Meteorologist s profile John Dalton

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1 Meteorologist s profile John Dalton Howard and Sylvia Oliver Oxford ``60, 71, 30.18, SW 1, Little Rain. This weather report appeared posthumously in the Manchester Guardian in The temperatures inside and out, pressure, wind and precipitation at 2100 local time (LT) on 26 July 1844 are the last recorded words of the dedicated meteorological observer John Dalton (1766± 1844), pictured in Fig. 1. He died in his room before he could make the next morning s 0800 LT readings. What better epitaph could there be for someone who had studied meteorology all his working life and was credited with 206

2 Fig. 1 John Dalton holding a measuring beaker, from an etching by James Stephenson (reproduced by permission of the Manchester Literary and Philosophical Society) making over observations? Although he was better known for his early work in atomic theory and chemistry, his meteorological achievements are not insignificant. The Royal Meteorological Society previously marked the centenary of his death with a short article in the Quarterly Journal (Manley 1944). This profile coincides with the bicentenary of the publication of some of his key papers. Life and times John Dalton was born in the village of Eaglesfield a few miles from Cockermouth in Cumbria and his house, though altered, is still there marked with a plaque. His Quaker family was initially extremely poor but his father was able to teach him mathematics, and John attended the Friends school until he was 12 years old. Such was his progress that, when his teacher left, John took over the school himself. During this period he also obtained a thorough grounding in mathematics under the tuition of a gentleman who lived nearby. In 1781 John was asked to teach at a Quaker school in Kendal, jointly with his brother. After taking advice from the Council of Friends this was agreed. He walked to Kendal carrying one of the new umbrellas which had just become available in Cockermouth. When their cousin who ran the school left in 1785 the two brothers took over with the help of their sister, who came to keep house. Their advertisements proudly state that the school ``has a valuable library of books on history, mathematics and natural philosophy, also an air pump, globes and several other philosophical, mathematical and optical instruments. It was during his time at Kendal that Dalton began his life-long interest in things meteorological, stimulated by his contacts with the blind scientist John Gough who gave him the run of his library and with whom he had frequent scientific discussions. In 1793, following an invitation from Dr Thomas Barnes, Principal of the New College Manchester (now moved to Oxford University as Harris Manchester College), Dalton took up the position of tutor (he styled himself ``Professor of Mathematics and Natural Philosophy ) which he held until It was during his time there that he produced some of his most important meteorological work. After leaving the college Dalton continued to live simply in Manchester, spending his time teaching and researching on subjects within and far beyond natural philosophy. He presented papers to, and played an increasingly important role in, the Manchester Literary and Philosophical Society, with an extended period as its President. Public acclaim led to lecture tours around the UK and abroad and to the award of many honours, including an FRS, various degrees and eventually a Government pension. On his death the Manchester Corporation mounted a vast funeral with a milelong procession attended by mourners. As a person Dalton lived modestly and never lost his rustic accent and his simple Quaker approach to life. In addition to Quaker activities on Sundays, he allowed himself just one afternoon of relaxation each week to play bowls. He never married, his main excuse being ``I never had the time. He never really adapted to the social expectations of international fame and continued with basic tutoring throughout his life. The rigid pattern of his life and his meticulous approach to measurement and research made him an ideal meteorological observer. 207

3 Meteorological studies During his years at Kendal, Dalton refined the skill of making barometers and began taking regular meteorological observations. His thermometer was situated ``without, in a garden, under the shade of a rather large gooseberry tree facing north: the garden open to the countryside to the north and has houses at a distance of 8 or 10 yards [7 or 9 m] to the south. His observations were taken between 0600 and 0800 LT, 1200 and 1300 LT, and 2100 and 2200 LT. A friend, Peter Crossthwaite, took broadly similar measurements at Keswick. He used a whipcord hygrometer whose length was humidity dependent and a 10 in (250 mm) diameter raingauge ``sufficiently distant from trees, houses &c. Dalton s main meteorological achievements can be divided into five main areas, with work on