740 EEPORT — 1895. 



of their origin. The ' ant-hills,' elsewhere sown evenly over the land-surface, ar3 

 in certain parts drawn into chains and foreshortened, or in modern railway parlance 

 ' telescoped.' One step more— the confusion of the lines of slope-shading with those 

 of hill-outline— and the pictures would he conventionalised, all signs of origin 

 would he lost, and students who had never seen a great mountain-range would be 

 led to think of it as a wall-like ridge. Even ' ant-hills ' are preferable to the 

 ' caterpillar' in its crudest form. 



An indication of the importance attached to the new problem of relief is to be 

 seen in the fact that, before the metliod of hill-shading or hatching had been perfected, 

 the method of horizontal contouring had already been invented. In 17;:i7 Philip 

 Buache, a French geographer of remarkably original mind, produced a contoured 

 chart of the English Cbannel. Contour lines represent what would be coast lines 

 were the sea to rise or fall to the level indicated, and it was natural that this device 

 should first be applied to the mapping of the sea-bed rather than the land. In 

 1791 Diipain Triel drew a contoured map of France. But already in 1783, as Mr. 

 Ilavenstein pointed out in his address at the Carditi' meeting, Lehmann had com- 

 bined the two systems, and, by superimposing hachures upon contours, and making 

 the depth of shading proportional to the closeness of the contours, had produced 

 a map which, while yielding to the popular requirements, rested on a scientific 

 basis. Contoured maps, in which names are few or absent, can now, however, be 

 made to rival in pictorial suggestiveness those which are shaded, and such maps 

 are the more valuable in that they are not only structurally correct, but that they 

 can be read also with accuracy and ease. Some of the sheets (if the American 

 Geoo-raphical Survey may be cited as e.vcelleut examples of graphic effect produced 

 by contours only. 



Ptolemy's knowledge of the theory and methods of cartography far outran the 

 positive materials at his command for the mapping of the known world. In the 

 same way the methods of depicting relief, though so recently developed, already at 

 the end of last century more than sufficed for the presentment of the recorded data. 

 As was seen in the case of Ptolemy, there are peculiar dangers in the possession of 

 an engine more powerful than is needed for the work in hand. In 1788 Frnace 

 was the only country in the world with a completed map based on systematic and 

 detailed surveys. A relief-map like that of Dupain Triel was possible only in 

 such a country. But in 175G Philip Buache had already launched a general theory 

 of relief resting on the conception of river basins, and had enriched geography 

 with the terms ' water-parting ' and ' plateau.' In the absence of positive know- 

 ledge, what more natural than that cartographers should make illegitimate use 

 of the theory of Buache, and should assume that in the coherent system of water- 

 partings they had the orographical skeleton of the world ? Having drawn the 

 courses of the rivers, they had only to run caterpillar-shading along the water- 

 partings to produce a map, in parts accidentally true, which represented the land 

 as uniformly composed of a series of flat pans. Such a method of map-drawing 

 was advocated by Friedrich Schultz, in a paper published at Weimar as late as 

 1803, and is not rare in popular maps of much later date. 



It is to Ale.'cander von Humboldt that we owe the method still in use for giving 

 a general, yet real, idea of the relief of a little known country. Following, as he 

 himself tells us, the precedent of the canal engineers, he constructed vertical sec- 

 tions along his routes through Spain and Mexico. It is worth noting in this 

 connection that our knowledge of the relief of the sea-bed is mainly due to the 

 requirements of another set of engineers — those engaged in laying telegraphic 

 cables. Humboldt's sections were rendered possible by the daily use of the baro- 

 meter and chronometer, and by Ramond's improvement of the formula for the 

 reduction of barometric data. Before Humboldt, the barometer had been used 

 for the determination of isolated heights, but not for the traversing of a whole 

 country. 



Turning now to the other basis of scientific geography — a knowledge of the 

 fluid circulation in the outer envelopes of the earth — we may regard the corner, 

 stone of climatology as laid by George Hadley in 1735, in his well-known paper 

 before the Royal Society, ' Concerning the Cause of the General Trade Winds.' 



