May 2, 1878] 



NATURE 



II 



OUR BOOK SHELF 



Familiar Wild Flowers. Figured and Described by F. 

 E. Hulme, F.L.S., F.S.A. With Coloured Plates. 

 Parts I.-XIII. (London : Cassell, Petter, and Galpin.) 



There has certainly been a wonderful improvement of 

 late years in the art of chromo-lithography as applied to 

 botanical illustrations ; and the specimens in the work 

 before us are among the best that we have seen. The 

 colouring, the outline drawing, and the general repre- 

 sentation of habit, are all remarkably true to nature. The 

 floral initial letters and tail-pieces, which are stated to be 

 drawn "by various artists," are not so uniformly success- 

 ful. Each part, published at the remarkably low price 

 of sixpence, contains two coloured plates, more than one 

 species being occasionally placed on a plate. The accom- 

 panying letter-press descriptions, though rather shorter 

 than would in many cases be desirable, are written in plain 

 and easy and not too technical language. There is no indi- 

 cation of the proportion of the British flora intended to 

 be included under the designation of "familiar wild 

 flowers ; " but whenever the volume is completed, it will 

 be a useful addition to our popular botanical literature, 

 and well calculated to promote an accurate knowledge of 

 the common plants of our fields and hedges. 



Heroes of South African Discovery. By N. D'Anvers. 

 (London : Marcus Ward and Co., 1878.) 



, The Countries of the World. By Robert Brown, M.A., 

 Ph.D., &c. Vol. ii. (London: Cassell. No date.) 



The Life of Sir Martin Frobisher. By the Rev. Frank 

 Jones, B.A. (London : Longmans, 1878.) 



There seems to be no end to the number of geogra- 

 phical works published nowadays. Mr. D'Anver's 

 work is a companion volume to " Heroes of North 

 African Discovery," by the same author, already noticed 

 by us. Like its predecessor its numerous pictures and 

 the many adventures of the "heroes" of its pages will 

 render it attractive reading for boys, who, if they read 

 it faithfully, will carry away with them much valuable in- 

 formation. The work does not pretend to anything like 

 minute research, but so far as it goes, it is, we believe, 

 trustworthy. 



The present volume of Dr. Brown's work, which may 

 be taken as a typical specimen of Messrs. Cassell' s showy 

 popular publications, deals mainly with the United States 

 and Mexico. Dr. Brown has taken considerable trouble to 

 obtain varied information concerning the different States, 

 and his account of them is fairly full and accurate. In a 

 work like this he cannot be blamed for repeating the oft- 

 told story of his adventures in the west and north-west, 

 though the style, rather than the stories, pall somewhat 

 on one. The pictures, we believe, maybe taken as on the 

 whole what they purport to be ; though it is curious to 

 notice the uniformity of Nature under different conditions, 

 and at widely separated places. One of the illustrations 

 connected with Mexico is entitled a " Lagoon in the 

 Sierra Calientes." Dr. Brown will be interested to know 

 that an exactly similar scene is pictured as occurring on 

 the banks of the Ucayli in South America, in " Paul 

 Marcoy' s " Travels ; but as it is doubtful if " Paul 

 Marcoy " was ever many miles from Paris, the "Scene on 

 the Ucayli" may be as mythical as his "Travels." 



Judging from the formidable list of authorities given 

 by Mr. Jones, his life of the rough, but brave and' even 

 chivalrous old Frobisher must be the result of much 

 research. Mr. Jones seems, however, to be entirely defi- 

 cient in literary skill ; his materials hare been put together 

 in the crudest manner possible. Though Frobisher added 

 little to geographical knowledge, he deserves a place 

 among the heroes of the North-West Passage for his 

 three attempts to discover it. Unfortunately the object 



of his last two expeditions was to bring home shiploads 

 of the "black earth" which people had been deluded 

 into believing was rich in gold, and all Frobisher' s efforts 

 at discovery were balked. His life deserved to be 

 written, but we cannot say that Mr. Jones has_ shown 

 himself competent for the task. 



LETTERS TO THE EDITOR 



\The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of rejected manuscripts. 

 No notice is taken of anonymous communicatiotu. 



[ The Editor urgently requests correspondents to keep their letters as 

 short as possible. The pressure on his space is so great that it 

 is impossible otherwise to ensure the appearance even of com' 

 munications containing interesting and novel facts.'\ 



The Telephone 



The following experiments lately made as to the use of the 

 telephone in connection with a magneto -electric machine, have 

 given results which are somewhat interesting. 



In the first instance a small medical magneto -electric machine 

 was employed with the result (described by Mr. A. Percy Smith, 

 Nature, vol. xvii. p. 380), of a loud click at each rotation 

 of the bobbins in front of the magnet. Driving the former by 

 means of a small turbine, the clicks combined to form a loud 

 musical note which rose and fell as the speed of rotation was 

 increased or diminished. This note was well heard through a 

 resistance of 32,000 units. 



A magneto-electric exploder having two horseshoe' magnets, 

 four bobbins, and two rotating armatures was next employed. 

 This gave a loud sound through S7,ooo units of resistance. 

 With a view to test the power of the machine to work through 

 bad insulation, it was tried through about thirty yards of bare 

 copper wire lying on wet grass. The sound was still powerful. 



A break was then made in the line by cutting it across and 

 dipping the two ends in a fountain basin filled with water. The 

 two ends in the water were about twelve feet apart, and the 

 sound was still perfectly audible. It was found in this experi- 

 ment that it was not necessary to connect the magnetic exploder 

 to earth, and that a sound feebler, but quite distinct, was 

 obtained when only a single wire was led from it. The line was 

 thus from exploder through twelve feet of water to telephone, 

 the other binding screw being connected to a wire simply touch- 

 ing the wet gravel, there being therefore no return line. 



Again the exploder and telephone were connected to a 

 stretched wire belonging to a fence, at a distance apart of about 

 fifty yards. The wire was supported by fifteen intermediate iron 

 uprights with their ends buried in the ground. Earths were 

 made for the telephone and exploder by means of a clasp knife 

 and a little garden fork. A perfectly distinct sound was heard. 



Lastly, one terminal of the exploder and telephone were con- 

 nected by a wire, the others being joined by a length of twenty- 

 four feet of thin string dipped into river water and subsequently 

 drawn through a dry cloth. An audible sound was noticed. 



The above experiments seem to point to two conclusions : — 



1. That magneto -electric currents can be employed through 

 exceedingly defective insulation, almost no insulation, in fact. 



2. The omission of the earth connection of the exploder 

 seems to indicate that the production of the sound is due either 

 to a very slight leak from the exploder to earth — the machine 

 was inclosed in a wooden box standing on a wooden table^-or, 

 not impossibly, to the rapid variation of potential in the line. ' 



In the way above indicated it would appear to be possible to 

 transmit the Morse code by means of magneto -electric currents 

 under conditions which would render a battery absolutely inap- 

 plicable. George S. Clarke 



Cooper's Hill, April 17 : Herbert McLeod 



■^Poisonous Australian^Lake 



Perhaps some of your readers may be interested [in the 

 following : — 



This year the lakes forming the estuary of the Murray have 

 been very low and the water unusually Avarm. The river is very 

 low and the inflow to the lakes very slight and having a tem- 

 perature of 74° F. Lake Alexandrina— on calm days surface 



