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Churchman's Contours ?
- By The Map Collector
- Published 1 March 1986
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The Map Collector
The Map Collector, initiated by Peter Scott and Valerie G. Newby, was a journal on historical cartography published every quarter. The first issue appeared in 1997 and continued for nearly 20 years. After 74 issues the last copy appeared in Spring 1996. Mrs. Valerie G. Newby, is presently editor of the IMCoS Journal.
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by William Ravenhill (Department of Georaphy at Exeter University)
THE CONCEPT OF the isoline, as a line along which values are assumed to be constant, emerged in the last quarter of the sixteenth century and developed into the contour line in the last quarter of the eighteenth century. Credit for this latter extension and application of the idea is given to the French cartographers particularly as a result of the work of Francois de Dainville. The subsequent translation of his 'De la profondeur a l'altitude' into English by A. H. Robinson has done much to make this important article available to the English-speaking world and thereby to strengthen the claim of primacy for the French. It is never easy to disentangle the strands in the innovation and diffusion of an idea or to discern the originating mind in the extension of a concept, nevertheless the task is often well worth the effort, hence the interest aroused by recent work on historical glossaries of cartographic terms.
Among such terms calling for more than usual attention is the contour line owing to its immense importance in modern cartography. According to de Dainville, the idea of transforming a 'plan of soundings' into an exact `bathymetric contour plan' is given to a young French lieutenant by the name of J. B. Meusnier in 1777. His method was first practised in taking the soundings of the Cherbourg roadsteads in 1789. This was, however, still a marine chart. A Languedocian, M. du Carla, applied the same idea to land as well as sea and this was expressed in an experimental hypothetical map to illustrate the problem in a work published in 1782 by Dupain-Triel at Paris.' In 1801 Battalion Commander Haxo, Chief of staff of the Engineers of the army in Italy, made the first terrestrial application of the Meusnier method by contouring, with an interval of two metres, the site of Rocca d'Anfo on the shores of Lake Idro. This happened to be an important military site which Bonaparte wished to fortify. Contouring required a number of techniques to be applied together and the operational difficulties involved made it rather impracticable for the surveys of large areas. A Commission was set up in Paris in 1802 charged to simplify and bring uniformity to the conventions in use on French maps and cartographic plans. After examining the three methods of representing relief — that is perspective drawing, contours and lines indicating the steepest slopes — the Commission decided in favour of the latter. While members of the Commission recognised the value of contours the instruments to carry out the task satisfactorily were not available. In fact, it was not until 1809 that a Captain Clerc made progress in this respect by suggesting the use of a compass to which was fixed a bubble-level; an instrument of this kind would enable the double operations of mapping and levelling to be undertaken simultaneously. Captain Clerc's work is therefore regarded as marking, in the years 1809-1813, the very threshold of modern relief representation by accurately-defined contour lines.
The years 1760-1815 were, however, troubled ones throughout Western Europe involving much military activity and preparedness. Such periods in history are conducive to investment both of money and manpower in cartography triggering off experimentation and field-work. Britain was no exception in this respect and the first recorded use of contours appears to fit not only into this era but also to coincide in time with the work undertaken by the Frenchman J. B. Meusnier.
In the years 1774, 1775 and 1776 Charles Hutton ER.S. 'by the direction and partly under the inspection of the Rev. Nevil Maskelyne D.D., ER.S. the astronomer royal' undertook a survey of the mountain called Schehallien in Perthshire in order to ascertain the mean density of the earth. It was a detailed survey involving a very large number of observations and calculations which in the end produced data to provide not only a large-scale plan but also 'near 1000 points, whose places in the plan and relative altitudes have been computed.'I° The next stage, to calculate the effect of the mountain on the deviation of the plumb-line 'at first gave much trouble and dissatisfaction' till Hutton 'fell upon the following method by which the defect was in great measure supplied, and 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. Although he drew these contours for the purposes of calculation, the map he published to illustrate his paper was but a small-scale derivative of his larger plans and, unfortunately for the progress of cartography, it did not have contours but relied on hachures 'to convey', as he intended, 'a general idea of the nature of the ground.'