hydrology and evaporation being published almost exactly 200 years ago. A textbook on meteorology After his time at Kendal Dalton published his book Meteorological observations and essays (Dalton 1793). This was primarily intended as a meteorological textbook and was in two sections. The first gave details of meteorological measurement techniques and listed monthly values for Kendal and Keswick, together with London data from the Royal Society, all with appropriate comments. Articles giving data on cloud heights, wind, duration of snow-cover and appearances of the aurora (then generally considered to be a meteorological phenomenon) were also included. The second half of the book aimed to provide students with explanations of meteorological data and processes, partly original and partly reproduced from previously published sources, with several chapters on the aurora. The chapter on evaporation is especially relevant to later work as he describes evaporation experiments and concludes that ``water evaporated is not chymically combined with the aerial fluids but exists as a peculiar fluid diffused amongst the rest. At that time it was not 208 necessarily accepted that water vapour has a separate existence in the atmosphere. The book was published by public subscription and Dalton republished it, with almost no changes, some 40 years later, despite the fact that by then some of the ideas in it were out of date. Regional water balance of England and Wales Over millennia people had puzzled over the details of the hydrological cycle and particularly where rivers came from. Around 1700 Edmund Halley still ``considered that condensation in the form of dew and large reservoirs of water in the interior of mountains made a substantial contribution to the water required to maintain the flow of springs. Thus he did not accept the hypothesis of the French writers who immediately preceded him that rain waters are the origin of all springs (Dooge 1974). By the latter part of the century there had been little change in the situation. Dalton set out to rectify this by calculating the water balance for England and Wales. In 1799 he presented his seminal paper on the origin of springs to the Manchester Literary and Philosophical Society. He opened with an elegant introduction: ``It is scarcely possible to contemplate without admiration the beautiful system of nature by which the surface of the Earth is continually supplied with water and that unceasing circulation of a fluid so essentially necessary to the very being of the animal and vegetable kingdoms takes place. Naturalists, however, are not unanimous in their opinions whether the rain that falls is sufficient to supply the demands of springs and rivers, and to afford to the earth besides such a large portion for evaporation as is known to be raised daily. To ascertain this point is an object of importance to the science of agriculture, and to every concern in which the procuration and management of water makes a part, whether for domestic purposes or for the arts and manufactures (Dalton 1802a).

4 He derives an estimate of the annual rainfall as 31 in (787mm), using the short and patchy datasets available at the time and correcting for missing areas, to which he added 5 in (127 mm) for dewfall. Annual evaporation, derived mainly from his own observations on soil-filled containers, was set at 30 in (762 mm). Using a corrected version of Halley s estimate for the flow of the Thames and multiplying this up to account for the other main river basins, he estimated the annual flow to the sea as 13 in (330 mm). These calculations give a discrepancy between input (36 in (914 mm)) and output (43 in (1092 mm)) of 7 in (178 mm). Dalton suggested that this difference could be accounted for mainly from errors in the evaporation (this was a reasonable assumption as confirmed later by Rodda (1963)). Dalton therefore concludes: ``Upon the whole then I think that we can finally conclude that the rain and dew of this country are equivalent to the quantity of water carried off by evaporation and by the rivers. And as nature acts upon general laws, we ought to infer it must be the case in every other country until the contrary is proved (Dalton 1802a). This paper settled for all practical purposes the controversy of the origin of springs and was an important contribution in the development of the quantitative hydrological cycle. It is for this reason that the European Geophysical Society awards the Dalton Medal to leading present-day hydrologists. The evaporation process After leaving the New College, although much concerned with experiments and theories in chemistry, Dalton continued his interest in meteorology and related topics. In the autumn of 1801 he presented three evenings of lectures on the properties of gases, published as four essays in the Society proceedings. In the first essay he describes his method of measuring the temperature dependence of ``the force of vapour from water, i.e. saturated