deficiency of oxide of iron in such soils. Liebeg 
says, however, It must be ammonia (an alkali) 
which forms the red and blue colouring matters of 
flowers. ” 
On no subject is human knowledge more defect- 
ive, than that of the production, and changes, of 
colours. Several theories have been promulgated 
in different ages, but still none that has been gene- 
rally accepted. Although astonishing advances in 
science have lately been made, still our knowledge 
on this head, may well keep us humble minded. 
A few facts, proved by Dr. Lewis, may interest 
our readers more than speculation. Yellow flow- 
ers, unlike all others, communicate to water or to 
spirit of wine, durable yellow colours, not alterable, 
but in degree, by acids or by alkalies ; the former 
only rendering them paler ; and the latter render- 
ing them deeper. Wool or silk, impregnated with 
a solution of alum or tartar, receives, on being 
boiled with the watery infusion or decoction, a 
durable yellow dye. A durable yellow lake is pre- 
pared, by precipitating with alum, an infusion of 
yellow flowers made in an alkaline ley. In some 
of the orange coloured flowers, the yellow matter 
seems to be of the same kind as that of the pure 
yellow flowers; but the red matter seems to be 
diflerent from that of the pure red flowers. The 
yellow matter is extracted from these flowers by 
water ; and the remaining red matter is extracted 
by spirit of wine, or by a weak solution of a fixed 
alkali, in water. This curious instance of discre- 
pancy in two colours, has been noticed under Car- 
thainus tinctorius. No. 162, 
