MINERALOGICAL SYSTEMS. • 2Q 



numbet of thofe parts ; it is the laft term of mineralogical Explanation of 

 analyfis. The primitive form, on the contrary, is its fi'ft re- ^^^^^'^^JJ^^^^^" 

 fiilt^ and retaining the exaft proportion of the component cryitals by the 

 parts, contains the greateji number of thofe parts. It is eafy "^'^thodof Hauy. 

 to fee that in the cafe above mentioned of the phofphate of 

 lime, the hexahedral prifra will be the primitive form, pre- 

 cifely for the reafons adduced to fhew that it is not the in- 

 tegrant particle. Though the Abbd does not decidedly de- 

 fine the integrant particle as containing the 7uinhimm of fpace 

 under the maximuin of furface, and the primitive form as con- , 



taining the maximum of fpace under the minimimi of furface,* 

 neverthelefs he makes a remark that authorifes the above de- 

 finitions (which. Sir, you will obferve are mine, lefl any fault 

 Jbe found with them.) He fays the dodecahedron with rhom^ 

 boidal fides, which is the primitive form of the garnet (grenat) 

 contains the maximum of fpace under the minimum of furface ; 

 and if it be cut into two equal and fimilar parts, it will prefent 

 the fame form as the bottom of the cell of the honey-comb, 

 which has the fimilar property. 



An objedion might be taken on the cuirre pyrileiiXf and the 



, cuivre gris, or the yellow and grey copper ore of Kirwan, the 

 Abb6 mentioning the regular tetrahedron as their primitive 

 form, and not the oftahedron as in other cafes. The reafon 



.may be, that all the cryfl;alline forms of their fubfiances which 

 he defcribes are (light modifications of the regular tetrahedron. 

 " The primitive forms hitherto obferved, fays the Abbe 

 Hauy, are reduced to fix. — The parallelipipedon, the .octa- 

 hedron, the tetrahedron, the regular hexahedral prifm, the 

 dodecahedron bounded by rhombs all equal and fimilar, and 

 the dodecahedron with triangular fides, formed by two right 



^pyramids united bafe to bafe." 



Healfo makes a diftindlion between integrant particles and 



fubjlra6iive particles ; thefe latter are always parallelipipedons, 

 I fliall fpeedily mention whence they derive their name. They 

 are fubftituted for the integrant particles, to facilitate .calcula-* 

 tions, and it is worthy of obfervation that the parallelipipedon 

 can always be obtained in all difledlions of cryflals. Thus far. 

 Sir, I have dated the firfi: principles of miner&logical analyfis ; 

 I fliall now proceed to the fynthefis. 



(To be continued.) 



* The Inclination of thg interfering planes being the fame. 



Dejcription 



