546 Notices respecting New Boohs. 



the final chapter (xv.) on the Invariant Theory of Conies, a sub- 

 ject previously lightly touched in 15 pages, now extended to 60 

 pages. We know of no text-book, in English, in which so many 

 developments of this branch are given. Our statement at the 

 beginning of this notice is, we believe, fully justified by this bald 

 sketch of the contents, when it is borne in mind that the proofs 

 are all that one could desire, and that the principles are fully 

 illustrated by a copious and excellent collection of exercises. The 

 specially numbered results, for reference, have grown from 641 

 to 1085. 



There is a large printed list of errata, but to this should be 

 added at least ninety more which we have come across ; and why, 

 in an English text-book, should we repeatedly meet with such 

 forms as " orthique," " orthologique," " synietrique "? For " anti- 

 polar" in many places "autopolar" should be read: in a few 

 instances this slip is indicated in the Errata. Again, there is the 

 uncertainty of the firsu edition in the spelling of proper names, 

 Simpson and Simson, Coates' and Cotes,' Appolonian and Apol- 

 lonian, de Jonquiers and de Jonquieres, where in each case 

 the latter is the proper form. All the above errata are easily 

 corrected by the reader, but we dwell upon them because the proof- 

 sheets passed through three or four hands at least. More im- 

 portant are the followiug slips : — On p. 7, line 6, insert — before 

 w'—x"; on p. 299, line 8, insert | after the — ; on p. 425, line 1, 

 for Brocard read Neuberg. "We do not think that the figures of 

 the conic sections are anywhere discussed : of course by tracing it 

 is readily seen that they are as drawn in the text. In the next 

 edition, which we hope will be soon called for, a few such state- 

 ments as "subject matter are," "become infinity large," and the 

 definitions of the conies (see pp. 173, 201, compared with p. 250), 

 should be amended. The figures which accompany the text, as 

 well as the type, leave little to be desired. The utility of the 

 work is greatly enhanced by an excellent index. 



Practical Chemical Physics (Physikalisch-chemische Methoden). 

 By Dr. J. Traube. Hamburg : Leopold Voss, 1893. 



The great modern development of organic physical chemistry is 

 mainly due to three important discoveries. These are (1) that organic 

 compounds can be arranged in series ascending by increments of 

 CH 2 ; (2) that for each increment there is generally a corresponding 

 equal change in physical properties ; and (3) that bodies of the 

 same molecular composition have often very different physical 

 character:, even when their chemical properties are nearly identical. 

 It fo^ows that a chemist wishing to obta'n a complete knowledge 

 of new compounds must study their physical properties, and the 

 volume before us has been written to satisfy the needs of such 

 srekers after knowledge. It does not trouble them with physical 

 theories but describes in plain (German) language the apparatus 



