Intensity and lustre, however, are certainly important.

It is possible, by carefully choosing a room of pretty constant daylight illumination, and setting the experiments at the same hour each day, to secure a regular degree of brightness if the colours themselves are equally bright; and lustre may be ruled out by using coloured wools or blotting-papers.

The papers used in the experiments given above were coloured blotting-papers.

The omission of yellow is due to the absence, in the neighbourhood, of a satisfactory yellow paper.
The method now described may be further illustrated by the following experiments on the use of the hands by the young child.
_The Origin of Right-handedness._--The question, "Why are we right or left-handed ?" has exercised the speculative ingenuity of many men.

It has come to the front anew in recent years, in view of the advances made in the general physiology of the nervous system; and certainly we are now in a better position to set the problem intelligently and to hope for its solution.