428 MEMOIR OF THE LATE DR THOMAS CHARLES HOPE. 
the conducting power of fluids, until the 18th January 1836, when he read, to 
the Royal Society of Edinburgh, the first part of a paper entitled, “Observations and 
Experiments on the coloured and colourable matters in leaves and flowers of plants, upon 
which acids and alkalies act in producing red, yellow, or green colours.” A second 
part of this paper was laid before the Society on the 21st of the following March. 
Although chemists have at all times used coloured vegetable infusions for 
indicating the presence of acids and alkalies, no researches appeared to have been 
made on the peculiar vegetable principle on which the acid and alkali acted ; and it 
was generally taken for granted that both descriptions of agents acted on one and the 
same principle. Dr Horr endeavoured to shew, by various experiments on the gene- 
ral colouring matter of plants, that vegetable infusions, which became red by the 
addition of an acid, and green or yellow by an alkali, contained two distinct prin- 
ciples, on one of which acids acted, and alkalies on the other. To the former he 
proposed the name of Lrythrogene, and for the latter that of Xanthogene. DEcAN- 
DOLLE had distinguished the colouring matter of flowers by the name of Chromule ; 
and Exxis speaks of the substance which may become green, red, or yellow, under 
different circumstances, as the colowrable matter of plants. The object of Dr Horr’s 
researches was to prove, that this matter was not an individual substance, but 
consisted of two distinct vegetable principles, which exist either separate or com- 
bined in different plants. He illustrated this by many experiments on different 
sorts of plants, and gave the results in eight tables. He shewed that all green 
leaves, all white and yellow flowers, contain only one of these principles, viz., 
Xanthogene, that all red and blue flowers, also all leaves with red colours, contain 
both Xanthogene and Erythrogene (with the single exception of Litmus, which 
contains no Xanthogene), and that red flowers abound in Erythrogene. The 
distinct nature of these proximate principles of vegetables he inferred from the 
different modes in which they are affected by chemical re-agents. 
In the same year Dr Hore made a communication to the Society “ On the 
Chemical Nomenclature of Inorganic Compounds.” He pointed out the disadvan- 
tages of the want of a discriminating and uniform nomenclature among teachers 
and writers on chemistry; and stated certain changes which he had for some 
time employed in his lectures. 
The changes proposed were— 
1. To discard the prefixes proto, per, super, sub, for compounds. 
2. To adopt rigidly the happy suggestion of Dr THomson, viz., to employ the 
Greek numerals to denote the number of atoms or equivalents of the base of a 
compound, and the Latin numerals for the number of atoms of the oxygene 
or acid. 
3. To avoid as much as possible the intermixture of Greek and Latin in 
numerical indications. 
