XXXII SCIENCE PROGRESS. 



its value depending almost entirely upon the fact that it embodies the 

 results of actual observation, instead of being drawn up from herbarium 

 specimens, supplimented by the more or less imperfect notes of 

 collectors. 



With regard to numbers of genera and species, it contains very 

 little that is not in Hemsley's account of the Flora in the Botany of the 

 Challenger Expedition. But it embodies all that that contains, with 

 very much additional biological, local geographical, and historical 

 matter. It has the double advantage of being a consolidation of the 

 work of a botanist who had access to Bertero's types and all previously 

 existing literature, with that of a botanist whose investigations were 

 conducted in the field. The author draws largely on Hemsley for 

 synonymy and general geography, and is careful to cite his authority 

 in every instance. The enumeration is preceded by an account of the 

 geography and geology of the islands ; a somewhat detailed history of 

 their botanical exploration ; and a full and interesting bibliography ; and 

 it is followed by an analysis of the flora ; a description of the vegetable 

 formations ; catalogues of the insects and birds ; and an appendix on 

 the products of the animals, and the management and conservation of 

 the woods and plantations. Dr. Johow has reduced a number of doubt- 

 ful species, and in return he describes about half a dozen as new. Not- 

 able amongst the latter are Centanrodendvon draccsnoides and Dendroseris 

 gigantea. The former is remarkable in the tribe Cynarece for its aboreous 

 character, and the latter for its size — up to twenty feet high, among the 

 cichoriaceous arboreous Compositae. The total number of endemic 

 species of vascular plants resulting from Dr. Johow's elaboration is sixty- 

 nine as against seventy given by Hemsley; and these belong to fifty-two 

 genera, whereof twelve are endemic, and to thirty-two natural orders. 

 In addition, there are seventy-four indigenous but not endemic spe- 

 cies. Reference has been made in Science Progress ^ to the sandal- 

 wood tree of Juan Fernandez. Dr. Johow succeeded in finding one tree, 

 after weeks of fruitless searching. 



The beautifully executed plates, illustrating the scenery and character- 

 istic types of vegetation add greatly to the interest and value of the 

 book. 



The Theory of Sound. By Lord Rayleigh. Second edition, revised 

 and enlarged. 2 vols., 480 + xiv., and 504 + xvi. pp. London : 

 Macmillan & Co., 1894 and 1896. 



There are three works in the English language on Natural Philos- 

 ophy which occupy quite a unique position ; these are Maxwell's 

 Electricity and Magnetism, Kelvin and Tait's Natural Pliilosophy, and 

 the work under notice. For in every branch of physics which has so 

 far progressed as to be treated by the methods of the mathematician we 

 continually make use of the results and investigations contained in 



' I., p. 401. 



