168 



KNOWLEDGE. 



[July 1, 1897. 



These magnitudes might be determined either by measure- 

 ment or by estimation. Captain Abney raised the important 

 question of controlling the chemical composition of sensi- 

 tive plates. Commercial photographic plates, he said, 

 might be divided into two extreme types: [a] those that 

 are sensitive to bright stats, but require a relatively long 

 exposure to bring out the fainter ones; and (b) those which 

 are comparatively more sensitive to the weaker rays than 

 to the stronger ones. Captain Abney proposed to control 

 the varying sensitiveness of these plates to the fainter 

 stars by imprinting on each film at the same time as the 

 reseau a scale of opacities, and which he himself proposed 

 to construct. Other minor 

 questions were also discussed 

 as to the reduction and 

 reproduction of plates and 

 measures, and the conference 

 proposed at their next reunicn 

 to entertain measures for 

 coming to the aid of those 

 observatories which find them- 

 selves unable to accomplish 

 their share of the catalogue 

 or chart series. 



The project for the erection 

 of a statue to Darwin in his 

 native town first took shape 

 in 1894, when Mr. Montford, 

 who is a native of Shrews- 

 bury, placed a sketch model 

 before his fellow to-n-nsmen. 

 But it was not until the end 

 of last year that the generous 

 offer of the Shropshire Hor- 

 ticultural Society to defray 

 the whole of the cost ren- 

 dered the project a practical 

 one. And, even then, the 

 onerous condition was made 

 that the statue should be 

 finished early in August, 

 leaving the artist only some 

 seven months for the execu- 

 tion of the work. The statue 

 is in bronze, and is erected on 

 a granite pedestal ; the site 

 chosen is the entrance gate- 

 way to the Public Library, 

 formerly the celebrated 

 Shrewsbury School, at which 

 Darwin received part of his 

 education. The work has 

 been viewed by many of 

 Darwin's friends, notably 

 Sir Joseph Hooker and Mr. 

 Francis Galton. Lord and 



Lady Farrer were particularly pleased with the portrait. 

 We learn that Prof. Francis Darwin and other members 

 of the Darwin family lent the sculptor their aid during 

 the progress of the work. 



CHARLES DARWIN. 

 The Xew Statue of Daewis by Mr. Horace Moxtfobd. 



To be erected in Slirewsbury, and unveiled on August lOtli, 1897, by 

 Lord Kexyox, President of the Shropshire Horticultural Society. 



Noti»s of Booits. 



The Aeronautical Annual, 1897. (Clarke & Co., Boston, 

 Mass., U.S.A.) This is the third, and certainly the most 

 interesting, of Mr. Means' annuals. Of course, the clief 

 il'ceinie is the description of Prof. Langley's world- 

 renowned success in driving an aiirial steamer through 



the air, thus demonstrating beyond dispute that the air 

 maybe navigated by steam, not only without the expedient 

 of gas displacement, but treating that old idea with the 

 contempt it deserves, of which Dr. Wolfert's experiment 

 is the latest illustration. Our readers are aware that Mr. 

 Hargrave, of Australia, is the inventor of the cellular kite, 

 and our cousins in the United States have taken up and 

 elaborated the idea, Mr. Chanute being well to the fore in 

 this work. From this side of the art will emanate the 

 best form of gliding or soaring apparatus, Prof. Langley's 

 success supplying what may be called the other side ; and, 

 when both have met together, as the result of further 



experiments, we shall have the 

 aerial steamer, independent 

 of gas bags, and providing 

 the swiftest, safest, and most 

 agreeable mode of travel. 



ElfCtro-rht/swloi/y. By W. 

 Biedermann. Translated 

 by F. A. Webby. Vol. L 

 (London : Macmillan & Co. 

 1897.) All students of phy- 

 siology will welcome Prof. 

 Biedermann's book as one of 

 the most valuable additions to 

 the literature of this important 

 branch of science. There are 

 few men more qualified than 

 the author to undertake awork 

 of this character, and we are 

 pleased to find that he has not 

 only given details of those con- 

 tributions to the subject which 

 heis generallyassociatedwith, 

 but has endeavoured — and, in 

 our opinion, successfully — to 

 cover the whole scope of our 

 present knowledge of electro- 

 physiology. The work has 

 grown out of the course of 

 lectures which Prof. Bieder- 

 mann has been giving for some 

 years past at the University 

 of Jena, and which have 

 attracted students from all 

 parts of the world. We feel 

 sure that the work before us 

 is destined to become the 

 standard text-book in electro- 

 physiology for many years 

 to come. The well-kaown 

 original researches of the 

 author, which have for so 

 many years past been amongst 

 the most valuable contribu- 

 tions to the ]\'ie7tcr Sit::u)ifis- 

 herkhu, are now condensed 

 and summarized and rendered more accessible to English 

 students. The book has the additional merit of containing 

 a very extensive bibliography. The illustrations are not the 

 least important featiu-e of the work, and considerable credit 

 is due to the translator for the lucid and comprehensive 

 manner in which he has reproduced Prof. Biedermann's 

 work to English and American students. 



Allermitinii Currents and Alternotimj Current Machinery. 

 By Prof. Dugald C. Jackson, C.E., and Prof. John Price 

 Jackson, M.E. (The Macmillan Company, New York.) 

 Illustrated. 14s. Books for students of electrical engi- 

 neering are often too full of specifications and illustrations 