vapour pressure. This was achieved by the introduction of water into a barometer column (containing freshly boiled mercury!) and noting the depression of the column for a range of temperatures. He publishes the resulting table of saturated vapour pressures for a wide temperature range. In his final essay he presents ``a true theory of evaporation. He describes the results of evaporation experiments using containers of water under different temperatures and wind speeds. Explaining that account must be taken of ambient vapour pressure, he formulated his law of evaporation: ``The evaporating force must be universally equal to that of the temperature of the water, diminished by that already in the atmosphere (Dalton 1802b). This can be expressed by the equation E = K (e s ± e a ) where e s is the saturation vapour pressure at water temperature, e a is the vapour pressure of the surrounding air and K is a factor dependent on wind speed. Dalton included a table giving the evaporation rates from water into dry air for a wide temperature range and for low, medium and high wind speeds. This evaporation equation has stood the test of time and is still in use today with suitable values for the factor K. This first successful attempt to estimate evaporation from meteorological data shows Dalton as the pioneering link between the old-school scientists, such as Halley, and modern-day meteorologists. Mountain climatology Dalton was very strict over the matter of holidays but did allow himself a short break every summer ± usually spent ``breathing the salubrious air of the mountains and lakes near my native place in the North of England. His conscience over taking any time off work was eased by combining his visits with scientific data collection, including many energetic mountain excursions investigating whether water vapour really existed separately in the atmosphere (Dalton 1824). The first published set of mountain climate observations are for a descent of Helvellyn in July 1803 ± the temperature at 1300 LT at the summit (855 yards (782 m) above the lake) 209

5 being 55 8F (12 8C) and the dew point 46 8F (8 8C). On reaching the bottom at 1600 LT the temperature was 70 8F (21 8C) and the dew point 53 8F (11 8C). Such apparently basic data conceal a considerable amount of effort as is evident from his account of dew-point measurement: ``The usual mode of my operations was to find a spring on the side of the mountain; then take a cup of water from it and pour it into a clear dry tumbler glass; if dew was produced immediately on the outside of the glass, the water was returned into the cup and the glass was again carefully dried outside. During this time the water was acquiring temperature from the air. It was then returned into the tumbler and held out exposed to the current of air. This process was repeated until no dew was found to be formed on the glass. The temperature of the water each time it was put into the tumbler was found from a small pocket thermometer; and that when it last produced dew on the glass was marked down as the dewpoint (Dalton 1824) (quite a tricky procedure in the lab, let alone on the top of a mountain). He goes on to explain the use of pounded nitre and sal-ammoniac or snow to reduce the temperature if the spring water was not cold enough. In the 1824 paper there are sets of observations for many of the Lake District mountains made between 1803 and Also included is a table setting out the ``drying power of the air according to ambient temperature and dew point. From his observations, Dalton derived useful insight into lapse rates and how water vapour in the atmosphere contributed to the climate of mountains by producing fog and low cloud. In another paper Dalton (1831) analysed data provided from Geneva and the St. Bernard Pass at an altitude of 2720 yards (2487m). There had for some time been attempts to obtain accurate mountain elevations from barometric readings. Dalton carried out many such measurements, the best of which relied on simultaneous pressure readings from two inter-calibrated and temperature-corrected barometers. It was while climbing Skiddaw 210 with his barometer in July 1812 that he first came across the Lake District geologist and guide Jonathan Otley. Subsequently Otley frequently acted as companion and paid guide to Dalton on many of his climbs between 1812 and Otley was also stimulated to collect his own rainfall data at his home town of Keswick (his oak-cased raingauge and built-in measuring cylinder, together with his barometer and other instruments, and the original of his contribution to the biography of Dalton by Henry (1854) can all still be seen at Keswick Museum and Art Gallery). Daily weather records John Dalton made weather observations, generally three times per day, for well over 50 years. In 1819 his first formal summary and analysis covering the Manchester data for the period 1794 to 1818 was published (Dalton 1819). The results included tables of monthly and extreme