220 KANSAS CITY REVIEW OF SCIENCE, 
Depot, has been assumed to be 7 m. 5s. ‘This difference is probably correct to 
within one or two seconds. It has been deduced from actual measures, in which 
the effect of convergency of meridians, and the spheroidal figure of the earth has 
been duly computed. It is desirable, as early as possible, to determine the exact 
difference of time, to within a small fraction of a second, by time determina- 
tions made on the ground and by exchange of clock signals by telegraph. 
The signals themselves are always correct to the nearest half-second of the 
clock. The error of the standard clock is daily ascertained by standard stars. 
Fractions of a second cannot be sent out by the clock itself, unless a Hack-clock 
be used, and set to the fraction of each transmission. 
Now, a word as to the proposed time-ball. It might be a public convenience, 
and at little expense; and by a little adjustment and punctuality it could be made 
a visible indicator of correct time for thousands. It is entirely practicable to 
drop it from the Observatory; but in view of liability to interruption it would be 
safer for the operator at the Union Depot to do so by touching a spring at the 
first extra-break of the four o’clock signal. A light elastic hollow ball, several 
feet in diameter, and having the figure 4 conspicuously painted round the 
the margin of a great circle, could be easily run up a staff by a cord a few minutes 
before the time, and could be made to descend instantaneously at four o’clock, by 
the simple touch of a spring. I simply suggest this. We send the signals and 
leave it to others to make them as useful as possible. 
Very truly yours, 
C. W.. Peircnmrre 
Morrison OpservATORY, July 15, 1880. 
Nore.—The time-ball at New York is dropped by the first break of the Washington clock. ‘To prevent 
interruption from operators, the operator at New York presses against the armature of his relay, until a few 
seconds before the signal. 
THE ELECTRIC RAILWAY. 
Now that the possibility of an electric railway has been fairly put before the 
public by Dr. Siemens, we may expect to hear more about it before many years. 
The commercial advantages of the system must, of course, determine whether 
the Electric Railway will be extensively used or not. The question is not entirely 
one of economy of fuel; safety and convenience are elements which greatly affect 
the commercial profitableness of any undertaking, and these must be taken into 
consideration in making an estimate. 
As yet, the new means of locomotion has only been experimented upon ona 
comparatively small scale, but the results have been quite sufficient to justify a 
favorable conclusion being drawn. 
The idea of an electric railway is by no means new; little model engines, 
which ran backward and forward on a pair of rails, or round and round in a 
circle, were often to be seen in the windows of the shops of scientific instrument 
makers in the early days of electrical science, and the suggestion to apply the 
