[Footnote 5: _Trans. Ophthalmological Soc_., 1881, p. 198.]

Again, Quakerism is a decreasing sect, weakened by yearly desertions
and losses, especially as the act of marriage with a person who is
not a member of the Society is necessarily followed by exclusion
from it. It is most probable that a large proportion of the
deserters would be those who, through reversion to some bygone
ancestor, had sufficient artistic taste to make a continuance of
Quaker practices too irksome to be endured. Hence the existing
members of the Society of Friends are a race who probably contained
in the first instance an unduly large proportion of colour-blind men,
and from whose descendants many of those who were not born colour
blind have year by year been drafted away. Both causes must have
combined with the already well-known tendency of colour blindness to
hereditary transmission, to cause it to become a characteristic of
their race. Dalton, who first discovered its existence, as a
personal peculiarity of his own, was a Quaker to his death; Young,
the discoverer of the undulatory theory of light, and who wrote
specially on colours, was a Quaker by birth, but he married outside
the body and so ceased to belong to it.





STATISTICAL METHODS.

The object of statistical science is to discover methods of
condensing information concerning large groups of allied facts into