best Methods of producing artificial Cold. 289 
Fig. 8. a thermometer, with the lower part of the scale- 
board turned up with a hinge, for the convenience of taking 
the temperature of small quantities, or of mixtures in which 
mineral acids forrrr a part. , 
N. B. These vessels are represented as in glass, that being 
undoubtedly fittest for purposes in which corrosive acids are 
to be used. 
