486 
Proceedings of the Royal Society of Edinburgh. [Sess. 
electrical conditions into the sunning flask, and to avoid making another 
hole in the stopper a brass tube was substituted for one of the glass ones, 
the brass tube forming one connection and a wire the other. The results 
were most successful, and it looked as if the electrical conditions had solved 
the problem, as the salt and iodine were steadily fog-producing under 
the action of sunshine. But now the cross-examination of the apparatus 
began. First, the electrical connections were broken, but still the salt and 
iodine steadily responded to the sunshine. The brass tube was now taken 
out and a glass one put in. All action ceased. An examination of the 
part of the brass tube that had been inside the flask showed that the 
vapours had slightly discoloured it ; there had evidently been some 
chemical action on the metal, and it seemed possible that the products of 
this action might have made the gases active. An answer to this question 
was obtained by retaining the glass tube and putting a piece of brass 
in the sunning flask, to see if it would make the gases active : but there 
was no condensation with it, nor with zinc or copper, showing that the 
activity with the brass tube was not due to any action on the metal. 
Attention was again directed to the brass tube. The end which entered the 
flask was now highly heated in a bunsen flame to cleanse it. The other 
end of the tube could not be highly heated, as there were some attachments 
put on with solder. The tube was then returned to the flask. On again 
sunning for one minute, the gases gave no condensation ; but if some 
minutes’ sunning were given, a dense fogging appeared in the test flask as 
before. The only explanation I could think of was that the upper part of 
the tube had not been purified by the heating, and that when plenty of time 
was given the gases diffused up to the impure part of the tube. To test 
this, the air in the flask was drawn up to the upper part of the tube and 
allowed to go back. When this was done, one minute of sunshine was 
ample time to give a dense condensation ; thus showing that the first 
hopeful results obtained with this apparatus were due to some impurity 
in the inside of the brass tube, which made the salt and iodine active. 
This conclusion was confirmed in other ways. 
Hydrochloric Acid and newly prepared Gases. 
So far the investigation had thrown but little light on the occasional 
activity of salt and iodine. Attention was next directed to the other con- 
stituent of sea-shore air, namely, hydrochloric acid. Some weak acid was 
put in the sunning flask and its vapour sunned, but when proper care was 
taken there was no response ; the air and acid vapour gave no condensation 
