FEBRUARY 15, 1884.] 
LETTERS TO THE EDITOR. 
Deafness in white cats. 
I AM engaged upon an investigation concerning the 
eauses of deafness; and I have therefore naturally 
been much interested in Mr Lawson Tait’s paper 
concerning deafness in white cats, published in 
Nature (vol. xxix. p. 164), and in the letter of Mr. 
Joseph Stevens, published in the same journal, con- 
cerning his father’s breed of deaf white cats (vol. 
=xix. p. 237). 
I have myself come across three instances of white 
cats with blue eyes (two in Europe and one in Ameri- 
ca), and in each case the animal was deaf. 
Mr. Tait’s statement, that ‘‘ congenital deafness is 
not known to occur in any animal but the cat’”’ is a 
most extraordinary one, in view of the great preva- 
lence of congenital deafness among human beings. 
Of the 33,878 deaf-mutes in the United States, 
more than one-half are congenitally deaf;! and in 
Europe (excepting Germany) the proportion of ccn- 
genitally deat appears to be much greater, — about 
four to one, according to the late Dr. Harvey L. Peet 
(1854).? 
Why should congenital deafness among the lower 
zannals be confined to cats, and why only to white 
cats ¢ 
Mr. Tait notes also an apparent association between 
epilepsy and whiteness in animals. He says, ‘‘ Every 
kind of white animal I have kept as a pet has been 
the subject of epilepsy; and the association is sugges- 
tive when we are told, as I have been frequently, 
that the disease is unknown among negroes,’’ 
It is worthy of note, that deafness also appears to 
be less common among negroes than among white 
people. According to the recent census, the total 
white population of this country amounts to 43,402,- 
970, and the total number of white deaf-mutes is 
30,661. The colored population is given as 6,580,793, 
with 3,177 colored deaf-mutes (not including Chinese 
and Indians). 
Thus, while we have one deaf-mute for every 1,416 
of the white population, we have only one deaf-mute 
for every 2,070 of the colored people. It would be 
interesting to know whether the proportion of con- 
genitally deaf is less among the colored than the 
white deaf-mutes. 
The pallid complexion of many deaf-mutes has 
often been commented upon by strangers as an ap- 
parent indication of ill health. While I cannot say 
that I have myself observed this as a common char- 
acteristic, still my attention has never been specifi- 
cally called to the point. It would be easy to test 
the matter by collecting into one room all the con- 
genitally deaf pupils of some large institution, exclud- 
ing those pupils who became deaf from accidental 
causes. A cursory examination would probably show 
whether there is or is not, in the human race, an asso- 
ciation between congenital deafness and the absence 
of coloring-matter from the skin and hair. I trust 
that some of your readers may be able to throw light 
upon these points. 
ALEXANDER GRAHAM BELL. 
Washington, D.C., Feb. 4, 1884. 
Radiant heat. 
In a letter to Science of Jan. 25, Mr. Fitzgerald 
thinks it is possible that I am misled as to the manner 
in which my rotating-screens work, by reason of the 
complication of the arrangement. I must never- 
theless continue to assert, that I think I understand 
1 See Compendium of the tenth census (1880), part ii. p. 1664, 
* See American annals of the deaf and dumb, vol. vi. p. 287. 
SCIENCE. 
171 
how the process I have invented operates, and cannot 
admit that Iam in error in this until such error is 
pointed out. Now, Mr. Fitzgerald’s demand that I 
should show that the heat which originally came 
from B is returned to 6 in the same direction as the 
heat coming from A, would incorrectly lead the reader 
to suppose that I made some such statement or sup- 
position in the original paper, and that consequently 
I was misled, as he suggests. But the most super- 
ficial examination of the paper shows that I have not 
fora moment supposed this; as I have simply proposed 
to so arrange the reflecting surfaces as to return radia- 
tions from B through some one or more of the aper- 
tures in the screen b, and not necessarily through the 
apertures from which they originated. It necessarily 
follows, that I did not suppose them to be returned 
in a direction parallel to the radiations from A. 
I think, then, that Mr. Fitzgerald must certainly 
admit that I have not made the blunder which is im- 
plied in his letter. 
Again: Mr. Fitzgerald takes it for granted, appar- 
ently, that this want of coincidence in direction would 
be fatal to the process; whereas, in my estimation, 
the only question is, whether the radiations which 
originally came from B are returned to 6 or not. 
What their direction may be appears to me entirely 
immaterial. 
If it is possible to show that the want of coin- 
cidence in the direction of all the rays coming to b 
invalidates the process, as Mr. Fitzgerald implies, he 
will no doubt be able to give a direct proof of the 
fact. Such proof, however, seems to me impossible; 
for, after the energy reaches B, the path by which it 
has arrived is of no consequence. 
It goes without saying, that in this view of the 
matter it is quite impossible to substitute the process 
proposed by Mr. Fitzgerald in place of mine; asin his 
process these directions necessarily coincide, which 
in mine cannot coincide. 
1 mM n 
i q i 
L —— tp For 7 z 
I 1 1 B 
0’ € y’ a Saal 2’ 
! i ] 
Fig. 1. 
l | I 
x Ye 
A ) I eee I B 
a y’ 2 
I I 
Fie. 2. 
I ] 1 
a yY ~& 2 
A i i i B 
a’ 43- y’ 2” 
I | I 
Fi4. 3. 
| I ! 
Ay y ze 
A i ber seen i B 
De Yo ——___—__—+9e_ 
I { | 
Fre. 4. 
It does seem possible, however, to employ two sets 
of openings such as Mr. Fitzgerald has proposed, in 
such a way that they shall together accomplish what 
neither of them can effect singly. For example: let 
there be three fixed screens, 1, m, n, with two sets of 
openings, % y 2, w y’ 2, which can be opened or 
closed instantly; and let them all be closed except 
when the contrary is explicitly stated. Let each of 
the four equal intervals of time which we shall speak 
