62 
Calculated. Found. 
Copper 47*172 46*909 
Chlorine 52*828 53*091 
100*000 100*000 
The formation of this crystalline sublimate appears to 
take place as soon as the temperature of the marbles covered 
with sulphate of copper reaches about 800°. In all pro- 
bability a formation of copper chloride is constantly 
occurring as a necessary step in the decomposition of the 
hydrochloric acid and air, and when the temperature reaches 
the volatizing point of the chloride these crystals appear. 
As the greatest amount of decomposition of the hydi’o- 
chloric acid takes place close upon the temperature at which 
the chloride sublimes, the formation of this salt and the 
consequent loss of copper has been a fertile source of annoy- 
ance to the manufacturer. 
Mr. Deacon has recently completely overcome this dijffi- 
culty by the addition of sodium sulphate to the copper 
sulphate with which the marbles are impregnated. 
The presence of this salt prevents any formation of copper 
chloride, sodium chloride being volatilized, and copper 
sulphate remaining behind. This reaction is well seen by 
the change of colour from green to blue produced when a 
solution of sodium sulphate is added to one of cupric 
chloride. 
“Memorandum on Brown-stapled Cotton,” by Major R. 
Trevor Clarke. Communicated by Dr. E. Schunck, F.R.S. 
The nankeen colour, in cotton staple may be considered, 
I think, as a normal variational state, rarely met with in 
the present day, but very probably natural to the wild 
forms now nearly extinct and very imperfectly known. 
The two plants which have the best claim to be considered 
wild species that I have met with, namely, the Polynesian 
plant of Nuttall, and the Santo Paulo one of Mr. Aubertin, 
