On the Re-agents of the Muriatic, &c. Acids. 17 



become progressively predominant, until it be, in its turn, 

 tile only colour perceived. The intcirmediale hues will be 

 different degrees of green, to which will succeed various de- 

 grees of blue before arriving at the violet shades : all this 

 may be easily conceived. 



Ifj ixoreover, the green substance is itself placed above a 

 red matter, the latter will not be visible in ihe intervals of 

 the coloured matters of the upper layers ; but if these coats 

 come to acquire transparency by the imbibition of a liquid, 

 in this case the influence of the undermost layer will be sen- 

 S'ble, and will necessarily manifest itself in this case by a 

 yellow or even a reddish colour, when viewed perpendicu- 

 larly, while the oblique reflections v^'ill give greenish and 

 violet-coloured hues. The drying of the substances will af- 

 terwards restore things to the first state of which we have 

 spoken. 



Such in reality are the variations of shades of certain 

 places of the feathers of a peacock. Such, in my opinion, 

 is the probable cause of their formation ; applicable also to 

 those of the cock, the pigeon, and several otner birds and 

 insects; and in particular to that magnificent butterfly with 

 large wings, which through their whole surface present a 

 brilliant green, converted gradually, by means of obliquity, 

 into a still more beautiful violet colour *. 



III. Upon Ihe most sensible Re-'age/its with respect to the 

 Muriatic, the Carlonic, the Sulphuric Acids, and Am- 

 monia. By M. Pfaff, Professor of Chcmistrj/ at Kiel\. 



In experiments upon the supposed formation of the mu^ 

 riatic acid in water by the influence of the Galvanic pile, it 

 is certainly of great importance to possess a re-agent of 

 great sensibility with reaped to the above acid, in order to 



=«• The author iiiijjlit nlso have drawn jr-fcrcnces illi:5t!qtive of his subjeot 

 from tho'.p silk and worsted stufFs which are woven with their v.cft and woof 

 of different colours. Thc!c always exhibit the on? or ilie other colour, ac- 

 cording to tiie angle sinder which their v.irface is viev.-cd. — L»;t. 



t From Av'wihs tie Cliimie, torn. Ixii. j). ly. 



Vol. ep. No. 113. Ocif, isor. B bte 



