JuN-E 1, 1888.] 



KNOWLEDGE ♦ 



IS^ 



to find anything of the sort. It appears, however, that ilr. 

 Fraser thinks I must have been satisfied with his theory, 

 but am prevented from saying as much by some mistaken 

 notion about the way in which the editor of Ivxowledge 

 should back friends who had written in these columns, even 

 though he judged them to be wholly in error. So he writes 

 to a gentleman whom he supposes, quite erroneously, to 

 have been acting editor of Knowledge as well as author of 

 the notice of his pamphlet, in terms implying that he has 

 been most unfairly treated. 



* * * 



Xosv all this is in exceedingly bad taste — to put the 

 matter very mildly indeed. If my friend had been both 

 author of the notice and acting editor of Knowledge, it 

 would have lieen quite improper to address him personally 

 about a notice which he had written in discharge of duties 

 ■which belonged to the position he occupied. (To appeal to 

 me, as Mr. Fraser had done earlier, was still worse ; but, as 

 I had heard the appeal, and had indicated my opinion, to 

 renew the charge of unfairness was doubly insulting — 

 insulting alike to me and to my friend.) 



* * * 



If paradoxists choose to send their lucubrations to 



Knowledge, they must accept the opinions expressed 

 here about them a-s decisive so far as Knowledge is 

 concerned. They are free to go about denouncing Know- 

 ledge as incompetent or unjust. If they can make their 

 theories acceptable to the scientific world, their abuse of 

 Knowledge will very likely be accepted along with those 

 theories. But they have no right to send their abuse to us 

 as well as their paradoxical pamphlets, or to complain 

 because we have given the opinion they have shown them- 

 selves anxious to obtain. 



* * * 



I do not feel bound to repeat or explain my opinion or 

 the opinion of my friend who noticed !Mr. Fraser's pamphlet. 

 But as it seems he is not satisfied that I really think his 

 theory unsound, and as he evidently believes I have not 

 noticed the arguments by which he considers he has met 

 objections, I may as well tell him that 1 do and have. He 

 regards " heat ' as the cause of gravity, and cannot see that 

 what we know about the nature and rate of transmission of 

 heat is entirely inconsistent with what we know about the 

 nature and especially about the rate of transmission of 

 gravity. He makes a wild yet feeble attempt to show how 

 heat would act tln-owjh the planets and suns, coming out on 

 the other side ; and he supposes he has made it clear that 

 the influences (purely imaginarj-) which he attributes to 

 heat-waves would be proportional to the masses, not to the 

 surfaces of bodies producing them ; but the proof does not 

 merit serious disproof. He has an idea that the great 

 dLfficulty about gi-avity resides in the shortness of the time 

 occupied in traversing the distances between the heavenly 

 bodies, so he triumphantly points out that no time at all 

 would be required by his bombarding waves to reach the 

 bodies acted upon, since they are travelling about all the 

 time. The question is not one of time, however, but of 

 velocity. It takes no time for a person travelling along in 

 a rain storm to receive the rain which he encounters at the 

 moment of his arrival at any place ; yet his velocity combines 

 with the velocity of the falling rain to aiTect the apparent 

 direction in which the rain falls on him. What we knoio 

 about gravity is that the velocity of its transmission almost 

 infinitely exceeds the velocity with which the planets travel, 

 and is many times greater than the velocity of light and 

 heat. 



The Geological History of Plants. By Sir J. W. Dawson. 

 (Kegan Paul, Trench, k Co.) — This is a valuable addition 

 to the International Scientific Series. An introductory 

 chapter is fitly occupied with the general facts of geological 

 chronology and the classification of plants, while the body 

 of the work supplies in convenient compass a summarj' of 

 the development of the successive floras, the typical vegeta- 

 tion of each period being admirably illustrated. AVe may 

 direct special attention to those portions of the seventh and 

 eighth chapters which, in treating of plant origin and 

 migrations, discuss the interesting question of the appear- 

 ance of specific types in Arctic latitudes, " the full sig- 

 nificance of which," Sir William Dawson remarks, " seems 

 only recently to have dawned on the minds of geologists." 

 Sir William might have added that the paramount import- 

 ance of the study of plants, as contrasted with that of 

 animals, in organic evolution, " seems only recently to have 

 dawned " on biologists. 



A Course of Lectures on Electricity. By George Forbes, 

 M.A., F.R.S., <tc. (London : Longmans, Green, it Co. 

 1888.) — This admirable series of lectures is based upon the 

 notes of five which were delivered by lilr. Forbes before 

 the Society of Arts in 188G, while the si.Kth (on Dynamo- 

 Electric Machinery) is a reprint of a paper read at the 

 Electrical Exhibition at Philadelphia in 1884. As a trust- 

 worthy introduction to electrical science, as developed 

 experimentally by Faraday, and subsequently mathematically 

 by Clerk Maxwell, it would be hard to surpass. Plain and 

 popular in language, but throughout scientifically accurate, 

 the fairly well-educated reader who gains his first intro- 

 duction to electricity through its pages will find, after an 

 attentive perusal of them, that he has acquired a sound 

 knowledge, not only of the principles of the science, but also 

 of the manner in which it is practically applied in electric 

 lighting, the telegraph, the telephone, and in the arts gene- 

 rally. No sounder and better rudimentary treatise on the 

 subject of which it treats has, so far, appeared. Seventeen 

 well-executed woodcuts supply all that is needed in the shape 

 of illustration. 



A Student's Manual of Psychology. By Friedeich 

 KiRCHNER. Adapted by E. B. Drought. (London: Swan 

 Sonnenschein, Lowrey, it Co. 1888.) — Wading painfully 

 through this volume, we are amazed that its author can 

 have contrived to render a subject so replete with interest 

 as psychology so horribly dull and wearisome. To read it 

 after perusing such works as Bain's '• The Senses and the 

 Intellect" and ''The Emotions and the Will," or Car- 

 penter's " Mental Physiolog}'," is like turning from an essay 

 by Elia to " Drelincourt on Death " or Hervey's " Medita- 

 tions among the Tombs." This is the more regrettable 

 as the author's obvious erudition is supplemented by that 

 thorough plodding painstaking so essentially characteristic 

 of the German scholar. A large part of the dissertation 

 " On the Nature of the Soul " seems to us the veriest 

 logomachy. 



The Playgrouiul of Science. By Johnston Stephen. 

 (London : 'Truelove & Shirley.) — Every student of physics 

 knows how much more he learns from experiments actually 

 performed by himself than from any amount of mere read- 

 ing. Acting on this admitted principle, Mr. Stephen, in 

 the capital little shilling's worth before us, gives plain 

 directions for the performance of sixty-nine experiments, 

 illustrating the phenomena of sound, light, heat, electricity, 

 magnetism, pneumatics and hydraulics, statics and dynamics, 

 with descriptions of the mode of consti-ucting the extremel}' 

 simple apparatus needed for their demonstration. All of 



