NoVtMBEK 15, 1894J 



NA TUKE 



53 



cially connected, facts, it ceases to be a subject worthy 

 the serious attention of educated men. One turns to a 

 new book on elementary chemistry, hoping to find at 

 least an attempt to rescue chemistry from the overwhelm- 

 ing burden of so-called facts, beneath which the science 

 is in danger of being buried. In this case I confess to 

 disappointment. It may be replied that the chemistry 

 which is not clearly apparent in the purely descriptive 

 parts of the book is to be found in the " introductory out- 

 lines " wherein the " fundamental principles and theories " 

 of the science are stated. I admit at once that there is 

 much excellent matter in these earlier chapters ; but I do 

 not find there a connected setting forth of elementary prin- 

 ciples, as arising from facts, and binding facts into some 

 kind of harmonious whole. There is not much either 

 exact or imaginative treatment ; and these two I take to 

 be the notes of genuine science. 



The perusal of this book produces in one's mind a 

 strange feeling of inversion ; many things seem to be 

 standing on their heads. The reader feels that a rapid 

 mental rotation, to right or left, is demanded. Change is 

 very properly said to be the feature of all chemical occur- 

 rences ; but at a very early stage (p. 5), after two pages 

 have been occupied in lightly touching the subject of the 

 constitution of matter, the student is told that " Any 

 change which arises from an alteration in the structure 

 of the molecule is a chemical change." This is an 

 example of the topsy-turviness of parts of the book. 

 The statement quoted has a meaning when the meaning 

 of such a very symbolical expression as " structure of the 

 molecule " has been adequately grasped. At this stage 

 of progress the student cannot have any clear image 

 called up in his mind by the words I have quoted ; they 

 must be merely words to him. But he might have 

 grasped the prominent and characteristic features of 

 chemical change had these been put before him by well- 

 chosen experiments. Another instance, to my thinking 

 a glaring instance, of putting theory where facts should 

 come, and facts where theory, is found in chapter ii., 

 which deals with elements and compounds. The dis- 

 tinction between these classes of substances is stated at 

 once, and is stated only, in the language of atoms and 

 molecules. 



" In the substance sulphur, all the atoms composing 

 the molecules are alike ; while in water . . . there are 

 two distinct kinds of atoms in the molecule. Matter, 

 therefore, is divided into two classes, according as to 

 whether its molecules are composed of similar or of dis- 

 similar atoms. Molecules consisting of atoms of the 

 same kind are termed eteiitciitary violecuUs, and sub- 

 stances whose molecules are so constituted are known as 

 elements." 



The chapter which deals, and deals in a clear and 

 most praiseworthy style, with the laws of chemical com- 

 bination, is headed " The Atomic Theory." I think the 

 author must have taken his own words too literally 

 (p. 29) : 



" Dalton embraced the ancient doctrine of atoms, and 

 extended it into the scientific theory which is to-day 

 known as Dalton's atomic theory, and is accepted as a 

 fundamental creed by modern chemists." (The italics 

 are mine.) 



A " scientific theory " and a " fundamental creed " are 

 very different things. 



NO. 1307, VOL. 5 l] 



For his descriptive treatment of the materials from 

 which chemistry is built up, I think the author is to be 

 praised ; but I do not think he has succeeded in setting 

 forth the principles of the science of chemistry clearly, 

 adequately, or in fitting order. 



M. M. Pattison Muir. 



OUR BOOK SHELF. 



Astronomia Sferica. An Elementary Treatise. By 

 Francesco Porro. (Roma : Societ.'i Editrice Dante 



Alighieri, 1S94.) 



In these 160 pages, the author has endeavoured with 

 success to bring before his readers, in as simple a way 

 as is consistent with the subject, the elements of spherical 

 astronomy. With the exception of a small knowledge of 

 the rudiments of the differential calculus, the mathe- 

 matical ability is by no means taxed. The order in which 

 the subject-matter has been arranged, and the field 

 which is covered, can be gathered from the following short 



I summary. After dealing first with the sphere generally, 

 and the form and daily motion of the earth, the annual 

 motion round the sun, and the methods of the trans- 

 formation of coordinates, the measurement of time is 

 next explained, in which Kepler's equation, the equation 

 of time, and the transformation of mean into sidereal 

 time, and vice versa, are discussed. Then follows a 

 chapter in which the movements of the moon are clearly 

 expounded. 



Diurnal parallax and refraction, the variations of the 

 fundamental planes, aberration and annual parallax, form 

 the subjects for the next three chapters ; while the re- 

 maining ones are devoted to the determination of the 

 positions of stars and their proper motion, and to the solar 

 system in general. In the last-named, the apparent 

 movements of the planets, the theories of Copernicus and 

 Kepler, the necessary data for the determination of 

 planets' orbits, &c., are touched upon. 



From the above it will be seen that the most necessary 

 points for the student have been dealt with, but they 

 have not been treated at too great a length. As an in- 



I troduction to higher works, this book will be found most 

 useful ; but its use in this country will be to a great 

 extent restricted, owing to it being printed in Italian. 



The Nev Technical Educator. Vol. iv. (London, Paris, 



and Melbourne : Cassell and Co., 1S94.) 

 The previous volumes of this work have been duly 

 noted in our pages. Volume iv. is in every way up to 

 their standard of excellence. 



The subject of the manufacture of iron and steel 

 occupies the first part of the volume. The author of this 

 seems to be well acquainted with the practical details. 

 We note that he appears to consider that the presence 

 of but 005 per cent, of sulphur in steel is more or less 

 harmful, producing a metal sensibly red-short. This 

 may be the case ; but it is generally considered that the 

 percentages of phosphorus, sulphur, or silicon must 

 not each exceed 006 per cent., and then their efl'ects 

 may be overlooked in axles, tyres, plates, &c. Engine- 

 tyres are said to give a tensile test of 46 tons per square 

 inch, with a minimum elongation of 20 per cent, in a 

 3-inch length. These results are rather extreme, with a 

 sectional area of i square inch of test-piece. If the ex- 

 tension exceeds 16 per cent, the result maybe considered 

 good with this tonnage. 



As in previous volumes, we find much interesting 

 information on cutting tools, from the pen of Prof. R. H. 

 Smith, dealing principally with lathes, drills, and punch- 

 ing and shearing machinery. Different metal shavings 

 are illustrated from photographs, and clearly show the 

 nature of the different metals. The steel shavings shown, 



