52 
Mr, Warlngton on the coloured Mims 
of both systems and giving superior attention to the worst, if 
written previously; and if otherwise, why is no reference 
made to the treatise conducted with the common Roman no- 
tation? These considerations are almost sufficient of them- 
selves to throw a doubt on its genuineness, although we must 
wait for the discovery of more direct evidence before any de- 
finite conclusion is broached. I know not what the forth- 
coming work of M. Chasles may contain, but every one in- 
terested in these matters must be well aware how greatly we 
are indebted to that able writer, and will readily leave the 
discussion of this point in his hands. 
IX. On the coloured Films produced by Electro^chemical Agency 
and by Heat. By R. Warington, Esq.* 
following paper is intended as an answer to a memoir of 
'“-the late Prof. Nobili on this subject, the translation of which 
appeared in the first volume of the Scientific Memoirs, p. 94<, 
under the title of a “ Memoir on colours in general, and par- 
ticularly on a new chromatic scale deduced from metallo- 
chromy for scientific and practical purposes.” As this paper 
contains a great detail of matter on the physical characters and 
properties of colours and coloured films, and as it is only with 
respect to the chemical part of the subject that I propose 
treating it, it will be necessary to extract such sentences as 
refer more immediately to the questions at issue. I should 
not have ventured to attack a memoir coming from so 
high an authority as Professor Nobili, but from its having as 
yet elicited very little notice, and the views taken being so 
startling to the chemist and so perfectly original, I am in- 
duced to offer some practical experimental remarks on the 
subject. The memoir naturally resolves itself into two distinct 
subjects ; namely, the nature of the coloured films produced 
through the medium of electro-chemical agency; and secondly, 
those produced by means of heat ; these it is my intention to 
treat of separately and distinctly in their order. 
Professor Nobili dates his discovery of the electro-chemical 
appearances as far back as the year 1826, and the account of 
them was laid before the French Institute in November 1828, 
and by their advice the distinctive appellation of metallo- 
cliromy was adopted. The method by which these appear- 
ances are produced is thus described, p. 94< : “ A plate of 
})latina is laid horizontally at the bottom of a vessel made of 
glass or cliina. A platina point is vertically suspended over 
Communicated by the Author. 
