of Edinburgh, Session 1884-85. 
191 
2. The main constituent, urushic acid, is a stable acid, capable 
of forming many well-defined salts and derivative compounds. 
3. The gum is probably identical with gum arabic. 
4. The nitrogenous matter has a composition allied to albumen, 
with much less nitrogen, and has a peculiar diastatic property. 
5. The hardening of the juice is due to the oxidation of urushic 
acid (C 14 H 18 0 2 ) into oxy-urushic acid (C 14 H 18 0 3 ), which is effected 
by the aid of the nitrogenous matter in presence of oxygen and 
moisture. 
6. The hardening can only take place within narrow limits of 
temperature, viz., bet ween 0° to 2° C., on one side, and the temperature 
of the coagulation of the albuminoid (60° to 70° C.) on the other. 
7. The gum is essential in keeping up the emulsion and uniform 
distribution of the constituents ; but in the hardened lacquer it is 
injurious, causing blisters on newly lacquered ware when treated 
with water for a length of time. 
8. Any quality can be conveniently given to the juice by the 
addition of pure urushic acid, which brings down the relative 
amounts of gum and nitrogenous matter. The lacquer becomes thus 
more transparent and gains in strength. 
9. The mixture of 20 to 25 per cent, of drying oil with the 
juice does not much impair the essential quality of the lacquer. 
4. On Atmospheric Electricity at Dodabetta. By Professor 
C. Michie Smith. 
5. Eecent Photographs of Stars, described by C. Piazzi 
Smyth, Astronomer-Koyal for Scotland. 
For many years past some little amount of isolated work has 
occasionally been accomplished in photographing certain of the 
brighter stars. But lately, stellar photography has gone forward 
with leaps and bounds ; so that at a dozen different Observatories 
in Europe, America, South Africa, and Australia, so much is now 
being done in that line, that there is a speedy prospect of, in a 
manner, the whole sidereal heavens being photographed, and after a 
fashion that would not only have astonished Hipparchus, but been 
