August, 1903.] 



KNOWLEDGE 



185 



Sussex, on May 13th lust, and were exhibited by Mr. Riiskin ButterGeld. 

 This Wagtail, which is also known under the name of M. boreatis, 

 Sundev.,i8 much like M. /lava, but has the head blackish-i;rey instead 

 of ashy-blue. The Grey-lieaded Wagtail breeds in northern Europe 

 and Siberia, and migrates to South Africa and India. Two specimens 

 are said to have occurred at Penzance, but the above are the first 

 authenticated records of its occurrence in the Britisli Islands. 

 Judging by its distribution, one would have expected this Wagtail to 

 have occurred more often on our eastern seaboard. 



Black-headed Waylail CMulacilla felilegcti, MichahJ in Sussex. — 

 At the same time and place as the two Sussex specimens of M. 

 viridis were obtained, an adult male of M. feldegyi, Michah, or 

 M. melanocephala, Licht., was shot. Tliis Wagtail has a black head, 

 and is altogether a darker and more richly coloured bird than 

 M. viridis. It also winters in Africa and India, but its summer 

 haunts are in south-eastern Europe, Persia, and Central Asia, so that 

 it can never be regarded as anything more than a straggler to these 

 islands. 



All contributions to the column, either in the way of notes 

 or photograplts, should be forwarded to Harry P. Witherby, 

 at the OJice of Knowledge, 3'2<5, High Holhorn, London. 



j^oticts of ISoofts. 



"The Soil: An Introduction to tub Scientific Study 

 OF THE Growth of Crops." By A. D. Hall. Pp. xiii. and 

 286. (Murray.) Illustrated. 3s. Gd. — Agriculture iu England 

 is usually practice without science ; and agricultural soieuoe, on the 

 other hand, often neglects the results obtained by generations 

 of farmers in their fields. Mr. Hall, we are glad to notice, 

 recognises the value of the accumulated experience of the 

 farming community, yet he shows that the study of the soil as 

 a complicated laboratory in which chemical, physical and 

 biological agents are at work, is the only sure means by which 

 tillage operations can be improved. " But," he remarks, " it 

 must not be supposed that science is yet in a position to reform 

 the procedure of farming, or even to effect an immediate 

 increase in the productivity of the land ; agriculture is the 

 oldest and most widespread art the world has known, the appli- 

 cation of scientific method to it is very much an affair of the 

 day before yesterday." This is the opinion to which every 

 man of science who knows anything of farmers and farming is 

 bound to be led. Mr. Hall's book may only be read by a few 

 ])eople engaged in agriculture, but it is one which every student 

 in an agricultural college should be expected to buy. We know 

 of no volume in which the constitution and work of the soil are 

 dealt with so instructively, for though Warington's " Physical 

 Properties of Soil" is a standard treatise, its scope is not so 

 wide as that of the volume under notice. Mr. Hall is indeed 

 to be congratulated upon his book, which contains many 

 original observations, and is in other respects a noteworthy 

 addition to the literature of agricultural science. We miss, 

 however, reference to Schlichter's memoir on the motion of 

 underground waters, though it contains the results of important 

 investigations connected with sewage in soils. 



"Chemical Technology." Vol. IV. Edited by W. J. 

 Dibdin. " Electric Lighting," by A. G. Cooke. " Photometry," 

 by W. J. Dibdin. Pp. xviii. and ;{78. (J. & A. Churchill.) 

 Illustrated. 'iOs. — One hundred pages of this book deal with 

 photometry, and in the remainder the various systems, machinery, 

 lamps, iSic, in use for tlie supply of electric lighting are 

 descriljcd. The book is not intended for students of physics, 

 or for electrical engineers, but for architects, civil and 

 mechanical engineers, and other professional men who 

 wish to obtain a general idea of the practical side of 

 the subject. Principles are therefore not given so much atten- 

 tion as their applications. At the same time, sulHcient con- 

 sideration is given to scientific theory to enable an intelligent 

 view to bo obtained of the construction and working of electrical 

 machinery, the distribution of current, and the determination 

 of candle power. The conditions under which commercial work 

 is carried on differ from tho.se of the laboratory, and the fact 

 that Board of Trade regulations are introduced wherever they 

 bear upon the matter described helps to make the book of real 

 practical value. Of cour.so, it is impossible to obtain an intimate 

 acquaintance with dynamos, storage batteries, electric lamps, 

 photometers, and the like, without actually using them ; but 



anyone who has had the opportunity of studying electrical 

 plant of any kind should have no difficulty in understanding all 

 that the book contains. Photometry, as might be expected, is 

 very well treated, practically every instrnment of importance 

 being described. An appendix giving the " Metropolitan Gas 

 Referees' notification of method for testing the gas supplied 

 to London " is of special interest in connection with the com- 

 petition between gas and electric lighting. 