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COPYRIGHT March 1986 The Map Collector, All rights reserved.
No portion of this article nor the accompanying illustrations can or may be reproduced without the express written permission from the copyright holder.
THE CONCEPT OF the isoline, as a line along which values are assumed to be constant, emerged in the last quarter of the sixteenth century and developed into the contour line in the last quarter of the eighteenth century. Credit for this latter extension and application of the idea is given to the French cartographers particularly as a result of the work of Francois de Dainville. The subsequent translation of his 'De la profondeur a l'altitude' into English by A. H. Robinson has done much to make this important article available to the English-speaking world and thereby to strengthen the claim of primacy for the French. It is never easy to disentangle the strands in the innovation and diffusion of an idea or to discern the originating mind in the extension of a concept, nevertheless the task is often well worth the effort, hence the interest aroused by recent work on historical glossaries of cartographic terms.
Among such terms calling for more than usual attention is the contour line owing to its immense importance in modern cartography. According to de Dainville, the idea of transforming a 'plan of soundings' into an exact `bathymetric contour plan' is given to a young French lieutenant by the name of J. B. Meusnier in 1777. His method was first practised in taking the soundings of the Cherbourg roadsteads in 1789. This was, however, still a marine chart. A Languedocian, M. du Carla, applied the same idea to land as well as sea and this was expressed in an experimental hypothetical map to illustrate the problem in a work published in 1782 by Dupain-Triel at Paris.' In 1801 Battalion Commander Haxo, Chief of staff of the Engineers of the army in Italy, made the first terrestrial application of the Meusnier method by contouring, with an interval of two metres, the site of Rocca d'Anfo on the shores of Lake Idro. This happened to be an important military site which Bonaparte wished to fortify. Contouring required a number of techniques to be applied together and the operational difficulties involved made it rather impracticable for the surveys of large areas. A Commission was set up in Paris in 1802 charged to simplify and bring uniformity to the conventions in use on French maps and cartographic plans. After examining the three methods of representing relief — that is perspective drawing, contours and lines indicating the steepest slopes — the Commission decided in favour of the latter. While members of the Commission recognised the value of contours the instruments to carry out the task satisfactorily were not available. In fact, it was not until 1809 that a Captain Clerc made progress in this respect by suggesting the use of a compass to which was fixed a bubble-level; an instrument of this kind would enable the double operations of mapping and levelling to be undertaken simultaneously. Captain Clerc's work is therefore regarded as marking, in the years 1809-1813, the very threshold of modern relief representation by accurately-defined contour lines.
The years 1760-1815 were, however, troubled ones throughout Western Europe involving much military activity and preparedness. Such periods in history are conducive to investment both of money and manpower in cartography triggering off experimentation and field-work. Britain was no exception in this respect and the first recorded use of contours appears to fit not only into this era but also to coincide in time with the work undertaken by the Frenchman J. B. Meusnier.
In the years 1774, 1775 and 1776 Charles Hutton ER.S. 'by the direction and partly under the inspection of the Rev. Nevil Maskelyne D.D., ER.S. the astronomer royal' undertook a survey of the mountain called Schehallien in Perthshire in order to ascertain the mean density of the earth. It was a detailed survey involving a very large number of observations and calculations which in the end produced data to provide not only a large-scale plan but also 'near 1000 points, whose places in the plan and relative altitudes have been computed.'I° The next stage, to calculate the effect of the mountain on the deviation of the plumb-line 'at first gave much trouble and dissatisfaction' till Hutton 'fell upon the following method by which the defect was in great measure supplied, and 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. Although he drew these contours for the purposes of calculation, the map he published to illustrate his paper was but a small-scale derivative of his larger plans and, unfortunately for the progress of cartography, it did not have contours but relied on hachures 'to convey', as he intended, 'a general idea of the nature of the ground.'
Read Full Article >>
[Acrobat Reader required]
COPYRIGHT March 1986 The Map Collector, All rights reserved.
No portion of this article nor the accompanying illustrations can or may be reproduced without the express written permission from the copyright holder.
