Chap. 24.] ' wp&thetfc Ink. 137 



trunks of trees, houfes, &c. may be painted with com- 

 mon colours, fo as to reprefent winter. The verdure, 

 the fruits, and the flowers, may be depicted in dif- 

 ferent {hades of the two inks, On approaching the 

 fire the landfcape will gradually be changed from a 

 winter to a fummer fcene. The trees will begin to 

 fhoot out their foliage, and the flowers and the fruits 

 will, by degrees, aflume the appearance of maturity. 

 The vivid parts will again fade, on being removed 

 from the heat, and the landfcape refume the wintry 

 ^fpecl. 



It was formerly thought that the green colour pro- 

 duced by heat in the fympathetic ink of cobalt, arofc 

 from- the metallic fait being cryftallized, and afterwards 

 attracting a fufficient quantity of water from the cold 

 air to diffolve it, and caufe it to difappear j but it is 

 proved, that the marine fait of cobalt, diflblved in 

 water, affumes the fame colour when expofed to 3, 

 certain degree of heat. 



The vitriolic acid in a concentrated ftate does not 

 diffolve cobalt without the affiftance of heat, when the 

 acid is decompoled, and comes over in fulphureous 

 fumes. The cobalt is in part calcined, and in part 

 converted into a cryftalline fait foluble in water, and 

 which may be precipitated by lime and by alkalies, in 

 the form of a rofe-coloured powder or calx. Diluted 

 vitriolic acid acts upon the calx of cobalt, and forms 

 the fame fait. 



Cobalt unites with all the metals except filver, lead, 

 quickfilver, and bifmuth, but does not produce arty 

 remarkable or ufeful compound with any. It is fe- 

 parated from acids by zinc in the form of a dark- 

 coloured powder, but not by iron. 



A mixture of nickel with the calx of cobalt very 

 much injures the colour which the latter communi- 

 cates 



