, 1913-08-09

EIOtH NuIlSNGl CodoO LllG AI6 SohNttooiOD
arises, rock waves go out on all sides, but man
irregular manner according to the kind Of
rocks through which they have to pass. 1t has
been found by experiment that the vibrations
20 through sand ut the rate of over 800 feet
per second but pass through granite at
over double that rate. Professor Milne, of
whose decease we have recently learned bv
cable, obtained in Japan velocities varying
from 200 #. per second to $50 fit. Much
higher rates have been measured, and in the
Charleston earthquake the American geolo-
gists made out the amazing rate of three
English miles per second. Still more re-
markable results were obtained by Professor
Milne, with instruments of extreme sensitive
ness at his residence at Shlde liz the KSle of
Wight. He showed that great earthquakes
traverse the entire globe, some of the waves
moving through the solid globe and others
following it's crust. He found that trem-
ors which reached his instruments from
the opposite side of the globe had travelled
at the extraordinary speed of ST miles per
second.
From the first colamn of the table it VIII be
seen that the recent shock was felt over a con-
siderable area, and it must be remembered
that it most likely extended much beyond
the limits Indicated, that is to say it pobn-
bly, including places from which no informa-
ton has yet been received, for instance, the rest
of Porto Rico on the one hand and the islands
north OF ST. Kits on the other. Taking, how
ever, the limits as including only the places
named in the table we should get q length
Of about $50 English miles from Ponce to
Gundeloupe and a breadth of about $50
English miles from St. Thomas s~outhwards
to the latitude of GuadeIoupe.
Turning now to the second column of the
table we must remark that it is necessary
to understand it more fully before proceed
ing further. Ia all the islands named &C.
cept Porto Rico the hours given are ac-
cording to what is called local time, that il
to say a time which is regulated by the APP
parent passage of the Sun over the meridi-
all of the place. In Porto Rico also it is q
matter Of course that natural lazy regulates,
the time, but there not without u conspicu-
Gus addition of what the militant sutfra-
gettea sneeringly call '~man-mu1e" law
The reason is that Porto Rico is a possession
of the United States ana has to follow the
laws of that country. What then is the
law as to the regulation OF tine in the U1i-
ted States2
The essential point is the division of the
whole Of that vast country, stretching out
over more than fifty five degrees of Iongi-
tude, into strips or zones lying north aud
south, each zone covering fifteen degrees Of
longitude, equivalent in time to one hour.
The zones are formed by taking the meri-
dams of IS, 80, 1O5, and 12O Us the centre
lines of the respective zones, each zone ex~
tending about u degrees on each side of
the controlling merldiun. 1t is necessary
to shy "about'' because the dividing lines,
OF the zones are moved to one side or the
other according to the requirements Of the
case. For instance, 1t would never dosto
carry the line through a town, thus giving
to near neighbours two different time sys-
TENS one hoar apart. AS a practical illus
trntion Of the working of the plan on the
railways we may take the following.
If we land in New York we find hat the
time there is the time of the 18th meridian,
and this rules over Is deg. OF longitude, y
on each side of the said meridian. If we
board q train for San francisco we find the,
same time used till we reach the limit of
the above zone and then enter the next,
that is to say the zone of the 10Th meridian
At this point (about 824 deg. w. we find in
our railway timetable the instruction: Pat
your watch back one hour The same
thing occurs when we reach the zone of
the 1O5th meridian and the zone of the 12Oth
n,oridian In short the Watch will have tn