1818.] On Mr Darnell's Theory of Crystallization. 287 



Article IX. 



Observations on Mr. Darnell's Theory of Crystallization. By 

 Philo-chemicus Cantabrigiensis. 



(To the Editors of the Annals of Philosophy.) 



GENTLEMEN, Cambridge, March 8, 1818. 



Some apology may appear necessary for desiring to occupy a 

 page in the Annals by writing on a subject which two of your 

 correspondents have already discussed. The two gentlemen to 

 whom I allude have, through your journal, attacked Mr. Daniell's 

 paper on crystallization, published in the Journal of the Royal 

 institution for October last ; and as this paper (from the mode 

 of its publication) issues forth, under the sanction of the Royal 

 Institution, its influence, if incorrect, may justly be appre- 

 hended. 



To those who have preceded me I have but to observe, that in 

 their amusing papers they do not appear to have gone to the 

 bottom of the subject, and, therefore, have not detected all the 

 errors of the paper in question. 



If, as I trust, Mr. Daniell's object in a scientific investigation 

 is the furtherance of knowledge, he will examine a contrary 

 opinion with candour and attention ; if otherwise, he will learn 

 that genuine science will always outshine the ignis fatuus gleam 

 of empirical representation. 



With that which I shall not be misunderstood in calling the 

 Wollastonian part of the theory, I do not presume to interfere ; 

 but may take the liberty of transcribing a passage from Mr. 

 Daniell's paper,* and making some observations on the mathema- 

 tical theories there laid down. " The confirmation to which I 

 allude is founded upon the consideration of these circumstances, 

 fig. 11 and 12 represent a tetrahedral and octohedral pile of balls, 

 both composed of triangular faces, the bases of which are con- 

 stituted of four particles. The tetrahedron is contained by four 

 of these similar and equal planes, and the octohedron by eight ; 

 so that the whole superficies of the latter is exactly double that 

 of the former. Now it is obvious that solids so constructed 

 must differ in their specific gravities, unless the number of 

 elementary particles in the octohedron be exactly double the 

 number in the tetrahedron ; that is to say, unless the number of 

 atoms in a given space be equal in both arrangements. But it 

 will be found that the tetrahedron, f;g. 11, is composed of 20 

 spheres, and the octohedron, fig. 12, of 44 ; the latter containing 

 more than double the number of particles under a double surface. 



• Jour. Inst. Oct. p. 88. 



