302 Notices respecting New Books. 



it appears white and resplendent. On the non-crystallized or 

 imperfectly crystallized surface of the iodine, which being in 

 a measure powdery and oflTering no determinate angle of re- 

 flection to the eye, the mercurial vapour adheres, but in no 

 flat surface or continuous determinate angle capable of re- 

 flecting a mass of light; it may be said it is here unpolished. 



Again, may not the angle under which it is necessary to 

 view a Daguerreotype picture be that of the facet of the iodic 

 crystal, and this be a further confirmation of my theory ? The 

 mercurial vapour covers the whole of the iodine, and thus 

 protects it from the further action of light. 



Such are the crude views I have formed on this subject, and 

 I trust they may lead to a further elucidation. 

 I am, Gentlemen, yours, &c. 



London, March 19, 1841. Martyn J. RoBERTS. 



LII. Notices respecti?ig New Books. 

 A System of Crystallography . By John Joseph Griffin. Glasg. 1841. 



WE have been favoured with a copy of a work bearing the above 

 title,but which might better have been called "A description of 

 120 porcelain models of crystals, according to a method newly in- 

 vented by the author"; for, with regard to Crystallography, we might, 

 on first turning over the uncut leaves, and meeting with zenith and 

 nadir of crystals, and north-east, north-west, and other meridians, 

 have supposed that the object of the book was to create a laugh 

 at the expense of the cultivators of that science ; but recollecting the 

 cost of publishing a rather bulky octavo volume, we felt compelled 

 to suppose the author serious, and we accordingly began at the 

 preface to separate some of the leaves. 



The first line of the treatise defines crystallography to be " the art 

 of describing crystals." But this, according to our notions on the 

 subject, is only one, and not the most important of its objects. We 

 have been accustomed to regard crystallography as a science of a 

 much higher order, by which the mineralogist is enabled, from a 

 fragment of a crystal, to discover its relation to some simple type 

 by which he may connect It with the species of mineral to which it 

 belongs. 



This view of the subject, however, does not appear from the above 

 definition to have entered into Mr. Griffin's contemplation, and his 

 system therefore, even if it possessed the merit he ascribes to it, would 

 render no additional service to mineralogy. 



We cannot afford either time or space for even a brief analysis of 

 the author's method, nor do we conceive that we should much be- 

 nefit our readers by giving it ; we shall therefore limit ourselves 

 to a few extracts and remarks. 



The preface begins thus : " There are many systems of crystal- 

 lography in print, but none in general use," a fate from which we 



