LITERARY NOTICES. 



269 



amount of electricity belonging to the 

 monad atom be taken as a unit, then 

 that of the dyad atom is two, of the 

 triad atom, three, and so on. Hence, 

 then, thanks first to Faraday and now 

 to Helmholtz, chemists have now a new 

 and unlooked-for confirmation of one 

 of their most important doctrines from 

 the science of electricity." 



LITERARY NOTICES. 



Popular Lectures ok Scientific Subjects. 

 By H. Helmholtz. Translated by E. 

 Atkinson, Ph. D. Second Series. Xew 

 York : D. Appleton & Co. Pp. 265. 

 Price, 81.50. 



The first series of Helmholtz's lectures 

 met with the success which has induced Pro- 

 fessor Atkinson to translate an additional 

 volume of them. It is gratifying to know 

 that the translator feels himself justified in 

 this, as it shows a growing popular appreci- 

 ation of solid intellectual work in science. 

 The contents of this volume are considerably 

 varied, and represent the action of Helm- 

 holtz's mind upon widely different subjects. 

 The first paper is an in memoriam address 

 on Professor Gustave Magnus, who died in 



1869. The essay is not a mere biographical 

 notice or an ordinary eulogy, but is rather 

 an analysis of the character and the scien- 

 tific labors of Magnus in connection with the 

 state of knowled^re and circumstances of his 

 time, so that the paper becomes in some 

 respects an interesting portion of scientific 

 history. 



The second paper is " On the Origin and 

 Significance of Geometrical Axioms," and it 

 was a lecture delivered in Heidelberg in 



1870. This discussion is not child's play, 

 but many will be attracted to master it be- 

 cause it breaks into the field of speculation 

 with regard to the different dimensions of 

 space. 



Artists will be interested in the ab- 

 stracts of five lectures " On the Relation of 

 Optics to Painting," which were delivered in 

 Cologne, Berlin, and Bonn. After the intro- 

 ductory he takes up successively the subjects, 

 form, shade, color, and harmony of color. 

 His point of view is neither that of the 

 practical artist nor of the student of pict- 



ures and schools of painting, but it is that 

 of the physiological optician who is master 

 of a subject. He shows in various ways 

 how a knowledge of the mode of perception 

 of the organ of vision may be of importance 

 to the artist. 



Perhaps the most striking of all the pa- 

 pers is the lecture " On the Origin of the 

 Planetary System." So much is said about 

 the nebular hypothesis of Kant and La- 

 place in these evolutionary times, that many 

 will be glad to see the subject summed up 

 within a moderate compass, and by an au- 

 thoritative hand. No man is better prepared 

 by his broad scientific erudition and his 

 thorough mastery of mathematical and ex- 

 perimental physics than Professor Helm- 

 holtz to report on the present state of 

 knowledge regarding the origin of the plane- 

 tary system. But it was very far from the 

 author's intention to make a mere popular 

 statement of what former inquirers have 

 arrived at. As one of the founders of the 

 doctrine of the conservation of forces, he 

 may be said to have been an original con- 

 tributor to the nebular theory ; and he is 

 very pointed in his remarks on the grave 

 scientific significance of the inquiry. He 

 says, " Science is not only entitled, but is in- 

 deed beholden, to make such an investiga- 

 tion. For her it is a definite and important 

 question the question, namely, as to the 

 existence of limits to the validity of the 

 laws of nature, which rule all that now sur- 

 rounds us ; the question whether they have 

 always held in the past, and whether they 

 will always hold in the future ; or whether, 

 on the supposition of an everlasting uni- 

 formity of natural laws, our conclusions 

 from present circumstances as to the past, 

 and as to the future, imperatively lead to 

 an impossible state of things ; that is, to 

 the necessity of an infraction of natural 

 laws, of a beginning which could not have 

 been due to processes known to us. Hence, 

 to begin such an investigation as to the 

 possible or probable primeval history of our 

 present world, is considered as a question 

 of science no idle speculation, but a ques- 

 tion as to the limits of its methods, and as 

 to the extent to which existing laws are 

 valid." 



Professor Helmholtz is of opinion that 

 our planetary system must sooner or later 



