108 On some new analytical Researches 



and regularitv, such as the cube, the regular octahedron, 

 the dodecahedron with rhombous planes all equal and similar, 

 Inc. These forms are kinds of limits which crystallizatioa 

 attains by different routes; while, with respect to other 

 forms quite different from those liitiits, it has a single di- 

 rection only which ends in any particular species of mineral. 



Laivs to which the Structure is subjected. — After having 

 determined the primitive forms, and those of the integrant 

 molecules, it remains to inquire for the laws pursued by 

 these molecules in their arrangement, in order to produce 

 these regular kinds of envelopes,"which disguise one and the 

 same primitive form in so many different ways. 



Now observation shows that this surrounding matter is 

 an assemblage of laminae, which, setting out from the pri- 

 mitive form, decrease in extent, both on all sides at once, 

 and sometimes in certain particular parts only. This decre- 

 ment is effected by regular subtractions of one or more 

 rows of integrant molecules ; and the theory, in determining 

 the number of these rows by means of calculation, succeeds 

 in representing all the known results of crystallization, and 

 even anticipates future discoveries indicating forms which, 

 being still hypothetical only, may one day be presented to 

 the inquiries of the naturalist. 



Some very simple examples will serve for giving an idea 

 of the laws to which the decrements in question are sub- 

 jected. 



[To be continued.] 



XV. The Baktrian Lecture. An Account of some new analij' 

 tical Researches on the Nature of certain Bodies, particu- 

 larly the Alkalies, Phosphorus, Sulphur, Carbonaceous 

 JSIatter, and the Acids hitherto 7indecomposed : with soine 

 general Observations on Chemical Theory. By Hi'Mphry 

 Davy, Esq.y Sec. R.S., F.R.S. Edin., and M.R.I.A. 



[Continued from p. 19.] 



IV. Analytical Experiments on Phosphor us. 



JL HE same analogies apply to phosphorus as to sulphur, and 

 I have made a similar series of experiments on this inflam- 

 mable substance. 



Common electrical sparks, passed through phosphorus, 

 did not evolve from it any permanent gas ; but when it 

 was acted upon by tlie Voltaic electricity of the battery of 

 jfive hundred plates in the same manner as sulphur, gas was 

 produced in considerable quantities, and the phosphorus be- 

 came 



