of the County, and another concentration in the North near the Cromer Ridge. The western smelters seem to have used the ironstone layers in the sand, and the Northern ones used the ironstone nodules found a metre or so down in parts of the Cromer Ridge, where there is plenty of evidence of mining. Ferric oxide in the sand of the ridge may have been solubilized and then deposited as nodules as the ground water permeated to a more alkaline layer. The limited data on the concentrations are consistent with this.
Dereham Heritage Trust Newsletter, 2024
The Cut Off Channel is a remarkable piece of engineering, protecting the Fens in Eastern England ... more The Cut Off Channel is a remarkable piece of engineering, protecting the Fens in Eastern England from flooding, by capturing excess flow in the waters draining Norfolk, and providing a water-supply reservoir for heavily populated and drier areas further south. The article focuses particularly on the River Wissey.
Dereham Heritage Trust Newsletter, 2022
Francis Wollaston, in the vicarage of East Dereham, Norfolk, was one of many amateur and professi... more Francis Wollaston, in the vicarage of East Dereham, Norfolk, was one of many amateur and professional astronomers who observed the 1769 Transit of Venus. This article sets his work in the context of everything else going on internationally to study this event, and how it relates to the other scientific interests of Francis' family.
Occupational Hygiene by Trevor Ogden
This tells the story of attempts to stop the work environment damaging health, from stone dust, l... more This tells the story of attempts to stop the work environment damaging health, from stone dust, lead, textiles, and many other hazards, through the industrial revolution and up to the 21st century. For much of this time, occupational hygiene was one social concern amongst others, such as child labour, bad housing, and exploitation of women. From about 1900, exposure measurements became possible, and with them the first limits. Improvement always had to work a way through financial and political interests. In the second half of the 20th century, the British Occupational Hygiene Society provided a focus for better ideas and a more organised and better-trained profession.
In the 1920s, EL Middleton of the British Factories Inspectorate took hundreds of breathing-zone ... more In the 1920s, EL Middleton of the British Factories Inspectorate took hundreds of breathing-zone samples of silica in a wide range of industries, using an Owens Jet impactor, and counting and sizing the particles by oil-immersion microscopy, attempting to take account of the finding that only the finest particles are retained in the lung. For each sample he reported the total number concentration, and the percentage of particles with a maximum dimension > 2μm. Consideration of what is known of the shape and aerodynamic behaviour of quartz particles in particular, and fitting lognormal distributions to Middleton's counts, leads to the following formula.
G = (0.146 P + 0..47) mg/m3
where G is the respirable mass concentration by the definition in European Standard EN 481, N is the count obtained by Middleton in particles/cm3 , and P is the percentage of those particles with maximum dimension > 2 μm. There are major sources of uncertainty in this formula, the most important being the efficiency of the sampler: there are contradictory reports in the literature about this, and the sampler design may have been changed during its history. These problems mean that the formula may give results in error by a factor or two or three. Also, it must be born in mind that the sampling method gave only spot samples, not shift average exposures.
The results of asbestos slide exchanges are analysed to derive the relationship of precision with... more The results of asbestos slide exchanges are analysed to derive the relationship of precision with the number of fibres counted, and to propose a protocol for quality assurance.
Exposure, 2017
This article highlights main points of the 2017 revision of European Standard EN689, on testing c... more This article highlights main points of the 2017 revision of European Standard EN689, on testing compliance with exposure limits for airborne substances, with special attention to the tests in the standard.
The Microscope, 1986
Euparal has been used as a mountant for microscopy since 1906, and in the 1980s came into use for... more Euparal has been used as a mountant for microscopy since 1906, and in the 1980s came into use for mounting membrane filters in asbestos measurement. The history of its manufacture is traced. The refractive index of mounts with the original formulation has been stable for over 40 years.
The Microscope, 1986
The permanence of various clearing methods for membrane filters bearing asbestos fibres was teste... more The permanence of various clearing methods for membrane filters bearing asbestos fibres was tested by repeat photomicrography of the same field for more than 5 years. Filters cleared with DMF and mounted with Euparal showed no change, but other clearing methods, including acetone vapour, led to changes of different degrees.
Inhaled Particles IV, 1977
This 1977 paper was the first to propose in detail that a definition for “total” airborne particu... more This 1977 paper was the first to propose in detail that a definition for “total” airborne particulate should be based on what was inhaled. It presented measurements of what this meant for particles between 5 and 30 μm aerodynamic diameter, nose or mouth breathing, at inhalation rates up to 80 l/min, at various angles to winds of 0.75 m/sec and 2.75 m/sec. The effects of averaging for all wind directions, halving the area of the mouth and nose orifices, or of tilting the model forward, were examined. However, the inhalation flow was steady, so the effect of cyclical breathing was reconstructed. A later paper by the same team added similar measurements in calm air (Ann Occ Hyg, 21:41-50 (1978)). Other workers greatly widened the range of variables studied, and the directionally-averaged inhalation efficiency became the basis of the “inhalable” definition in European and International Standards. The paper was presented at the 1975 Inhaled Particles symposium, and published in Inhaled Particles IV (Pergamon, 1977), but up to now has not been available on-line.
