KN()\vi,i.i)r,i:. 



Makcii. 191-'. 



variety as rc'},Mrds (itnsity. mass, depth i)f ciicoiiiitir, 

 anil all tlie other circumstances we have studied in 

 these articles, continually present us with rotarv 

 masses of dense teases, from wiiich selective molecular 

 escape has removcil the li},'ht f,'ases. Such rotarv 

 lU'lnilae tend always to hecome at a certain sta^e 

 meteoric swarms. A coujile of minor planets f^razinj,' 

 would ine\itahl\ |)roduce a meteoric swarm. The 

 ends of the spindle of the third hody of collidinj,' 

 suns we have deduced would be larf^ely iron, and 

 would tend to segregate into a number of such 

 associated groups of particles, gradually cooling to 

 larger and larger masses. It is a curious coincidence 

 how man\- of the more massive meteoric blocks are 



iron. The immense majoritv of impacts must !"■ 

 obliipie, aiul all grazing impacts must set up rfttation. 

 and the heavier elements left by atrimic sorting must 

 pass through the meteoric swarm stage. Hence 

 there is no cause to wonder at the number of comets, 

 nor that space should be rich enough in jiartides to 

 be lit up when electrical disturbances tend to rend«-r 

 cosmic dust luminous. The whole subject of comets, 

 their chiiracter and origin, their gorgeous magnih- 

 cence, the beauty of their ignited meteoric trains, is 

 full of wonder and interest : and this is my excuse 

 for submitting these dynamical deductions as offering 

 suggestions that may be used as tentative e.\])lanations 

 of their origin and character. 



RHX'IEWS. 



MICKOSCOPV. 



Moih-nt Microscopy. — By M.I. Cross and Martin J.Colk. 



J25 p;if;es. 113 illustrations. 83-in. X5i-in. 



(B.aillicre. Tindall & Cox. Price, 6/- net.) 



The fourth edition of this excellent treatise has now been 

 reached and forms a handbook of considerable value to the 

 amateur microscopist. It would not be difficult to criticise 

 such a work because of its omissions, but such criticism would 

 be obviously unfair. The ground that it attempts to cover is 

 so large, ranging as it does from the use and manipulation of 

 the microscope to the mounting and preparing of objects of 

 widely varying descriptions, that omissions are inevitable; but 

 enough is said in each case to enable a beginner to appreciate 

 the principles involved. 



Reference can then be made to larger and more specialized 

 works with a feeling of confidence that the knowledge already 

 acquired may be regarded as sound, and that it will serve as 

 a good foundation. 



The first four chapters, forming Part I of the book, are 

 devoted to the microscope and accessories, and sufficiently 

 practical instructions are given to enable a student to start 

 work on proper lines. 



It is interesting to see that the concluson is reached that 

 an English microscope is .still to be preferred to a Continental 

 one, when really serious and critical work is intended, a con- 

 clusion that is in agreement with the opinion of the majority 

 of serious workers in this country. Part II, consisting of 

 Chapters VI to XX, is devoted to methods of preparing, stain- 

 ing, hardening and mounting microscopic objects of all 

 descriptions, and embodies practically all the well-known 

 processes in each branch. 



Simplicity is the key-note all through, and it is dilficult to 

 imagine in what way the subject could be better dealt with, at 

 least considering the limitations imposed. The instructions 

 given are essentially of a practical nature, and the expressed 

 intention is to avoid the use of needlessly expensive appliances. 



Part III consists of a series of articles by well-known 

 workers in the particular branch in which each one specializes. 

 The subjects are dealt with, as might be expected, in a 

 masterly manner, but the Chapter XXI. by Mr. Cheshire, on 

 the Petrological Microscope, is particularly interesting. The 



polariscope is to the amateur a most fascinating adjunct to a 

 microscope, because of the beautiful effects that are to be 

 observed with comparative ease, but it is almost astonishing 

 to notice that in a great number of cases the user has no idea 

 of the elementary principles involved. Mr. Cheshire has 

 written a simple and lucid explanation of the subject that 

 cannot fail to be of exceptional service, and that has the 

 particular merit of giving a concrete notion of what really takes 

 place when light is polarized. In general, the book is so 

 evidently the work of earnest workers, that it may with con- 

 fidence be commended as a safe guide for those entering on 

 any field of work that involves the use of the microscope. 



J. i:. B. 



PSYCHOLOGY. 

 Iiifrixltiction to Psycliolo<iy. — By Robert M. Ykrkes. 

 4i 7 pages. 12 illustrations. 8-in. X5|-in. 

 (G. Bell & Sons. Price 6/6 net.) 

 Professor Yerkes is well-known for his careful and critical 

 work in comparative psychology. He here provides an out- 

 line sketch which is intended primarily to give students a 

 general view of the .subject-matter, aims, methods, values and 

 relations of the science of psychology. The book is carefully 

 planned ; enough detail is given to make the outline sketch a 

 picture, but not so much as to hide the unity of plan ; 

 psychological methods of generalisation and explanation are 

 brought into relation with the methods employed in other 

 branches of science ; class exercises involving experimental 

 work and introspection are provided ; and throughout the 

 specific psychological aim is kept in view. Especially praise- 

 worthy is the insistence on the fact that psychology is a 

 science in the making. The student is helped to realise that 

 correlations can only be established gradually step by step ; 

 that the complex concatenations of the mental life are often 

 such as at present defy analysis ; and yet that what has 

 already been accomplished affords ample promise of further 

 success on lines which are strictly scientific. The last part of 

 the six into which the work is divided deals with the practical 

 problem of the aid given by psychology to the control of the 

 mental life, and touches on eugenics and education. 



C. LI. M. 



NOTICES. 



BIRKBECK COLLEGE.— The Governors, Staff and 

 Students ot the Birkbeck College are uniting to present 

 Mr. James C. N. White, Chairman of the Governing Body, 

 with his portrait, painted by Mr. Seymour Lucas, R.A., to 

 mark the completion of fifty years' connection with the College. 

 The Secretary of the College would be glad to send particulars 

 to anyone desirous of taking part. 



MICROSCOPY.— Dr. Charles E. Gabell, Analyst to the 

 Iowa State Food Commission, has written a book of which the 

 first part deals with microscopy and the second with the 



microjcopical examination of drugs. It can be used in 

 connection with any biological work, but is intended more 

 particularly for the use of pharmaceutical and medical students. 

 SPECTROSCOPES.— We have received a leaflet from 

 Messrs. .A-daiu Hilger. Limited, which describes spectroscopes 

 and etalons. The first of the latter is a glass interference 

 form for use with the direct vision pocket spectroscope, show- 

 ing the Fabry and Perot ring system. The second, which 

 bears the name Fabry- Perot etalon, can be used with any 

 spectroscope. 



