223 
1916-17.] On some Nuclei of Cloudy Condensation. 
by the point discharge are very few, owing to their being deposited by the 
electricity, and one discharge of the electrophorus gave as great an effect as 
many discharges, owing to each succeeding discharge undoing the effect of 
the previous one. Little difference was found if there was no outlet for 
the electricity, the only wire entering the flask being the one with the dis- 
charging point (see test 5). The glass seems to act as the other electrode. 
Spark Discharge. 
The discharging point was now placed near the other electrode so that 
a very small spark could pass. The result is shown in test No. 6. The 
number of nuclei was now greatly increased, and many of them were large 
enough to be active with a 2 per cent, expansion. When blunt electrodes 
were used, with a greater distance between them, and a more powerful spark 
from a small induction machine with two small Leyden jars, the nuclei gave 
an extremely dense fog with the slightest supersaturation (see test No. 7). 
After remaining eighteen hours the nuclei were tested. When all the large 
nuclei had been disposed of, only one shower remained which required more 
than 2 per cent, expansion. These tests show that the number and the size 
of the nuclei can be changed by altering the length and density of the 
discharge. 
Sulphurous Acid and Light. 
The nuclei produced by the action of sunlight on sulphurous acid was 
tested by placing a little of the diluted acid in the flask Y and drawing the 
air into the test-flask. With short exposure to light there were a number of 
small nuclei requiring more than a 2 per cent, expansion, but none large (see 
test No. 8). A longer exposure to light gave a dense fog with the slightest 
expansion. 
Sulphurous Acid and Electric Discharge. 
If a very weak solution of sulphurous acid be put in the flask V and 
an electric discharge be made in it, a great number of small nuclei are 
formed (see test No. 10). With stronger sulphurous acid, the condensation 
was very dense with the slightest expansion. This greater effect of the 
electric discharge produced by the presence of sulphurous acid over that 
given by air is probably due to the peroxide of hydrogen and nitrogen 
compounds formed by electric discharge. 
Tests in Pure Air. 
It was thought that some information might be obtained by an examina- 
tion of the nuclei in purer air than can be obtained in this district. Loch 
Awe, where on a previous occasion some investigations were made in 
