j536 Intelligence and Miscellaneous Articles. 



tion of more extensive subjects, and have consequently presented it 

 in a shape not so well adapted as it might be to the beginner. Of 

 course no one can attempt even to commence such a study "without 

 a previous familiarity with all the other branches of mathematics, 

 such as dynamics, dilFerential calculus, &c., necessary to its com- 

 prehension, and a knowledge of these is of course assumed by all 

 the writers on the lunar theory in a greater or less degree. But 

 supposing this preliminary knowledge in the reader, there yet remain 

 numerous difficulties peculiar to the lunar theory itself, and it is in 

 treating of these that the author of the work before us has shown 

 his aptitude and abilities as a teacher. To those who are not already 

 familiar with the science, it would be impossible to state what are 

 the peculiar merits of the work ; to those who are^ it will be suffi- 

 cient to say, that there are improvements introduced here and there 

 throughout the whole, and more especially in those parts where the 

 beginner is most likely to make mistakes. In particular we would 

 direct their attention to the sixth chapter on the " Physical Inter- 

 pretation" of the various terms in the equations, and to the last 

 chapter on " The History of the Problem before Newton," in both 

 of which the author shows himself greatly superior to very many 

 of the Cambridge mathematical book-makers (especially those of his 

 own college) who slur over the principles and real foundations and 

 difficulties of a subject, in order to hasten to the mere mechanical 

 part, requiring only algebraical dexterity. In short, Mr. Godfray's 

 ' Lunar Theory' is the work of a man who thoroughly understands 

 the subject himself, and possesses more than the usual ability to 

 convey his knowledge to others. As an elementary treatise and 

 introduction to the subject, we think it may justly claim to supersede 

 aU former ones, and we have little doubt that as such it will soon be 

 adopted as the text-book at Cambridge and elsewhere. 



LXXXIV. Intelligence and Miscellaneous Articles. 



ON A METHOD OF DISTINGUISHING THE VOLATILE OILS OF THE 

 SERIES C* h1 by C. OREVILLE WILLIAMS. 



To the Editors of the Philosophical Magazine and Journal. 



Laboratory, Oxford Court, 

 Gentlemen, April 25, 1853. 



THE fact has long been notorious, that we possess no strictly 

 chemical means of distinguishing the volatile oils of the series 

 C* H* from each other. The taste, smell, and the action of polarized 

 light have been hitherto the only distinctive character. Any facts 

 tending to throw a light, however small, on this branch of the 

 science, cannot, I think, be otherwise than acceptable. 



Schonbein tells us that certain of the oils, when ozonized, have 

 the power of converting the black sulphuret into the white sulphate 

 of lead ; but from some experiments which I had occasion to make - 

 some time back, I felt convinced that several of the oils possessed^^ 



