NATURE 



545 



THURSDAY, OCTOBER 8, 1903. 



MILITARY TOPOGRAPHY. 

 Recherches sur les Instruments, les Methodes et le 

 Dessin Topographiques. By le Colonel A. Lausse- 

 dat. Tome ii., part ii. Pp. 287. (Paris : Gauthier- 

 Villars, 1903.) 



THE second volume of Col. Laussedat's exhaustive 

 work on topography, which has just been pub- 

 lished, deals with the art of metrophotography as 

 developed in Europe generally and in France in par- 

 ticular; condensing the opinions and experiments of 

 leading men of science, and epitomising their results. 

 Attempts to adapt the principles of natural perspective 

 to topography in France date from the middle of the last 

 century. French methods were adopted by Germany 

 in 1865; Italy followed suit in 1875; ^"<^ ^" Austria, 

 Maurer executed a military reconnaissance of some 

 importance (which could have been attained in no 

 other way) in 1887. There has gradually accumulated 

 ,1 large amount of scientific literature in .Austria deal- 

 ing with this subject; and in 1889 the Swiss engineer 

 S. Simon had made a photographic survey of Jung- 

 frau. Russia has been busy for many years in the 

 Trans-Caucasus and in Persia, working on similar 

 methods to those of Switzerland, whilst Greece, Brazil 

 and Madagascar have all contributed results of 

 ^ -ientifiic value towards the development of the art. 

 Spain has been interested since 1863, and in 1899 an 

 " excellent ouvrage " was produced in Madrid by two 

 ( ngineers, Iriarte and Navarro, which seems to have 

 been the most complete work on the subject up to 

 the date of Laussedat. 



New Zealand and Australia have not been idle ; 

 l)ut amongst our colonies it is to Canada chiefly that 

 we look for the most practical experiments leading to 

 the most noteworthy results in this as in every other 

 branch of topographic art. In the United States as 

 early as 1886, photographic methods for rapid recon- 

 naissance were taught at West Point; but it is to the 

 Canadian experts, Deville and Fleurer, that we owe 

 most of our practical knowledge. A general summary 

 of Canadian results will be found in Wilson's useful 

 work on topographic art. 



England and English surveyors alone contribute 

 nothing to the world's knowledge ot this branch of 

 surveying, although of all countries in the world 

 England is probably most interested in its develop- 

 ment. Colonel Laussedat, noting that as early as 

 1869 Colonel J. Baillie proposed that photography 

 should be utilised as an aid to reconnaissance, suggests 

 that the absence of all result may be due to the fact 

 that its military application precluded it from public- 

 ation — " il est probable que des r^sultats d la fois 

 curieux et utiles ont pu etre obtenus dans un ordre 

 d'id^es qui ne se prete pas k la publicity." Biit he is 

 probably unaware that the preliminary art of topo- 

 graphy is as yet undeveloped in England ; and that we 

 are still a long way from the scientific consideration 

 of any of its more subtle branches. It is true that 

 in India (where the knowledge of topography is an 

 every day practical necessity) some experiments have 

 NO. 1771, VOL. 68] 



been made with the Bridges-Lee instrument (the 

 phototheodolite), but there are good reasons why 

 photography as an aid to surveying should only be 

 applicable in exceptional cases and under exceptional 

 conditions in that country. The ultimate practical 

 value of metrophotography lies in the power which 

 it places in the hands of one accomplished topo- 

 grapher to do the work of many. It is a financial 

 question in the long run, but, as Col. Laussedat does 

 not fail to point out, it is useless in the hands of an 

 amateur. It requires a surveyor (or an artist) of ex- 

 ceptional ability and experience as a topographer to 

 render it effective. Workmen of this stamp are rare 

 anywhere and command good value for their work. 

 In India the simpler form of topography attained by 

 the use of the plane table (which is invariably superior 

 in its final results to those of metrophotography when 

 applied to ordinary country by ordinary workmen) is 

 attained cheaply and satisfactorily ; for the native 

 labour of India is cheap, abundant, and specially 

 adapted by nature to this form of art. Metrophoto- 

 graphy, therefore, would probably not pay. 



The practical application of metrophotography has 

 been well exemplified by Le Bon in India, in aid 

 of archaeological research ; by Legros as an explorer ; 

 by Vallot as a mountaineer (in which direction it is 

 specially useful), and by many other Frenchmen in 

 various ways in different parts of the world, leaving 

 no room for doubt as to its value in exceptional 

 circumstances, and the necessity tor its continued 

 development. But Laussedat is at some pains to 

 quote the opinion of the Canadian expert Deville, who 

 proves clearly the limitations of the art, and shows 

 that photographic topography is just as much de- 

 pendent on accurate preliminary triangulation as any 

 other form of topography. He enters fully into the 

 difficulties which beset the method, both as to the 

 determination of scale and the representation of 

 orographic features by contours. 



A variety of new instruments designed to aid in 

 the reduction of photographs to plan are described, 

 and the scientific principles involved in their con- 

 struction are discussed at length — such as the trir^gle 

 of Nicholson, the perspectograph of Hermann Ritter, 

 Hanck's apparatus, and the perspecteur panoramique 

 of Ch. von Ziegler. Some of the problems offered for 

 the consideration of his readers are of considerable 

 mathematical complexity. A good deal has been 

 added to that which has already appeared in vol. i. 

 on the subject of telephotography (which was em- 

 ployed with so much success by engineers during the 

 siege of Paris), and forms a particularly fascinating 

 chapter in this work. 



A chapter on balloon and kite flying reconnaissance, 

 with an inquiry into the nature of the instruments 

 used and of their attachments, as well as into the 

 principles involved in determining the scale of the 

 resulting photograph and in the reduction of observ- 

 ations, is interesting; although it is difficult to believe 

 that automatic observations taken from flying kites 

 or balloons can be made valuable for military purposes 

 unless applied to the illustration of positions within 

 which two or three points have been accurately fixed 



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