30 



KNOWLEDGE. 



January, 1915. 



way of talking or grumbling to themselves in a low tone, 

 often for an hour or more, before they go to sleep. They 

 nest in hollow trees, and sometimes peel the bark off the 

 branch below the nesting-hole. Lucas and Le Souef speak 

 of this as general, but Froggatt found it only in a few. 

 The bark was stripped off an area about a foot wide and 

 two feet long, just below the openings. The branch was 

 never ringed all round. The bushmen say that the Galahs 

 do this to make the stem so smooth that the Monitor Lizards 

 cannot creep round to rob the nest. As these Lizards 

 are not plentiful in the scrub country \\here Froggatt made 

 his observations, it is possible that the habit falls into 

 abeyance when there is no need for it. 



EFFECT OF POSTPONED MOULT.— C. W. Beebe 

 [Zoologica, Vol. I, pp. 2,53-8, 1914) redescribes his important 

 experiments on the " Effect of a Postponed Moult upon the 

 Sequence of Plumage in certain Passerine Birds." In the 

 cock Scarlet Tanager (Piranga erylhromelas Vieillot) the 

 brilliant scarlet nuptial plumage gives place at the autumn 

 moult to an olive-green winter dress, and is reassumed at 

 the spring moult. The autumn moult is normally associated 

 with the thin and poor condition which follows the breeding 

 season ; but in these experiments tame birds which had not 

 bred were placed under observation at midsummer. The 



light was gradually cut off, and the food supply augmented : 

 the birds became quiet and inactive, and rapidly put on fat. 

 Under these conditions no autumn moult took place, and 

 it was therefore concluded that the condition of fatness 

 or tliinness of the bird's body influences the moult. The 

 striking fact was that the birds retained their nuptial moult 

 till the foIlo\\ing spring, and then, on being gradually 

 brought under normal conditions, moulted directly into their 

 new summer dress without any intervening green plumage. 

 " We have thus proof that the outward manifestation of 

 the sequence of plumage in these birds is not in any way 

 predestined through inheritance bringing about an uncliange- 

 able succession ... of scarlet green, scarlet green, year 

 after year." It is, however, supposed that, wliile the birds' 

 condition postponed the moult, the " pigmental changes in 

 the blood " took place as usual, but were not apparent 

 because there were no new feathers to be coloured ; one 

 Tanager wliich was exposed to a sudden temperature change 

 lost weight rapidly, and underwent a belated moult into the 

 green \\'inter plumage. In those which did not moult till 

 spring the green potentiality must ha\-e similarly existed, 

 but it was succeeded by the scarlet plumage without 

 ever finding expression. Bobolinks (Doltchonyx oryzivorus 

 Linnaeus) were also brought from one nuptial dress to 

 another without any intervening winter plumage. 



REVIEWS. 



CHEMISTRY. 



A First Book of Chemistry. — By W. A. Whitton, M.Sc. 

 150 pages. 74 illustrations. 7-in. x4|-in. 



(Macmillan & Co. Price 1/6.) 



This little book is arranged on an excellent plan, for each 

 chapter opens with a series of experiments, most of which 

 can be carried out by a young student, and then explains 

 in simple language the deductions to be drawn from the 

 experiments. Thus, from the very first, the beginner is 

 taught to test every statement, and to take nothing for 

 granted. The subjects include solution, combustion, tlie 

 principal common elements and their compounds, and the 

 laws of chemical combination. Some account is also given 

 of various manufacturing processes, involving the appli- 

 cation of cliemical reactions. The book is well illustrated 

 by drawings of apparatus and plant, and exercises are 

 appended to each chapter. It should not fail to make the 

 learner want to continue the studv of cliemistry. 



C. A. M. 



A Manual of Practical Physical Chemistry. — By T. W. Gray, 

 M.A., D.Sc. 211 pages. 61 illustrations. 7^-in. x 5-in. 



(Macmillan & Co. Price 4 /6.) 



Instruction in practical physical chemistry presents 

 many difliculties where young students are concerned, for 

 much of the work is tedious and difficult to compress within 

 the limits usually assigned to it in a school course. The 

 author is therefore to be congratulated upon his suggested 

 series of exercises, each of wliich can be finished within two 

 or three hours ; and for this reason this little liandbook 

 will be found almost as useful to teachers as to students. 

 The usual subjects, including molecular weight determin- 

 ations, vapour pressure, density, optical activity, and 

 electromotive force, are dealt with at length, the different 

 forms of apparatus being fully described and illustrated 

 with diagrams, while a series of tables of useful data and 

 logarithms is appended. 



Curiously, although reference is made to the melting- 

 points of organic compounds, no description is given of 

 the various methods of determining the constant, and of 

 the corrections to be apphed to obtain the true melting- 

 point. This is an omission that might with ad\'antage 

 be made good in the next edition. 



C. A. M. 



The Chemistry of the Radio-Elements. Part II, " The Radio- 

 Elements and the Periodic Law." — By F. Soddy', F.R.S. 

 46 pages. 1 1 diagrams. 9-in. x 6-in. 

 (Longmans, Green & Co. Price 2/- net.) 



In no branch of chemistry has progress been more rapid 

 and more striking than in its latest offspring, radio-chemistry. 

 It is barely three years since the subject was fully dealt 

 with in one of these " Monograplis on Inorganic and 

 Physical Chemistry," yet a continuation is needed to cover 

 the advances made since Part I was published. The theories 

 that were then put forward tentatively as to the genetic 

 relationship of the radio-elements and their position in the 

 periodic table are now supported by a mass of experimental 

 evidence, and much light has been thrown upon the laws 

 that govern the disintegration of one element into another. 

 An outline of each important discover^' has been given in 

 " Knowledge " at the time, but all who are interested in 

 the subject will be glad to have this lucid survey of the 

 whole ground. Some idea of the scope of the book may 

 be gathered from the section headings, wliich include : 

 The Nature of the End Products, The Origin of Actinium, 

 Neon and Metaneon, Nature of Isotopes, The Structure of 

 Atoms, The Nature of the Argon Gases. 



After discussing the atomic weight of lead and the 

 evidence pointing to the chemical identity of radium-D 

 and lead, the author alludes to the dream of the alchemists 

 in the following words : " It is of interest to note how nearly 

 science has approached to the solution of the problem of the 

 alchemists. If thallium could be made to expel an a-particle, 

 or mercurj' one a- and one /3-particle, the product would be 

 isotopic \rith gold. Though, of course, this is not yet 

 possible, there can be little doubt that success would 

 follow the application of sufficiently great electric potentials 

 of the order of some millions of volts. So far as can be seen, 

 all insulating media, even a perfect vacuum, fail at potentials 

 far short of this, conceivably by such disintegration of the 

 material of the electrodes." C. A. M. 



Chemical Calculations. — By H. W. Bausor, M.A. 136 pages. 



7-in. X 5-in. 



(W. B. Clive. Price 2/-.) 



In this little book the calculations which are inseparable 



from chemistry from its very beginnings are dealt with 



concisely, yet at sufficient length to make them clear to a 



young student. The subject matter is more elementary 



