The Princeton union. [volume] (Princeton, Minn.) 1876-1976, 1893-12-14
SCIENCE AND INDUSTRY.
REFORMATION CONCERNING USEFUL
ARTS. -r.E

A Method Of Measuring the Vibra-
lions of Tall Buildings by a Photo
graphic Process-Nhat Il Steams-
Automatic Starter aad Time Re-
cUrsQcr.
Prof Steiner OF Prague has perfected
method Of accurately measuring
bridge and floor vibrations by the :lid
OF photography. His process is a deli
cate one, and is an appMca ton of the
chroro-phc tographic process of NJ. e.
J. Marcy, of the Institute of France.
He uses little glass balls, aud these
are strongly Illuminated, either by a
solar ray, or by an electric arc light,
Or Il magnesium light.
These balls give upon a photogra phic
negative clear and we'll defined point
10 register vibrations one Of these glass
balls is fixed at the point to be exam
ined, and the photographic apparatus
is then so set up that the image Of the
ball falls on the right edge Of the
plate. The plate is exposed 1t the
moment the movement commences, and
at the same time the camera is turned
from right to left on a pivot. The mega
1--WE then shows an undulating line
' Inch is the vibratic MS Of the ball point
in amplitude and duration
10 obtain scale with which to read
this undulatEag line, second ball is
suspended to fixed point, to which is
given a known rate of oscillat ton. The
POSITION OF these two oalS is such
that their images coincide in a state Of
M, ~
OF the second ball as printed upon the
line Of the first on a negative gives
tie number Of vibrations of the latter
in a given time
1t is possible then TO place near the
INST ball fixed scale brilliantly il
Illuminated like the bail itself. and as
tlls scale appears on the negative the
amplitude of the oscillations can be
II ensured at a glance. The measure
II entS may be made either directly
upon the print or from an enlarge
ment made in the usual manner. TO
avoid the practical difficulty Of making
the images of the two balls coincide at
the beginning of the opera ton. Prof
Steiner says a pendulum may be made
to oscillatc before the source Of H.
Elimination of the ball.
The ball of this pendulum will pass
before the light at regular and deter
MIXED Intervals, and the undulating line
or the negative will be broken at dis
t3lces corresponding to the duration
or an oscillation of TIL pendulum. 1t
is not important that the camera turns
upon its axis with Il uniform motion:
ana the speed Of turning is likewise of
little imports nee.
The relations of the curves traced
by the two balls will always remain
the same. 1t is sugge ted that al:
apparatus Of this kind would be useful
III studying the vibrations of the floors
or buildings resting for some years
CT iron 'cams, especially when these
floors are submitted to the Rhythmic
Stock Of dancing.-La Genie Civil.
An Ideal Rapid Transit System.
Eelgians are e1ni1.e ntly iml ued With
Tie progressive spirit Of the age. The
magnificent city OF Brussels has found
tt at surface cars, no matter how we'll
handled, are no longer equal to the
requirements Of the passenger traffic.
AID an early termination to such dis
comfort as Londoners are yr71,nblinp
' -A'' -'S" AOlhcrS seem 10 DC help
hssiy resigned to, is to be made ly
the construction Of an underground cleo
trio road. The average depth of the
stations will be liz feet; the best foru,s
or American electric elevators are to
be Used, and there will be great I'M
proTemcnts on the City and South
electric underground road in the impor
taht ma tier OF ventilation: in fact, when
the scheme is carried out Brussels will
DC able to boast not only Of some OF the
hneSt thorouGhfares in Europe, but of a
system or local transit SURPASSED by
none. There will be two tunnels, each
used exclusively by trains in one dircc-
ZION The tunnels will be either. mar
ailel or one above the other following
always the line Of public streets, and
OWING to the depth no damage can DOS
sloly result to the surface structures.
OIe great advantage of this system is
lhat lne work OF driving the tunnels
can De pushed on from the respective
stations 1T the sane time. and it is OK
pected that the undertaking. win ha
completed IN two years This will lc
accolnpl shed, of course, without tho
least obstruction to traffic in the streets
When tho tunnels are COMPLETED thc
shafts sunk to the stations will be used
Tor hits 70: the conveyance Of pas
Sc rsers from the street levels to the
traln platforms below. TRIMS will run
every TWO Or two and ODe-hnlf minutes.
;nu the speed will not exceed twenty,
hVH Inilo' per hou. The cars will be-
primarily Illuminated with electric
lights, and the temperature will be
ccol Ill summer and warm in winter
lhtSe are interesting facts for be-
lated New York to ponder on. and nos
sloly 1t may derive further encourage
lrcnt and incentive to get I'D and he
doing from the announcement that casv
going Madrid is SOFA to have it's Icen
Ill foreground electric road.
AUTOMATIC" Starter and Time pacora
In these days of record breaking in
horse racing, pedestrianism and h;cv-
cling fraction of second is often ,
matter on which important issues do-
pend. 1t would seem that absolute 49,
1n