646 



SCIENCE. 



[N. S. Vol. I. No. 20. 



printed in the American Journal of Science 

 and elsewhere, he is the author of the fol- 

 lowing works : 



A System of Mineralogy, 1837, 1844, 1850, 



Zoophytes, 1846. 



Manual of Mineralogy, 1848, 1857, 1878, 

 1887. 



Coral Reefs and Islands, 1853. 



Crustacea, 1852-54. 



Manual of Geology, 1862, 1874, 1880, 

 1895. 



A Text-Book of Geology, 1864, 1874, 

 1882. 



A System of Mineralogy, 1868. 



Corals and Coral Islands, 1872, 1890. 



The Geological Story Briefly Told, 1875. 



Characteristics of Volcanoes, 1890. 



The Four Eocks of the New Haven Ee- 

 gion, 1891. 



CORRESPONDENCE. 

 THE EDUCATION OF THE TOPOGEAPHEE. 



To THE Editoe of SCIENCE : Part of 

 Professor Merriman's review in Science 

 for April 26 interests me as being the 

 direct opposite of my own opinion. He 

 says, apropos of Mr. Gannett's statement 

 that the topographer m.ust be able to gener- 

 alize through his knowledge of geological 

 processes : " These are dangerous doctrines. 

 The earth exists, the duty of the topo- 

 grapher is to map it truly, and the study of 

 the origin of its features should come later." 

 I should like very much to learn through 

 the columns of Science the opinions of 

 other geographers and topographers on this 

 question. 



It is not alone the earth that exists ; a 

 large series of topographical maps of various 

 parts of the earth also exist ; and through 

 their study the young topographer can learn 

 much about the kind of work he will have 

 when surveying those separate parts of the 

 earth that are not yet mapped. This kind of 

 knowledge will help him in mapping new 

 regions in about the same way that prelimi- 



nary study of known forms of plants and 

 animals helps the systematist to describe 

 new forms when he finds them. 



It is certainly the duty of the topogi-apher 

 to make true maps ; but the truest map is 

 always only a generalization. Something is 

 necessarily omitted, and the topographer 

 has to choose between what he shall omit 

 and what he shall represent. He sees 

 many things that he can not map. How 

 shall he be best aided in making on the 

 small sheet of paper before him an expres- 

 sive map of the broad surface of country 

 around him ? I do not say ' an accurate 

 map,' because the word 'accurate' is so gen- 

 erally misunderstood in this connection. 

 It is often taken to imply that the topog- 

 rapher has actually measured every part 

 of the surface of the country and carefully 

 constructed every line on his paper. As a 

 matter of fact, by far the larger part of all 

 maps is sketched, and in the sketching more 

 facts often have to be omitted than can be 

 represented. Hence, everything should be 

 taught to the topographer that will aid him 

 in really seeing the facts that are before 

 him and faithfully representing such of them 

 as come within the limit of the scale he em- 

 ploys. 



Nothing is of more assistance in seeing 

 the facts, and in thus making a good begin- 

 ning towards sketching them properly, than 

 some understanding of their origin and 

 meaning. Hence I believe that the best 

 course of education for topographei-s while 

 yet in school should include a careful study 

 of the development of land forms, and that 

 the best practical work by topographers 

 will require a very careful and sympathetic 

 study of the origin of the land forms on 

 the ground before him. The prepossession 

 that contour lines bend up-stream has de- 

 ceived manj' a topographer into giving a 

 wrong expression to flat alluvial cones. In- 

 difierence to the significance and impor- 

 tance of the sharp edge of a gorge or a cliff 



