Mr Haidinger on the Sei'ks of Cry sialluattoniyf' Apatite, 153 
If, in these formulae instead of w, we substitute the value 
of w! becomes 3, and mce versa ; so that, in fact, the two num- 
bers of derivation | and 3 will yield twelve-sided prisms, whose 
alternating angles are inversely equal to each other. 
The substitution of the number of derivation of the other 
pyramid, in these formulae, instead of m, would make m' = % 
Numerous very interesting results might still be obtained from 
a further continued comparison of the forms occurring in the 
crystals of apatite, and in those of other species which belong 
to the rhombohedral system. Among these I shall only men- 
tion, that the scalene six-sided pyramids, derived according to 
the numbers | and are far less generally to be met with in 
nature than those dependent upon the numbers 3and^. Yet they 
have already been observed in several species j for instance (P)J 
in rhombohedral quartz, being the pyramid noted ocr in Haiiy’s 
Figures, and in Figs. 3. and 4. of the present paper, (P)|, and 
(P -f- 1)1 in calcareous-spar, &c. whilst the peculiar character of 
the combinations of apatite, in as far as our present knowledge 
reaches, is quite unparalleled in the Rhombohedral System, in 
which it stands as isolated, and as remarkable as the series of 
crystallisation of rhombohedral quartz. 
There exists a striking analogy between the forms of Apatite 
in the rhombohedral, and those of Tungstate of Lime, (Pyra- 
midal Scheelium-baryte) in the pyramidal system. A more de- 
tailed examination of this analogy, how interesting soever it 
might prove, is a subject which requires so many particulars, 
that it will be better to defer it to some future occasion. 
Aet. XXIV. — Account (^‘ some remarlmhle and newly, dis- 
covered Properties of the Suboxide of Platina, the Oxide of 
the Sulphuret^ and the Metallic Powder of Platina. By Prof. 
Dobereinee of Jena^. 
]VJ[r Edmund Davy had shewn, in 1820, that sulphate of 
platina, if boiled in alcohol, and subsequently digested in am- 
• Translated and abridged from the original paper published in Gilbert’s An- 
nalefi der Phi/sifc, which Professor Gilbert has been so kind as to transmit to us 
previous to its publication in his valuable Journal.— -E d. 
