THE PROGRESSIVE 

 SCIENCE SERIES 



EACH volume is complete in itself, and deals with some 

 one subject which is treated, so far as is possible, in a 

 fashion suited to the non-expert reader ; but naturally 

 the more or less popular character of each volume of 

 the series varies with its subject-matter. The series is 

 not confined to the purely technical side of the various 

 sciences ; but social and- economic questions are con- 

 sidered from their scientific aspect. A feature of this 

 series of textbooks is the attempt which is made in 

 each volume to give not merely an up-to-date account 

 of the subject with which it deals, but also a forecast of 

 the future, with indications of the lines in which workers 

 are at present engaged in extending their knowledge 

 of the subject. In all cases where it is necessary or 

 useful the volumes are abundantly illustrated, and care 

 has been taken with the type, paper, and binding. Each 

 author writes upon that subject upon which he is more 

 specially entitled, by original research, to be heard ; the 

 names given below, as well as those of others who 

 have undertaken to contribute volumes, are a guarantee 

 of the thoroughness with which the several subjects 

 are treated. 



The GLOBE says : " So many books of popular science are published 

 at the present day which are not scie?itific at all that it is a relief to 

 welcome another volume of the excellent "Progressive Science Series " 

 issued by Mr. John Murray. They have all the moderation of state- 

 ment and fulness of detail which is essential ; the mere hypotheses and 

 cocksure theorising of what one may call the penny manual are 

 conspicuously absent. Yet the whole series is not dear, considering the 

 size and the amount of work contained in each book" 



LONDON 

 JOHN MURRAY, ALBEMARLE STREET, W. 



