966 



SCIENCE. 



[N. S. Vol. IV. No. 364. 



going into the detail of manipulation with 

 great care and thoroughness. 



In Chapter II., dealing with sources of elec- 

 tricity, somewhat more space than is necessary- 

 seems to be given to primary batteries, since in 

 this country at least such sources of current are 

 seldom if ever found desirable. The use of the 

 alternating-current supply is discouraged rather 

 briefly (p. 42) when we consider that a motor- 

 generator is known to be a very convenient and 

 efficient method of deriving a low-voltage direct 

 current from a higher- voltage alternating source. 



A very important point in the design of con- 

 tact breaks is emphatically presented (p. 66) 

 and exceedingly well explained. It is very de- 

 sirable that the duration of ' make ' be long as 

 compared with the time of 'break'; thus an 

 interval is allowed long enough for the current 

 to reach a maximum value before it is inter- 

 rupted. Makers quite often pay too little at- 

 tention to this, and writers frequently ignore it 

 altogether. 



The classification of breaks (p. 66) should, in 

 the writer's opinion, include a fifth, viz., me- 

 chanical breaks. Such breaks have been used 

 in this country with nauch success. 



In the description of various tubes (Chap. 5), 

 it is a cause of surprise and regret that one or 

 two very effective American tubes are not men- 

 tioned. The automatic regulating tube invented 

 by Sayen is used all over the United States and 

 has been highly spoken of abroad by no less 

 authorities than Lord Kelvin and^Rontgen him- 

 self. The scope and plan of the book in gen- 

 eral is such as to commend it to the writer as 

 the best of the few that have yet appeared on 

 the subject. 



It should be a very valuable aid to all en- 

 gaged in X-ray work who have not had much 

 experience of their own, though, as the author 

 clearly states, such personal experience is abso- 

 lutely necessary to all who would produce re- 

 liable results. 



Very little seems to be said in Mr. Eddyman's 

 book about the use of X-ray methods in medical 

 diagnosis, though that line has been considerably 

 developed in this country. The results of in- 

 vestigators in all countries except in England 

 seem to have been rather consistently over- 

 looked. Arthur W. Goodspeed. 



Lehrbuch der Meteorologie. Von Dr. Julius 

 Hann. Leipzig, Tauchnitz. 1901. Eoyal 

 8vo. Pp. xiv + 805. Pis. 8. Charts 15. 

 Figs. 111. 



That a text-book of meteorology from the 

 hand of the leading meteorologist of the world 

 would be a masterly presentation of the subject 

 was a foregone conclusion. No one is better 

 qualified than Dr. Hann to write such a book. 

 As director of the Hohe Warte in Vienna ; pro- 

 fessor in the Universities of Vienna and of 

 Graz ; editor of the Meteor ologische Zeitsschrift ; 

 a life-long original investigator of the widest 

 range of meteorological phenomena ; an earnest 

 student of meteorological publications in all 

 languages. Dr. Hann has brought to his latest 

 work a wonderfully rich experience and an 

 amazing fund of knowledge. 



The ' Lehrbuch der Meteorologie ' is more than 

 a text-book. It is rather a treatise on meteor- 

 ology. It ranks as a worthy companion to the 

 same au^thor's 'Handbuch der Klimatologie. ' 

 The * Lehrbuch ' is not intended to be a ' popular ' 

 presentation for beginners, nor is it adapted for 

 general reading. It is a systematic and concise 

 review of the whole subject of meteorology, as 

 complete as is possible within the limits of 800 

 pages. Nothing of any importance is omitted. 

 Admirable brief historical summaries of the dif- 

 ferent topics are followed by references to the 

 results of the most recent investigations. So 

 many, so well selected, and so complete are the 

 references, in text and footnotes, that the book 

 is indispensable to every student of meteorology 

 simply as a bibliography. In fact, teacher 

 and student alike will want to have this vol- 

 ume always close at hand, on their desk, or on 

 the nearest shelf of their bookcase. 



Since Schmid published his classical ' Lehrbuch 

 der Meteorologie,' in 1860, no author has at- 

 tempted so complete a presentation of the sub- 

 ject as has been given by Dr. Hann. In its 

 general plan the new ' Lehrbuch ' is not unlike 

 that of Schmid, allowing for the natural changes 

 which have resulted from the advance of the 

 science during the last forty years. Schmid' s 

 ' Lehrbuch ' was a landmark in its time, and is so 

 still, as a classic. Hann's ' Lehrbuch ' now occu- 

 pies, and will continue to occupy, a similar 

 position. Schmid' s book was overweighted 



