i 
OBSERVATIONS 
made in different proportions, confirmed 
this opinion. 
(a) Calcined cobalt, i dram. 
Sand from Freyen walde, prepared, 
Fixed vegetable alkali, of each 3 
drams. , 
Thefe well mixed, and kept during two 
hours in a melting heat in a crucible, 
to which a cover was luted, gave a 
Very dark glafs; from which was obtain¬ 
ed a fine dark azure blue, by levigating 
it, and washing it with water, fo as to 
feparate the lefs heavy parts. 
(b) Half a dram of calcined cobalt, 
mixed with the former quantity of fand 
and alkali, and treated in the fame 
manner, gave a deep blue fin alt, fimi- 
lar to the above, and even of hull greater 
vivacity. 
fcj With the fame quantity of fand 
and alkali, was mixed 15 grains of cal¬ 
cined cobalt. This gave likewife a fine 
lively blue colour, very little lighter 
than the former. 
F 2 
Thefe 