" Exi'ERiMENTS ON Animals." By Stephen Paget. Withan 

 Introduction by Lord Lister. Pp. xvi. and 387. (Murray.) 

 Price Gs. — This book should do a vast amount of good. In its 

 original form it contained many references to misleading com- 

 ments made by anti-vivisection societies, but these have been 

 omitted, and the book is now a calm statement of progress in 

 medical science, more particularly preventive medicine, from 

 Galen to the present day. Galen, who lived in the second 

 century, made many valuable observations by experiments on 

 animals, but the methods followed by him were not continued 

 by his successors, and though the knowledge of anatomy made' 

 progre.ss, physiology remained as Galen left it until the time of 

 Harvey's discovery of the circulation of the blood in IG'28. 

 After this came the discovery of the lacteals and of the whole 

 lymphatic system, exjierimental studies of the digestive pro- 

 cesses, the production of bone, and the physiology of the nervous 

 system. 'The first part of Mr. Paget's book is occupied with 

 the record of these advances. In the second part, experiments 

 in pathology, materia medica and therapeutics are described, 

 and the third part contains a reprint of the Act relating to 

 experiments on animals in Great Britain and Ireland. Modern 

 medical sciences may almost be said to be confined to the second 

 part. Here we have clear and convincing summaries of the 

 work of benefactors of the human race like Pasteur and Lister, 

 and readers who are not familiar with the progress of 

 preventive medicine during the last fifty years will when they 

 have learnt what has been done, bless the men whose work, 

 often carried on against bitter opposition, has enabled us to 

 fight disease intelligently. Consider what has been done to 

 ])revent and combat septiciemia, pyemia, anthrax, diphtheria, 

 rabies, malaria and yellow fever during the last fifty years, and 

 you will obtain a slight idea of the benefits which mankind has 

 received from experimental methods in medicine. Want of 

 knowledge of what has been done is responsible for much of 

 the opposition to the experiments by which the results have 

 been obtained. With Mr. Paget's clear and judicious state- 

 ment available, there should be no excuse for ignorance, and no 

 want of an answer to those who ask for evidence of the value 

 of experimental medicine. 



"Variation in Animals and Plants.'' By Dr. H. M. 

 Vernon. Pp. ix. and 415. (Kegan Paul.) Illustrated. 5s.— 

 Natural history is becoming a branch of mathematics, and what- 

 ever field naturalists may think of the development, there Kin 

 be no question of the substantial nature of the results obtained 

 in the new department of scientific inquiry. Francis Galton, 

 Karl Pearson, Weldon, and others, have laboriously counted, 

 weighed, and measured animals and plants of various kinds with 

 the view of discovering the character and cause of variation ; 

 and an energetic school of biologists — Dr. Vernon among them — 

 has been established in which their methods have been followed 

 with success. In the volume under notice, the jirinciples and 

 results of bio-metric investigations are brought together, and 

 their significance from the point of view of organic evolution is 

 discussed. As an instance of the nature of the material thus 

 studied. Prof. Bumpas's paper on the effect of storm on sparrows 

 may be mentioned. One hundred and thirty-six sparrows were 

 collected after a very severe storm of snow, rain, and sleet in 

 North America, and of these 72 revived, while 04 perished. 

 Measurements of each sparrow were made with the view of 

 determining differences in the characters between the eliminated 

 individuals and the survivors. The results showed clearly that 

 the birds which departed most from the normal ty])c were 

 destroyed by the process of natural selection. Summing up the 

 observations, Dr. Vernon remarks, " The ue.xt generation of 

 birds collected in the storm-swept area would accordingly be 

 shorter in length, weigh less, have longer legs, have a longer 

 sternum, and a greater brain capacity than the former generation ; 

 supposing, of coin-se, that the variations existing in these 

 charactors were partly of blastogenic, and not wholly of somato- 



