June 20, 1895] 



NA TURE 



171 



•one <'/^(r//-/V(z/ horse-power. In the chapter on the power 

 of the wind, there is an interesting description of an 

 electrical plant for lighting, which was used in London 

 some time ago, the motive power being a windmill on the 

 top of the building. There apjjcars to be an opening for 

 this type of motor. The author gives rales and tables for 

 their design and construction. 



Water-wheels, turbines, and hydraulic motors generally 

 come in for a good deal of notice. The information given 

 concerning^ these motors is very much condensed, but is 

 in a useful form. " Molesworth's Pocket-book " is quoted 

 for rules for the actual construction of turbines ; Bodmcr's 

 book can be added with advantage. The question of 

 labour and attendance has to be carefully considered in 

 connection with the adoption of steam-power ; a type of 

 motor which, for small powers, is being discarded in favour 

 of oil and gas engines. The steam engine, however, has 

 points in its favour, simplicity of parts being not the least 

 of them. The author gives a table showing relative values 

 for heating purposes of various fuels ; this is of vrUie, and 

 may pro\e of use to many steam users. 



llnder the heading of liquid fuel, no observations are 

 to be found describing " Holden's -System" for burning 

 oil, tar, &c. ; this should be added in a future edition. 

 An essential feature of this work is a statement of 

 the probable cost of the machinery described, thus 

 rendering a comparison possible of alternate schemes. 

 The condensation of exhaust steam from engines in large 

 towns is an imijortant ([uestion, because in some cases 

 it may become a nuisance. The author describes the 

 usual methods in vogue, but omits to mention the 

 atmospheric condenser used to condense the steam, 

 and so get rid of it. .Steam engines of various kinds 

 are fully dealt with, including those suitable for 

 dynamo driving. Under the latter class we find no 

 description of the Willan's central valve engine, probably 

 the most efficient of any. If chapter x.\i. is intended to 

 include this engine, why not say so ? 



The author has much to say on the subject of different 

 types of boilers. On page 179 we find a table giving 

 the pitch of stays in flat surfaces in locomotive fire-boxes. 

 This requires considerable alteration. The pitches given 

 for the higher pressures and i-inch plates are ridiculous ; 

 no locomotive builder exceeds 4^- inches pitch with copper 

 fire-boxes. The usual hydraulic test for boilers is stated 

 to be twice the working pressure. This is so in many 

 cases, and we agree with the author that the boiler is 

 needlessly strained. One and a half times the working 

 pressure is ample, and is quite sufficient to test the 

 w orkmanship. As to the general essentials for good boiler 

 work, given on page 181, we cordially agree, but would 

 add that machine flanging should, if possible, be done 

 at one heat. 



Much has been said of late about the virtues of the 

 tubulous boiler. No doubt its convenience of transport 

 is great, repairs are easily effected, and steam can be 

 rapidly raised. The author gives some interesting data 

 on these boilers, including the Belleville type now being 

 adopted in this country. 



Users of small power motors will be interested in 

 chapter xxx. <•/ scq. These deal with gas and oil engines, 

 and contain some interesting information. Taken as a 

 NO. 1338, VOL. 52] 



whole, this book contains a serviceable collection of data 

 on various subjects. The volume should prove of use to 

 engineers, who will find in it much information relative 

 to motive powers. N. J. L. 



TRAVELS IN TIBET. 



Diary of a Journey tltrotigh Mongolia and Tibet in 1 89 1 

 andi&()2. By William WoodvilleRockhill. 8vo. Pp. 

 x.x. and 414. Illustrations. (Washington : published 

 by the Smithsonian Institution, 1894.) 



MR. ROCKHILL is no stranger to the British public; 

 his admirable work on Tibet — " The Land of the 

 Lamas," published in 1891— has been widely read, and 

 his second great journey, described in the book now 

 before us, earned for him the gold medal of the Royal 

 Geographical Society, the highest geographical prize in 

 the world. The book, as now published, differs from 

 "The Land of the Lamas" by being less a piece of 

 literature for general reading than a compendious record 

 of observations suited for serious students of Central 

 Asia. 



Tibet is peculiar amongst the regions of the world by 

 possessing ahnost every possible barrier to discourage the 

 would-be explorer. Its physical conditions, lying in the 

 centre of the largest continent, raised, though just with- 

 out the tropic, into the frigid zone of altitude, composed 

 in large part of rainless arid plains, girdled by the most 

 stupendous mountains of the earth, conspire with the 

 fanatical exclusi\eness of its governing body to keep 

 the land in seclusion. There have been fewer travellers 

 in Tibet than in almost any other area of the known 

 world. In his preface Mr. Rockhill recalls the deeds of 

 his predecessors from Friar Oderic in 1325 to the Russian, 

 French, and British travellers of the last decade. The 

 last Europeans to reach the capital city of Lhasa were 

 the Lazarist fathers, Hue and Gabet, in 1846. Since 

 then the Indian native surveyor, Sarat Chandra Das, 

 has succeeded in disguise in making a survey of the 

 town, but e\ery European has been successfully stopped 

 and turned back at the entrance to Lhasa territory. 

 Mr. Rockhill was no more fortunate in evading this 

 fiite than his predecessors were, or than his successor, 

 Miss Annie Taylor, has been ; but he was fortunate in 

 being able to give 'an excellent account of the portions 

 of the country which he visited. Mr. Rockhill has the 

 almost unique attainment of knowing both the Chinese 

 and the Tibetan literary languages perfectly; consequently 

 he was able to make his own negotiations with the 

 natives, and to obtain information from them at first 

 hand. It is gratifying to find that one result of his 

 careful study of Tibet is to vindicate the general truth- 

 fulness of the Abb^ Hue's picturesque description of 

 the country and the people, which is really responsible 

 for such popular knowledge of Tibet as exists in European 

 literature, and on which some recent travellers, misled 

 by bad interpreters, had cast serious doubts. 



Mr. Rockhill describes his journey in the form of a 

 diary, a form which throws all the details mto equal and 

 somewhat undue prominencc,dcmanding very careful read- 

 ing, and many references to different passages, before the 



