Plate 7, Fig. 13, shows another experiment carried out in the month of March,1927. The day and night part of the experiment can easily be discriminated. We find in the lower half of the picture three distinctly marked lines. The explanation is very simple. It was a rather hot spring day, with bright sunshine falling directly upon the filter paper and after a relatively short time the first border line formed, the rising process stopped. Clouds passed over the sun for a short while, but it was sufficient to make the Silver nitrate rise again and stop after a few minutes.