154 On the Invisibility of certain Colours to certain Eyes. 
milies. Mr. Huddart mentions the case of one Harris, a shoe- 
maker at Maryport in Cumberland, who could only distinguish 
black and white, and he had two brothers almost equally de- 
fective, one of whom always mistook orange for green. Harris 
observed this defect when he was four years old, and, chiefly 
from his inability to distinguish cherries on a tree like his 
companions. He had two other brothers and sisters, who, as 
well as their parents, had no such defect. Another case of a 
Mr. Scott is recorded in the Philosophical Transactions, in 
which full reds and full greens appeared alike, while yellows 
and dark blues were very easily distinguished. Mr. Scott’s 
father, his maternal uncle, one of his sisters, and her two sons, 
had all the same imperfection. Our celebrated chemist, Mr, 
Dalton, cannot distinguish blue from pink by daylight; and 
in the solar spectrum the red is scarcely visible, the rest of it 
appearing to consist of two colours, yellow and blue. Dr. But- 
ters, in a letter addressed to the editor of this work, has de- 
scribed the case of Mr. R. Tucker, son of Dr. Tucker of Ash- 
burton, who mistakes orange for green, like one of the Har- 
. rises. Like Mr. Dalton, he could not distinguish blue from 
pink; but he always knew yellow. The colours in the spec- 
trum he describes as follows: P 
Le HedcmistaksenfOriasciisisas selb tel fal SS aN brown, 
DQ ORANGE jin dite eh oud Gs, 0) ele ele ewe eo ef BTOCRDY 
3. Yellow, generally known, but sometimes taken for orange, 
4. Green mistaken for ..... 5 ol sSlnpIRG make . orange, 
Be Blusomdslh iShiasussahe ois 03> Sith. ewes .. pink, 
Gidding; sswatseidjbecis cae mer/ene, ssi 3a) <) 1st of Miele be purple, 
Fxg Vlolstia is At sip aristtiene, Wis toa 20s es odes purple. 
Mr. Harvey has described, in a paper read before the Royal 
Society of Edinburgh, and which will soon be published, the 
case of a person now alive, and aged 60, who could distinguish 
with certainty only white, yellow, and gray. He could, how- 
ever, distinguish blues when they were Tight. ‘Dr. Nichols has 
recorded a case where a person who was in the navy purchased 
a blue uniform coat and waistcoat, with red breeches to match 
the blue; and he has mentioned one case in which the imper- 
fection is derived through the father, and another in which it 
descended from the mother. 
In the case of a young man in the prime of life, with whom 
the writer of this article is acquainted, only two colours were 
perceived in Dr. Wollaston’s spectrum of five colours, viz. red, 
green, blue, and violet. The colours which he saw were blue 
and orange or yellow, as he did not distinguish these two from 
one another.. When all the colours of the spectrum were ab- 
sorbed by a reddish glass, excepting red and dark green, he 
saw 
