448 Notices respecting New Books. 



tells me that he accepts this criticism. The labour of working- 

 out a fairly accurate analytical solution for any of Poincare's 

 looped orbits, by Hill's method, would probably be very 

 great. I have therefore thought it might interest others 

 besides ourselves to apply my graphic method to the drawing 

 of at least one of Poincare's looped orbits, in our Physical 

 (and Arithmetical) Laboratory in the University of Glasgow. 

 Figure 3 represents a looped orbit, which has been worked 

 out accordingly by Mr. Magnus Maclean, Chief Official 

 Assistant of the Professor of Natural Philosophy, from the 

 equations (14) (15) above. The initial values used for 

 obtaining the curve, were x=2; y = 0; fr = 10; 2E = — 130 ; 

 and .-. q 2 = S8'2 and p =4'8. 



LIII. Notices respecting New Boohs, 

 Organic Dyestuffs. 



Chemistry of the Organic Dyestuffs. By K. Nietzki, Ph.D. 

 Translated, ivith additions, by A. Collin, Ph.D., and W. Richard- 

 son. (London : Gurney & Jackson, 189^.) 



nPHE German editions of this little volume are so well known to ail 

 -*- chemists who interest themselves in the tar colouring-matters 

 that Messrs. Collin & Eichardson have done good service by pre- 

 senting Dr. Nietzki's work in an English form. The author, it is 

 perhaps needless to state, is Professor in the University of Basle, 

 and is best known in the chemical world as one of the most suc- 

 cessful investigators into the constitution of the complex organic 

 colouring-matters which science furnishes to technology. Coming 

 from the pen of such a recognized authority as Dr. Nietzki, no 

 special commendation is necessary to assure English students and 

 technologists that they have received a most important and valuable 

 contribution to their literature. The translators have done their 

 part of the work also with commendable skill, and have fairly well 

 expressed the author's meaning throughout. 



One special feature of the present work is its purely scientific 

 treatment of a subject which is necessarily intimately connected 

 with manufacturing processes. There are already in Germany 

 several exhaustive works on the technology of coal-tar colouring- 

 matters, notably those of Schultz and Muhlhauser, but while these 

 are replete with manufacturing details and reprints of bulky patent 

 specifications, Dr. Nietzki concerns himself more especially with 

 the classification and constitution of the compounds, and his work 

 appeals therefore to the purely scientific chemist as well as to the 

 technologist. Only sufficient technology is introduced to make 

 the scientific discussion coherent and intelligible. Many of the 



