414 Testing for Colour-blindness. CJ uly, 
55 failures reported in examinations for colours only. This, 
I assume, implies that a number of persons voluntarily offered 
themselves for the colour-test certificate before going to sea, 
and paid their shillings to satisfy themselves of their inability 
to distinguish colours commonly in use. 
Many typical cases of complete and incomplete colour- 
blindness are given, and the subjoined summary more clearly 
shows the particular mistakes made by the 85 candidates 
already referred to. 
Colours of cards 
or glasses. 
Green. 
Red. 
Yellow. 
Blue. 
Other 
colours. 
Green described as 
— 
79 
16 
13 
13 
Red ,, 
24 
— 
3 
3 
3 
Yellow ,, 
9 
38 
— 
1 
2 
Blue ,, 
45 
2 
1 
— 
4 
Black ,, 
4 
2 
— 
— 
3 
White 
3 
I 
— 
— 
— 
Since the report does not state the total number of persons 
examined within the year, or the past four years, I am un- 
able to give the exaCt percentage of rejections ; but it may 
be assumed that it does not greatly differ from that of 1877 
and 1878, which was rather under | per cent. It is believed 
that last year it stood rather higher, 0^6 per cent. 
The hereditary nature of colour-blindness is a curious 
feature in the case. It is apparently known to but com- 
paratively few persons that colour-blindness is transmissible, 
affedts the human race in different degrees, is an incurable 
physical affeCtitfn, and remarkable enough is chiefly confined 
to the male branch of families. A seleft instance or two 
from among many will serve to impress the first feature on 
the memory. In a family of seven children, four sons and 
three daughters, the sons are more or less colour-blind. 
The defeCt in this case is inherited from the grandfather, 
through the mother, whose vision, as also that of her three 
daughters, is quite normal. In another family of five children, 
three sons and two daughters, the sons inherit the colour-blind- 
ness of their father and grandfather, while the two daughters, 
and, indeed, all the females, for three generations at least, 
have been free from any colour defeCt. 
My reason for referring to the hereditary nature of colour- 
blindness is that I wish more particularly to enforce a duty 
upon parents, one they owe to themselves and their children, 
that of making due inquiry into every peculiarity or defeCt 
of vision which may have constituted a family failing, before 
