398 = Shor) Method of expreffing © > 
opinion, fo as to approaciy néareft to the propofed end;. and 
he gives a fhort fketch of his method, which contains: ene 
fome new w obfervations’ ris . bo Rit 
IX. Account of a fimple Method of reprefenting the different 
Cryftalline Forms by very Jhort Signs, exprefjing the Laws 
of Decrement to which their’ Structure is fubjetted. By 
©. HAvy. From Journal des Mines, An. IV. No. 23. 
Tur different eryftals belonging to each mineral fub- 
ftance ate conne&ed with one identical primitive form, 
,which, in its turn, ferves to conne& them in common. An 
accurate knowledge of thefe mutual relations depends upon 
that of the laws to which their ftructure is fubjefted, and of 
which the effeét is to determine the number’and affortment 
of the planes arranged around the primitive form, in order 
to produce the fecondary forms. By'a neceffary confequence 
the naturalift, who is famihar with the progrefs of thefe 
laws, nceds often only to keep in his eye the primitive form, 
and an account of the decrements which its angles or edges 
undergo, to reprefent to himfelf the polyedron thence refult+ 
ing, and to fee, in fome meafure, in idea, the metamorphofis 
of the nucleus from which this polyedron originates, 
Thefe confiderations induced me to conceive the idea of 
converting into very concife language, analogous to that of 
algebraic analyfis, a definition of the different laws by which 
fecondary cryftals are determined; and thus to compofe'a 
kind of formule reprefentative of thefe cryitals.- To accom- 
plith this, it will be fuficient to diftinguith by letters the 
anoles and edges of the primitive form, and to acconapany 
thefe letters with figures pointing out the decrement which 
* Dr. Chladni is the avthor alfoof a Differtation on the Mafs of )Iron 
found by Profeffor Pallas in Siberia, and of {ome papers.on fireballs. See 
fuch 
Phil. Mag. vol. il. ps 1, 225, and 337. 
