September 21, 191 1] 



NATURE 



\77 



easier to grasp the conception of a creation which 

 took place at one single time than a creation which 

 continues throughout all ages. Indeed, if we come 

 to think of it, the continuance of a physical law like 

 that of gravitation is as much a miracle as the con- 

 tinuous uniform creation of matter would be." 



In this, as in a few other matters, the reviewer is 

 unable to follow him completely. 



Coming to another subject, the lecturer has 

 some wise things to say regarding laboratory teach- 

 ing in physics; some of which — like much else of 

 school teaching — is calculated rather to promote dis- 

 like and dulness than to arouse any enthusiasm for 

 science ; and whatever may be the merit of college 

 courses in physics, he cannot refrain from noticing 

 how little of that sort of training was available for, 

 or was needed by, the great discoverers. 



"The cardinal fact to bear in mind is that previous 

 to 1870, when laboratory instruction, if given at all, 

 was sporadic, the experimental skill of investigators 

 was as great as it is now. We need only mention the 

 names of Faraday, Joule, Helmholtz, and Regnault, 

 in support of that contention. The conclusion is 

 irresistible that an intelligent student, possessing a 

 sufficient theoretical knowledge, is capable of starting 

 research work in physics without previous special 

 training. It is not for him that complicated labora- 

 tory courses have been designed, but for the ordin.m 

 student." 



It is very desirable in all cases that the stimulation 

 of interest shall not be subordinate to the acquisition 

 of mere technical skill. Without enthusiasm, the 

 mere ability to measure all sorts of uninteresting 

 quantities is of comparatively little use. 



" The future investigator will no doubt ultimately 

 save time if at an early stage he acquires a certain 

 technical skill and becomes acquainted with physical 

 methods, but otherwise the efforts of the teacher 

 should be directed to stimulating his scientific activity 

 rather than sending him through all manipulations 

 which he might possibly have to perform." 



That the author is a great authority in the subjects 

 of terrestrial magnetism and atmospheric electricity 

 is well known, and in his last lecture he enters into 

 these rather fully, compared with his rapid survey of 

 other subjects. Hence these portions have a value of 

 their own, and a few obiter dicta may be extracted. 



Concerning the view which has been held about 

 the annual and diurnal variations in terrestrial mag- 

 netism, he says :— 



"A better agreement may be obtained bv making 

 the plausible hypothesis that the electric conductivity 

 of the higher regions of the atmosphere is due to 

 solar radiation, and is therefore greater in summer 

 than in winter, and also greater in daytime than at 

 night." 



On the subject of atmospheric electricity : — 

 "The earth as a whole is charged negatively, and 

 on the average we find that there must be nearly a 

 million electrons on every centimetre of its surface. 

 . . . Lenard, in an important research, has shown 

 that a drop of water as it falls never reaches a 

 velocity greater than S metres per second, however 

 large the drop, while drops having a diameter of i'5 

 millimetres fall with a velocity of about half that 

 amount. . . . The larger drops break up in the air, 

 and doing so become positively electrified, according 



NO. 2l86, VOL. 87] 



to Dr. Simpson. If the ascending current spreads 

 out laterally near the top of the cloud, the vertical 

 velocity is diminished, the drops will grow and fall, 

 but only to break up and be carried upwards again. 

 A quantity of electricity large enough to account for 

 the lightning discharge can thus accumulate in a 

 cloud." 



We have thus taken a rapid survey of this interest- 

 ing book and given a sample of its contents. 



The only fault we have to find with it is a minor 

 one, that ought not however to pass unnoticed, — the 

 punctuation is of a systematically irritating kind. In 

 the extracts here made it has in most places been 

 corrected, so that the defect will not be noticed in 

 them, but before concluding we must quote without 

 correcting. There is evidently some one among the 

 printers or readers for the press who has a theory 

 about commas ; one rule apparently being that a 

 comma must always precede a relative pronoun. 



To illustrate the nonsense which is often thus made, 

 it will suffice to quote a few sentences at random : — 



P. 158: "To put the result in a form, which is 

 readily appreciated, I will compare different mole- 

 cules," &c. 



P. 98: " Energy cannot be expressed entirely by 

 quantities, which merely depend on change of position 

 (kinematical factors), but must involve," &c. 



P. 139: "Nothing has been said as yet on the 

 explanation of the secular variation of terrestrial 

 magnetism, and in our ignorance of the causes, which 

 make the earth behave like a magnet, it is perhaps 

 wisest to put the question aside for the present." 



P. 130: "The discussion of the problem [of diurnal 

 variation of terrestrial magnetism] . . . shewed that 

 there is a substantial remnant which comes to us 

 from the inside of the earth, and this is, as it should 

 be, because the earth being a conductor, any change 

 of the magnetic forces must give rise to induced 

 internal currents." 



The main part of the cause of diurnal variation, 

 however, lies above the surface of the earth, and is 

 due to electric currents in the upper atmosphere, — says 

 the author; who thereby seems to contravene a more 

 general pronouncement, quoted above, as to the 

 uniqueness of a given explanation. It is probably the 

 more general pronouncement that he would wish to 

 modify. 



The immediately preceding extract is of interest for 

 its own sake, and not merely as an illustration of serio- 

 comic punctuation. So is the following : — 



P. 156 : " It is always satisfactory when we find 

 that different lines of reasoning lead to the same re- 

 sult, and at present there is hardly one, in the domain 

 of Geo-Physics which stands on so firm a basis as 

 that giving to the earth an extremely high rigidity." 



In the selected quotations we have done less than 

 justice to the author's treatment of the many problems 

 which have coincided with his active life, and to the 

 solution of which he has so often contributed ; but 

 the book is accessible and very readable. We may 

 be grateful to the University of Calcutta for having 

 stimulated the production of these lectures, and to the 

 author for writing them out and publishing them. 

 They constitute another link in the chain which is 

 binding together East and West. 



Oliver Lodge. 



