FEBRUARY 29, 1884.] 
LETTERS TO THE EDITOR. 
A clock for sending out electric signals once 
an hour or oftener. 
Ir is necessary that the central clock of a system of 
controlled clocks should send out an electric signal 
once an hour, by means of which signal the controlled 
clocks have their hands set to time. 
It is often convenient to have such a clock send out 
signals oftener than once an hour: for example, at the 
University of Wisconsin a central clock automatically 
rings an electric bell in each recitation-room at the end 
of each hour, and also at ten minutes before the end of 
the hour, i.e., at fifty minutes and sixty minutes. 
There are many 
ways of accomplish- 
ing this end. One 
of the simplest of 
these is described 
below from a clock 
which is now in use 
at the Washburn ob- 
servatory to control 
by hourly signals a 
system of secondary 
clocks in the city of 
Madison. 
The apparatus was 
made in the Univer- 
sity machine-shops 
by me, and cost, per- 
haps, five dollars; 
and it is perfectly 
Satisfactory in its 
operation. Figs. 1 
and 2 represent the 
projection and sec- 
tion of an ordinary 
clock-dial, with a 
_ Ting of black walnut 
or ebony, B,screwed 
on it. 
Around the outer 
circumference of B, 
and about a quarter 
of an inch from it, 
runs the brass wire 
C. This wire is 
threaded from end 
to end, and, passing 
through the four screw-eyes k, k, is held to, and sup- 
ported by, the wood ring B. The two ends of the 
Wire are joined by means of a long nut, or thimble, b. 
Strung loosely on the threaded ring C, and at various 
points of its circumference, are the small brass nuts 
ad,é. Some of these are employed as jam-nuts, a, a, 
to prevent any tangential motion in the threaded ring. 
The walnut ring can be made of convenient thickness, 
so that the minute-hand will pass over it; and for final 
adjustment the minute-hand may be bent in or out 
to get the required contact pressure. A thin strip 
of platinum (VP’, fig. 3) is soldered to the under side of 
the minute-hand along the portion which traverses 
the walnut ring B. Around this point is fitted the 
small block, J, of bone or vulcanite, with its under 
face sloping upward to form a sort of inclined plane 
to precede the platinum point P’. A short piece of 
platinum wire of suitable size is flattened at one end 
(P, fig. 3); and the flattened part, secured to the small 
piece of vulcanite, s, is laid upon the walnut ring B. 
The other end is bent round the threaded wire C, and 
secured in place by means of the nuts e strung on the 
ring for that purpose. 
SCIENCE. 
243 
The points at which the circuit is made and broken 
are the platinum points P, P’. The minute-hand, be- 
ing carried around with its point P’ in light contact 
with the ring B, is sprung out when the inclined block 
I comes in contact with the projection of s; and, being 
carried along, the points P, P’, are brought together 
by the springing-back of the hand. The length of 
contact depends on the width of the point P, and may 
be varied at pleasure. ‘The circuit-wires are led from 
the works of the clock and the threaded ring respec- 
tively, and may be provided with suitable binding- 
posts outside the clock. As the ring C runs clear 
around the dial, a platinum point may be inserted 
anywhere in its circumference; so that any number 
of signals may be made during the hour, or those al- 
ready set may be easily changed. The nuts e on the 
threaded wire not only insure a good metallic contact 
with the platinum point, but aid materially in its ad- 
justment for a given time of contact. The device is 
simple, in that it requires no great delicacy of work- 
manship in its construction, and is of such a form 
that almost any clock will receive it without change. 
H. W. PENNOCK. 
Deafness in white cats, and statistics of deaf- 
ness and epilepsy in America. 
In my letter of the 4th inst. (Science, iii. 171) I 
drew attention to the remarkable fact, that white cats, 
if they have blue eyes, are almost always deaf. 
Darwin, in his book on ‘ Animals and plants under 
domestication,’ attributes the peculiarity to a slight 
arrest of development in the nervous system in con- 
nection with the sense-organs. He thinks there is 
nothing unusual in the relation of blue eyes and 
white fur; but in regard to the deafness, he says (ii. 
323), — 
