78 



N^ATURE 



[September 15, '1921 



the author, proceeds to discuss the action of nitric 

 acid onchlorobenzene, and of chlorine on nitro- 

 benzene. It is well known that in the first case 

 ;^,jnvxture of ortho- and para-derivatives results, 

 Avhereas in the second case a meta-compound is 

 formed. As negative chlorine is present in the 

 nucleus, positive NO., will naturally replace posi- 

 tive hydrogen, giving 



CI 



NO, 



CI 



\. 



NO., 



In the second case, where positive NO2 is already 



- + 

 present in the nucleus, and is acted on by CI. CI, 



it is not CI which is now, as it were, received into 



the family circle, but his brother, CI, which there- 

 fore enters the meta position. One becomes a 

 little bewildered with the . sudden volte-face 

 exhibited by the differently charged atoms. 



The present writer has no wish to do any in- 

 justice to Prof. Fry's, theory. There is no doubt 

 that it contains a substantial germ of truth ; it 

 explains many facts of substitution, and is suffi- 

 ciently elastic to undergo almost unlimited ex- 

 tension provided all the postulates are accepted. 



J. B. C. 



Along the Snow-line of Peru. 



The Andes of Southern Peru: Geographical Re- 

 connaissance along the Seventy-third Meridian. 

 By Isaiah Bowman. First English edition. 

 Pp. xi -h 336. (New York : The American Geo- 

 graphical Society of New York ; London : Con- 

 stable and Co., Ltd., 1920.) 275. 6d. net. 



THIS pleasantly written, highly interesting, 

 and well-illustrated book by the director of 

 the American Geographical Society is one of the 

 results of the Yale Peruvian Expedition of 191 1. 

 Its theme was a reconnaissance of the Andes along 

 the 73rd meridian. The author was responsible for 

 the making of a contour map. The north-to-south 

 journey from the 12th to the 17th degree of south 

 latitude cuts the Andes obliquely across from 

 the tropical rubber-producing plains of the lower 

 Urubamba, north-west of Cuzco, southwards over 

 snow-covered passes to the desert coast of 

 Camana. For weeks the party laboured across 

 and along bleak, lava-covered country, without 

 interruption, at the uncongenial elevation of be- 

 tween 14,000 and 18,000 ft. 

 NO. 2707, VOL. 108] 



The second part ©f the present volume deals 

 with the physiography of the Western and Eastern 

 Andes, the coastal terraces, geologic development, 

 and glacial features, with many maps and pro- 

 files. Other chapters — e.g., those on climatology 

 and meteorological records — are also necessarily 

 severely technical, but the first part of the book 

 is eminently readable, and instructive from a broad 

 point of view. It is entitled "Human Geography," 

 and the author endeavours to show the effect of 

 environment upon mankind in the widest sense. 

 Witness the chapter entitled "The Geographic 

 Basis of Revolutions and of Human Character in 

 the Peruvian Andes." Many of the points raised 

 may appear obvious, others somewhat far-fetched 

 or laboured, and yet they cause us to ponder, and 

 in not a few instances the author makes good his 

 claim' by tracing cultural, political, and other con- 

 ditions to their respective sources — very obvious 

 when pointed out, but requiring a broad mind, 

 open eyes, and travelled experience. 



" It is pleasant to think that the tropical forest 

 may be conquered. It is nonsense to say that 

 man now conquers it in any comprehensive and 

 permanent way. The tropics must be won by the 

 strong hands of the lowlier classes which are ig- 

 norant and careless of hygiene. W^e cannot sur- 

 round every labourer's cottage with expensive 

 screens, oiled ditches, and well-kept lawns. . . . 

 Travel in the desert is a conflict between heat 

 and aridity, but travel in the tropical forest is a 

 struggle against spaces, heat, and a superabun- 

 dance of all but useless vegetation." 



The regional diagrams introduced are most 

 instructive — e.g. Fig, 25 : 



" When amplified by photographs of real 

 conditions, such a diagram becomes a sort 

 of generalised picture of a large group of geo- 

 graphical facts. ... It would be a real service to 

 geography to draw up a set of, say, a dozen 

 regional generalised diagrams for a whole con- 

 tinent." 



The expedition came across the loftiest 

 habitation in the world. It was crossing at 

 17,400 ft., and 300 ft. lower was the last outpost 

 of the Indian shepherds, built of stone and 

 thatched, sheltering a family of five, with three 

 fat, rosy-cheeked children. Less than 100 ft. 

 below were other huts, and flocks of alpaca and 

 sheep. 



The snow-line is here at the surprisingly high 

 level of between 17,200 and 17,600 ft. Potatoes, 

 small and bitter, but edible, and a variety of maize 

 grow up to 17,400 ft., where they endure repeated 

 frosts. "Perhaps the Indians have arrived at 

 results ahead of those by our professional experi- 

 menters." 



I 



