274 DR. KANE ON THE CHEMICAL HISTORY OF ARCHIL AND LITMUS. 
further examine ; the others, which are red, he termed lichen-red (Flechtenroth), and 
the wine- red, pigment; and, finally, he looked upon the lichen-red as being the 
colouring material of cudbear and of archil. It is unfortunate that this beautiful 
series of researches should have been left imperfect, indeed useless as regards the 
requisitions of organic chemistry at the present day, by there having been no attempt 
made to ascertain the composition of the numerous substances described by Heeren, 
except two analyses by Liebig of small portions sent to him by Heeren, one of the 
pseudo-erythrine, and the other of a peculiar acid, the roccellic acid, which was found 
in the Parmelia Roccella, but which was looked upon by Heeren as distinct from those 
bodies which produce colour. These analyses, although, as might have been expected 
from the eminence of their author, quite accurate, yet from being isolated and uncon- 
trolled by the analyses of the substances allied to pseudo-erythrine, have remained up to 
the present day without leading to any further progress in this promising and exten- 
sive field ; and notwithstanding that there is little doubt of the phenomena having 
been described by Heeren with care and exactness, we still remain in total ignorance 
of the organic changes which produce those phenomena, and of the laws of composition 
and of mutual reaction which characterize the various substances which he isolated 
and described. For the purpose, therefore, of establishing a theory of the production of 
lichen-red from erythrine, no materials whatsoever have been contributed by Heeren. 
The investigations of Robiquet have led to results which have been found of more 
direct utility, in illustrating the history of archil, than those of Heeren. By analys- 
ing the Variolaria dealbata, Robiquet discovered therein a substance incapable of 
producing colour, which he termed Variolarine, and another matter of a saccharoid 
character, to which he gave the name of Orcine. By means of orcine, the red colour 
of the archil is produced ; this substance Robiquet also isolated, and gave to it the 
name of Orceine. Not content with the isolation of these substances, and the descrip- 
tion of the phenomena of their production and decomposition, Robiquet, and sub- 
sequently Dumas, entered upon the analytical investigation of their constitution, in 
order to determine precisely the manner in which orceine is formed from orcine. 
The experimental results, however, were such as to admit of different formulae being 
proposed, and hence new researches are necessary to ascertain whether the theory of 
Dumas or that of Liebig, regarding the constitution of orceine, is most correct. 
From the preceding sketch of what has been accomplished in this department, it is 
evident that, as far as concerns the higher objects of chemical investigation, nothing 
positive or fundamental has been done. Excepting the composition of orcine, no 
numerical result can be considered as fixed, and consequently no ground whereon to 
build a theory has been gained. But even in the mere qualitative part of the inquiry, 
very many questions arise, the solution of which is accompanied by great difficulty. 
What relation does orcine bear to the colourless substances described by Heeren ? 
In what relation do the orceine of Robiquet and the lichen-red of Heeren stand? 
Do the various lichens contain the same colourless substances ? or do they produce the 
