Dec. 6, 1888] 



NATURE 



and re-condensed by the cold air of the snow-clad 

 summits. The great amount of rain in the border 

 ridges is the more striking as in East Turkestan rain 

 is exceedingly scarce, and there is but very little rain 

 at a level below 6000 feet. Prjevalsky concludes that 

 the heavy summer rains which fall in the Keria Mountains 

 every year are due to the south-western winds coming 

 from the Indian Ocean, and he maintains that the effects 

 of the monsoon winds are felt even in the upper parts of 

 the Hoang-ho. 



From Khotan the Expedition went northwards, across 

 the desert. It crossed the Tarim at the confluence of 

 the Yarkand-daria and the Aksu-daria, at a height of 

 3100 feet above the sea. The river has there a width of 

 185 yards, and an average depth of from 3 to 4 feet at 

 low water. The velocity of the current was 160 feet in a 

 minute. From these facts, as well as from what he saw of 

 the Lower Tarim, Prjevalsky concludes that the river 

 can be navigated by small steamers from Lob-nor up to 

 the confluence of the Yarkand and Aksu Rivers, and that 

 the two latter can also be navigated to some extent. 



The last chapter of the work is devoted to a general 

 sketch of the political condition of Central Asia ; but those 

 who are acquainted with the recent literature of the subject 

 will find little new in it. Geographers who may propose 

 to explore Central Asia will find more to interest them in 

 the introductory chapter devoted to the ways and means 

 of travelling in Central Asia, with minute instructions as 

 to how to organize expeditions. This chapter is full of 

 practical hints. As to the scientific problems, Prjevalsky 

 remarks that the present period of great discoveries 

 in Central Asia is rapidly coming to an end. Few parts 

 of what was formerly the great terra incognita remain to be 

 explored ; so that we approach a time when regular scien- 

 tific expeditions will be necessary. There remain for 

 investigation by means of " scientific reconnoitrings" the 

 plateaus of Northern Tibet, the highlands of Eastern Tibet 

 and Amdo, and Southern Tibet from Lhassa to Gartok. 

 Three expeditions, lasting two or three years each, would 

 suffice for the exploration of these three regions. The 

 Pamir, with the Hindu-Kush and the Karakorum Moun- 

 tains, the Eastern Tian-shan, the Altyn tagh and the 

 Nian-shan, the border-ridges of South-East Mongolia, 

 the whole of the great Khingan, and North-Western 

 Mongolia, close to the Siberian frontier, come next. Deal- 

 ing with the subject of special scientific explorations, he 

 recommends the Karashar and Si-nin for zoologists ; 

 the Tchertchen oasis for archaeologists ; Si-nin for ethno- 

 graphers ; Kashgar and Khotan, and Si-nin and Urga, 

 for meteorologists ; and the whole of Central Asia for 

 geologists. 



The present volume has three maps. One of them, on 

 the scale of 67 miles to the inch, embodies the results of 

 the four journeys of Prjevalsky, and is an excellent map 

 of the eastern parts of Central Asia. Two maps, on the 

 scale of 33 miles to the inch, embody the original surveys 

 of the Expedition at the sources of the Yellow River and in 

 East Turkestan. Numbers of excellent photo-lithographs, 

 and three drawings representing new species of Antelope 

 and Ovis, are inserted in the work. 



Many years will elapse before the complete descrip- 

 tions of Prjevalsky's rich collections will be published. All 

 that can now be said is that they are in excellent hands. 



K. I. Maximowicz, A. A. Strauch, S. M. Hertzenstein 

 E. A. Biichner, A. S. Woeikofl", and A. A. Inostrantsefif 

 are busily occupied with them, and the first parts of their 

 common work are already in print. The first instalment 

 of the first volume, containing the " Mammals," by E. 

 Biichner, was issued at St. Petersburg a few days ago. 



P. K. 



FLOWERING PLANTS OF WILTS. 



Flowering Plants of Wilts ; with Sketches of the Physical 

 Geography and Climate of the County. By th» Rev. 

 T. A. Preston, M.A. 500 pp. With a Map. (Pub- 

 lished by the Wiltshire Architological and Natural 

 History Society, 1888.). 



IN Wiltshire, the chalk downs which form so character- 

 istic a feature of the geology and physical geography 

 of the South of England reach their western limits. The 

 area of the county is about 1300 square miles. It does 

 not anywhere reach the coast, and forms a watershed from 

 which small streams run in three directions, to the Severn, 

 Thames, and English Channel. An elevated plateau of 

 chalk on the south-east occupies more than half the area 

 of the county. This is divided into two unequal halves 

 by a natural depression, called the \'a!e of Pewsey, which 

 runs almost due east and west, from Devizes to Hunger- 

 ford. Along this hollow runs the Kennet and Avon 

 Canal, of which the highest point, near Savernake, 

 reaches an altitude of 500 feet. The northern portion of 

 this chalk plateau is called Marlborough Downs, and the 

 town of Marlborough stands nearly in the centre of it. 

 The southern part is .Salisbury Plain, the word plain as 

 here applied conveying a delusive notion. Salisbury is 

 at the south, and Stonehenge near the centre of this 

 southern chalk tract. The highest points of these chalk 

 downs reach a height of from 800 to 950 feet. The third 

 section of the county, lying west and north of the chalk, 

 is the fertile plain, underlain by greensand and oolite, 

 along which the Great Western Railway runs between 

 Swindon and Bath. The K>;iowing extract from the 

 introductory essay contributed to this flora by the Rev. J. 

 Sowerby gives, in a few words, an excellent idea of the 

 general characteristics of these different districts : — 



" The great characteristic of the chalk plateau is its 

 vast extent of grass-land, where sheep are extensively 

 pastured. This space is more broken up each year for 

 cultivation, but often exhibits great tracts of grass, with 

 only occasional patches of furze. Only on the small 

 patches of Tertiary scattered here and there, especially in 

 the northern part, do we find wood (generally only under- 

 wood), excepting the grand forest of Savernake, twenty 

 square miles in area, which can show timber of an age 

 and size unrivalled in any part of England. The upper 

 chalk hills were once, it is probable, covered with exten- 

 sive copses, chiefly thorns. Remains of these still occur 

 here and there ; and individual trees of great size, some 

 yet extant, others only traditional or historical, attest the 

 former existence of a priniicval wood. In the hollows 

 of the downs, especially near the villages, there are 

 spaces, often finely timbered, especially with elms. 

 Monotonous as the surface of the downs may seem to be, 

 the changes that present themselves are often singularly 

 picturesque and varied. After passing, it may be for 

 hours, over the gently sloping grass plains, all bins above, 

 all green below, the traveller suddenly sees below him a 