Journal of Occupational and Environmental Hygiene, 2012
The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.
Names studies by Trevor Ogden
There are 13 surnames in the 1881 census which occurred more frequently in Norfolk than any other... more There are 13 surnames in the 1881 census which occurred more frequently in Norfolk than any other county, and whose origins are believed to be Old Norse (ON) personal names. These surnames appear to be commoner in the parts of the county where ON place-names are more frequent; such place-names are usually taken as an indicator of Viking settlement. The apparent relationship was investigated by grouping the census enumeration districts into three classes according to the number of ON place-names that the enumeration districts included. It was found that a person living in a part of Norfolk in 1881 with many ON place-names was about 4.5 times as likely to have an ON-derived surname as a person living in an area with few, and a person in an area with an intermediate number was 2.7 times as likely. Yarmouth and Norwich were treated separately, and come between the most frequent and intermediate classes. At first sight the strength of this association is surprising, but Scandinavian given names are known to have continued in use to the time when many families had hereditary surnames. It is therefore not surprising that such names were created, and there are many other examples of surnames remaining concentrated until modern times in the areas in which they were formed
Ogden and McClure (2021) divided Norfolk into zones according to the density of Old Norse (ON) pl... more Ogden and McClure (2021) divided Norfolk into zones according to the density of Old Norse (ON) place-names. This density is often taken as a marker of Scandinavian settlement. They showed that in the 1881 census the number of holders of surnames derived from ON personal names was about 4.5 times as great in the zone with many ON place-names as in the zone with few, with the rest of Norfolk having an intermediate number. This paper considers the dispersal of surnames by extinction and migration, and compares the dispersal of the ON-derived surnames with that of locative names from the same parts of Norfolk. This does not undermine the analysis of Ogden and McClure.
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Papers by Trevor Ogden
h = 2 r sin (B/2) . sin (B/2 + C) / cos (B + C)
where r is the radius of the Earth. The results are presented in graphical form, so that the distance can be read off from the angle of elevation for values of h of 70, 80 and 90 km.
Books by Trevor Ogden
Historical by Trevor Ogden
There was a concentration of iron-smelting sites along the Greensand outcrops in the West of the County, and another concentration in the North near the Cromer Ridge. The western smelters seem to have used the ironstone layers in the sand, and the Northern ones used the ironstone nodules found a metre or so down in parts of the Cromer Ridge, where there is plenty of evidence of mining. Ferric oxide in the sand of the ridge may have been solubilized and then deposited as nodules as the ground water permeated to a more alkaline layer. The limited data on the concentrations are consistent with this.
Occupational Hygiene by Trevor Ogden
G = (0.146 P + 0..47) mg/m3
where G is the respirable mass concentration by the definition in European Standard EN 481, N is the count obtained by Middleton in particles/cm3 , and P is the percentage of those particles with maximum dimension > 2 μm. There are major sources of uncertainty in this formula, the most important being the efficiency of the sampler: there are contradictory reports in the literature about this, and the sampler design may have been changed during its history. These problems mean that the formula may give results in error by a factor or two or three. Also, it must be born in mind that the sampling method gave only spot samples, not shift average exposures.
Names studies by Trevor Ogden
h = 2 r sin (B/2) . sin (B/2 + C) / cos (B + C)
where r is the radius of the Earth. The results are presented in graphical form, so that the distance can be read off from the angle of elevation for values of h of 70, 80 and 90 km.
There was a concentration of iron-smelting sites along the Greensand outcrops in the West of the County, and another concentration in the North near the Cromer Ridge. The western smelters seem to have used the ironstone layers in the sand, and the Northern ones used the ironstone nodules found a metre or so down in parts of the Cromer Ridge, where there is plenty of evidence of mining. Ferric oxide in the sand of the ridge may have been solubilized and then deposited as nodules as the ground water permeated to a more alkaline layer. The limited data on the concentrations are consistent with this.
G = (0.146 P + 0..47) mg/m3
where G is the respirable mass concentration by the definition in European Standard EN 481, N is the count obtained by Middleton in particles/cm3 , and P is the percentage of those particles with maximum dimension > 2 μm. There are major sources of uncertainty in this formula, the most important being the efficiency of the sampler: there are contradictory reports in the literature about this, and the sampler design may have been changed during its history. These problems mean that the formula may give results in error by a factor or two or three. Also, it must be born in mind that the sampling method gave only spot samples, not shift average exposures.