values of pressure, temperature and rainfall together with remarks on theories of rainfall and its seasonal variation. He also used London barometric data, published by the Royal Society, which he found to ``exhibit marks of extreme carelessness. His paper covering his observations from 1794 to 1840 opened with a note: ``I had occasioned to refer to the transactions of the Royal Society for a series of observations and upon comparison of those with my own, I found reason to believe that the Royal Society s observations and calculations from them, exhibited marks of carelessness which rendered them by no means trustworthy. Some time after this the Royal Society revised their meteorological establishment, and placed it upon a respectable footing, since which, I believe, they may vie with any public body or private individual, in the regularity and accuracy of their observations and tabular results (Dalton 1842). The paper again includes summaries, means and extremes of pressure, temperature and rainfall for the whole period together with some additional rainfall data for other nearby locations. Where necessary, missing data were in-filled using observations from other sources,

6 Dalton not being prepared for others to use his instruments in his absence. Many of the observations were published in the Manchester press and the city made use of them, for instance in choosing the best location for their botanic gardens. Regrettably, few of the original observations are still in existence as most were either lost or destroyed during the bombing of Manchester on Christmas Eve 1940 (Leitch and Williamson 1991). What an interesting resource these records might have been today if they had survived. Other work Dalton s interest, as was typical for scientists of the eighteenth and nineteenth centuries, was not confined to a few subjects. In addition to his main work, he published on botany, geology, physiology and English grammar, and wrote poetry. He famously suffered from severe colour-blindness (often called daltonism) and wrote a definitive paper describing ``extraordinary facts relating to the vision of colours. Conclusion The year 2003 sees the bicentenary celebrations of Dalton s first paper on atomic theory, which led to his international fame. However, his life-long weather studies and his not insignificant contributions to meteorology and hydrology ± in particular his area water balance and evaporation equation ± should not be forgotten in these celebrations. Acknowledgements The authors gratefully acknowledge permission to reproduce the Dalton etching from the Manchester Literary and Philosophical Society, which also publishes the invaluable Dalton bibliography (Smyth 1997). Thanks also to the Kendal Museum and Art Gallery and others for their help. References Dalton, J. (1793) Meteorological observations and essays. Richardson, London and Pennington, Kendal (1802a) Experiments and observations to determine whether the quantity of rain and dew is equal to the quantity of water carried off by the rivers and raised by evaporation; with an enquiry into the origin of springs. Mem. Lit. Philos. Soc. Manchester, V, II, pp. 346± 372 (1802b) Experimental essays on the constitution of mixed gases; on the force of steam or vapour from water and other liquids in different temperatures, both in a Torricellian vacuum and in air; on evaporation expansion of gases by heat. Mem. Lit. Philos. Soc. Manchester, V, II, pp. 535± 602 (1819) Observations of the barometer, thermometer and rain at Manchester from 1794 to 1818 inclusive. Mem. Lit. Philos. Soc. Manchester, second series, III, pp. 483± 509 (1824) Observations in meteorology, particularly in regard to the dew-point, or quantity of vapour in the atmosphere; made on the mountains in the north of England from 1803 to Mem. Lit. Philos. Soc. Manchester, second series, IV, pp.104± 124 (1831) Summary of the rain &c at Geneva and at the elevated station of the Pass of Great St. Bernard. Mem. Lit. Philos. Soc. Manchester, second series, V, pp. 233± 240 (1842) Observations of the barometer, thermometer, & rain at Manchester from the year 1794 to 1840 inclusive being a summary of essays in meteorology. Mem. Lit. Philos. Soc. Manchester, second series, VI, pp. 561± 589 Dooge, J. C. I. (1974) The development of hydrological concepts in Britain and Ireland between 1674 and Hydrol. Sci. Bull., XIX, pp.279± 302 Henry, W. C. (1854) Memoirs of the life and scientific researches of John Dalton. Cavendish Society, Harrison, London Leitch, D. and Williamson, A. (1991) The Dalton tradition. John Rylands University Library of Manchester Manley, G. (1944) John Dalton: 1766± Q. J. R. Meteorol. Soc., 70, pp. 235± 239 Rodda, J. C. (1963) Eighteenth century evaporation experiments. Weather, 18, pp. 264± 269 Smyth, A. L. (1997) John Dalton Manchester Literary and Philosophical Publications Ltd Correspondence to: Dr H. R. Oliver, Harris Manchester College, Oxford OX1 3TD. # Royal Meteorological Society, doi: /wea