454 



^NA TURE 



[March 15, 1894 



with tropical plant life, to go out and mike use of the 

 advantages now so easily within their reach. 



The volume is a most interesting one; it tells of the 

 difficulties which the enterprise of maintaining the 

 •' 's Lands Plantentuin '' had to encounter and to over- 

 come. Founded in 1817, it has succeeded in asserting 

 its value, not only to the colony but also to science, and 

 its importance in the latter respect is testified to by 

 the number of botanists and others who annually visit 

 it, as well as by the large amount of good work begun or 

 carried out in its laboratories. 



The volume, besides containing a description, illus- 

 trated with plans and photographs, of the garden and 

 establishment at Buitenzorg, includes also an account of 

 the various experimental stations which have arisen as 

 offshoots from it. It contains, further, a useful ri'sionc o{ 

 the numerous investigations which have been conducted 

 in connectvon with the gardens, and which have been pub- 

 lished in various journals and reports. There is interesting 

 and valuable information given concerning the culture 

 and uses of economic plants. 



But the gardens in Java, li'<e our own colonial estab- 

 lishments of a similar nature, do not exist solely for 

 scientific or ornamental purposes. Their use to the 

 colony, and their importance in serving as a means for 

 introducing and experimenting on the cultivation of 

 vegetable products suitable to the country, cannot be 

 overrated. The present writer recollects a well-known 

 Ceylon planter observing, a propos of the garden at 

 Peradeniya (in Ceylon), that it would have abundantly 

 justified both its existence and its expense had it done 

 nothing but serve as the means of introducing the culti- 

 vation of Cinchona into the island, during the interregnum 

 which prevailed between the collapse of the coffee in- 

 dustry and the rise of tea. And this remark was the 

 more striking, as it was made some years after experience 

 had been shown that the growth of Cinchona could not 

 be profitably pursued any further. The plant had, 

 however, served its turn, and had saved the country from 

 possible bankruptcy. 



Amongst the list of visitors to the Java garden, one 

 notices the name of Prof. Haberlandt, and he has given 

 us his impressions of the tropics in a most delightful 

 volume. It is true that there is not, perhaps, much that 

 is actually new to any one who is versed in modern 

 botanical literature, but Dr. Haberlandt tells what he has 

 to say in a charmingly enthusiastic and artistic manner ; 

 and his pages are illustrated with impressionist sketches 

 which convey an excellent idea of the character of the 

 objects portrayed. 



The book is what it pro''es5e; to be — an account of a 

 " botanic.il excursion"; bat besides the chapters on 

 epiphytes, mangroves, hill and desert floras, there are 

 sections devoted to observations on the natives and their 

 ways, as well as others on the climate and meteorology 

 of Java. The chief value of the volume lies in the per- 

 ception of things which will, or should, attract the eye of 

 a traveller new to the tropics ; and while the work may be 

 praised as one full of matter of considerable general 

 interest, it may be especially commended to those who are 

 themselves about to undertake a journey to the East. 



J. B. F. 

 NO. 1 272, VOL. 49] 



THE TELEPHONE. 



A Manual of Telephony. (The Specialists' .Series) 

 By W. H. Preece, C.B., F.R.S., and Arthur J. Stubbs. 

 (London: Whittaker and Co., 1893.) 



ONLY about four years ago we reviewed a treatise 

 entitled " The Telephone," by Mr. W. H. Preece 

 and Dr. Maier, which up till recently was the chief manual 

 on its special subject in English. The rapid advance of 

 telephony, however, had rendered large portions of that 

 work completely out of date, and Mr. Preece, with, this 

 time, Mr. A. J. Stubbs as co-worker, has completely re- 

 discussed the subject, and replaced the former treatise by 

 the present. 



The work is divided into six parts, and' each of these 

 again into some half-dozen chapters. Part i. deals with 

 the construction and mode of action of telephones and 

 transmitters, ii. with general apparatus and switches, iii. 

 with simple exchange stations, iv. and v. with the more 

 complicated and extensive exchanges, their switchboards, 

 lie, and vi. with the construction of telephone lines and 

 cables. 



What we said about the merits of the former book we 

 have here to repeat. Nowhere else in English have we 

 so fall and accurate descriptions of telephones and 

 transmitters, or so practical and detailed accounts of 

 telephonic apparatus, and the mode of carrying on the 

 work of telephone exchanges. This, by far the greater 

 part of the book, is extremely well done, and we have no 

 doubt that as a practical guide and help to the telephonic 

 engineer, it will be of very great value. 



Anything we have to say in the way of criticism on the 

 contents of the book resolves itself in the main into a 

 few remarks on the first chapter and the last, in both 

 of which we find sections that seem to require slight 

 improvements. 



In chapter i. we have a very brief account of 

 current induction. This is clear in general, but one 

 or two statements ought to be amplified in order 

 to prevent misunderstanding. On p. 9 it is affirmed 

 that the intensity of the magnetic force in the field of a 

 conductor carrying a current varies inversely as the 

 square of the distance from the conductor. This state- 

 ment cannot be said to be true except of a short current 

 element, in which case the magnitude of the force is as 

 stated, and its direction at right angles to the plane 

 determined by the element and the line joining it to 

 the point at which the force is being considered. 



The conductor contemplated in the next sentence 

 seems to be a straight one of unlimited length, for in 

 other cases the lines of magnetic force are not circles round 

 the wire, unless, of course, the wire be very thin, and the 

 field at points only which are very close to the wire be 

 considered. In the case of a single long straight conductor 

 the magnetic force varies inversely as the distance from 

 the conductor. 



Again, it is stated in p. 1 1, that " there are two classes 

 of induction ' : that is, induction of currents produced by 

 the variation in position or magnitude of currents in 

 neighbouring conductors, and induction due to changes 

 in the magnetic field in which the conductor acted upon 

 is situated. Of course the authors do not mean to assert 



