SCIENCE-GOSSIP. 



149 



Department. This has been attained thus : it will 

 have been noticed with regard to the sound-waves 

 in air that two objects may be made sympathetic 

 to a particular note. For instance, if a glass is so 

 sharply struck as to emit a definite sound, one of 

 the strings in a piano yards away will respond and 

 give off the same note. The reverse often happens, 

 when the performer on a piano is annoyed by some 

 object in the room responding when a particular 

 note is struck on the instrument. This fact has 

 been seized upon, and it is found that by " atuning " 

 for ether vibrations the transmitting instrument 

 and the receiver with great exactness, it is 

 possible to maintain the secrecy of wireless tele- 

 graphy as perfectly as can be done with a 

 "private wire" at the General Post Office. By per- 

 mission of Messrs. Seeley and Co., we reproduce 

 drawings from Mr. Kerr's book of a transmitting 

 apparatus and of a receiving apparatus used in 

 wireless telegraphy. With such simple instru- 

 ments messages have been sent through space 

 scores of miles. Nothing appears to disturb the 

 ether ripples which convey them, neither storm 

 nor obstruction, be it building or mountain. We 



legist's • orders ' are of far less morphological value, 

 while the time-honoured ' orders ' of Reptilia are of 

 infinitely greater importance. Each class has, so 

 to say, its own standard units, just as one nation 

 reckons in £ s. d., another with dollars and cents, 

 and a third with mark and pfennige, which again 

 are not the same as francs and centimes. How- 

 ever, to mitigate the discrepancies as much as 

 possible, and chiefly owing to the bewildering mass 

 of fossil reptiles which have come to light, I have 

 arranged the reptiles in numerous sub-classes, and 

 these again in orders, while for the host of fishes 

 ' divisions ' and ' legions ' have been resorted to as 

 intermediate groups between sub-classes and 

 orders. After all, the practical aim of our classi- 

 fications is sorting and grouping ; the ideal aim is 

 that the system should be a condensed expression 

 of the phylogeny of the creatures dealt with. 

 There are many, and there will be more classifica- 

 tions, all artificial and dependent upon the taxo- 

 nomic value which we happen to attribute to the 

 various organs. There can be only one true or 

 natural system, namely, that which expresses 

 every degree of affinity or descent of every 



Wireless Telegraphy — Receiving Apparatus. 



have already drawn deeply upon the information 

 contained in Mr. Kerr's work under notice, and it 

 would be manifestly unfair to exhaust his theme. 

 We have pleasure in strongly recommending this 

 book to our readers as an excellent account of a 

 little-understood subject. It is written in such 

 careful manner that there is not the slightest 

 difficulty in following the author's points. So 

 simple a story is it, as told by Mr. Kerr, that one 

 becomes fascinated, and finds, indeed, there is 

 something new in the world, and the news is of 

 immense importance to mankind in the future. 



A Classification of Vertebrata. By Hans Gadow, 

 M.A., Ph.D., F.R.S. 92 pp. SJ in. x 5J in. 

 (London : Adam and Charles Black, 1898.) 3s. 6d. 



In his new classification of the vertebrates, 

 Dr. Gadow includes both recent and extinct 

 animals. Perhaps the best way of giving our 

 readers an indication of the author's work is to 

 quote from his preface. He says: "The groups 

 into which we are used to combine the animals of 

 the various classes are not, and cannot be, all 

 equivalent. The least objectionable, or rather the 

 most generally accepted ' orders ' are those of the 

 Mammalia, and it is well understood that the ornitho- 



creature which has ever lived or is still living. 

 To that gigantic system, however, no classification 

 will be applicable. Each horizon will require its 

 own classification, with its necessarily arbitrary 

 boundaries." The arrangement is based upon 

 ascending order. With regard to nomenclature. 

 Dr. Gadow says: "Concerning generic names, I 

 have been as conservative as possible, using those 

 which we are familiar with in treatises of general 

 zoology and comparative anatomy." For this we 

 beg to offer the author our grateful thanks. The 

 index is most useful, and to a large extent also acts 

 as a glossary. This work is one that must be 

 studied by every zoologist with the slightest pre- 

 tence to scientific attainments. The book is 

 beautifully printed on alternate sides of the pages^ 

 leaving the others for the student's notes. 



A Text-Book of Zoology. By T. Jeffery 

 Parker, D.Sc, F.R.S. , and William A. Haswell, 

 M.A., D.Sc, F.R.S. 682 pp. 9jin. x 6 in., in two 

 vols., with 663 illustrations. (London : Macmillan 

 and Co., Ltd. New York: Macmillans. 1897.) 36s. 



The authors of this fine work are too well known 

 to require introduction, further than they were the 

 late Professor Jeffery Parker, of the University of 



