Page:Transactions NZ Institute Volume 25.djvu/655

 and yellow tints changed places quickly; finally a yellow spot was left in a yellow background; and, when I had apparently lost sight of the image, I opened my eyes and found it again on the page of the book I had been reading.

It was curious and interesting to note how the colours would change places for a moment—an orange sun would appear on a yellow background, and suddenly give place to a yellow sun on an orange background. These changes lasting only for a moment, made the taking of accurate notes almost impossible.

(3.) I looked at the bright streak of light of a kerosene-stove, shut my eyes, but allowed the light to fall on the lids. First a yellow streak with a green halo appeared on a purple background; the halo disappeared, leaving yellow on purple; then a blue streak on a purple background, the blue gradually darkening till it appeared black, on a purple-grey background. This gave a negative image.

(4.) On trying the same experiment; but covering my eyelids, I found the image did not last as long. The yellow streak turned to orange, then to green with yellow halo, changing into dark-green, and then into a dark streak, the background being purple, varying in shade.

(5.) One evening I was walking up the Coote Road, when the presence of a persistent after-image showed me that I must have been looking unconsciously at a bright light. On recalling the circumstances I came to the conclusion that the light might have been that of a candle in the room I had just left, or that of the lamp at the corner opposite Russell's store. I walked quickly up Shakespeare Road and Clyde Road, but the image would not leave me until I reached the turning to Brewster Lane.

Examples and illustrations might be continued indefinitely, but I think I have said enough to prove that positive images change into negative, and it would be interesting if it could be shown that the changes of colour followed a fixed rule, as I am inclined to think. But, as I said before, experiments are trying to the eyes, and I found I could not continue my observations for long at one time.

I have been unable to obtain access to the latest researches on this subject, which is an interesting one, as it forms an introduction to the great subject of mental reproduction. 