Evening star., 1909-09-03
SCIENCE NOTES.

An interesting dredge, which is auto
matte in its operation, has been working
on the river Volga, in Russia for some
time for the purpose of maintaining a
level river bottom by moving the dirt
from the high places and depositing it
at the low spots. The dredge is the in
vention of a Russian nobeman. Baron
Nicolas Tominf. Beneath the craft there
is supported a screw, by which the roll
is gathered up. There seems to be al
most no limit to the width OF the chan
mel that may be cut by this dredge The
screws cutting surface may be increased
as desired by the addition of sections so
that in some instances as much as go
feet has been operated. The inventor is
of the opinion that this is not of the pos
sible length. He says he sees no reason
why the screw should not be made 600
feet long If found desirable. The power
which drives this dredge is derived from
the current of the stream on which it is
at work. In operation these sections are
secured together to the desired length on
the shore and then launched into the
stream, where the line Of screws is Sc
cured in beneath the dredge. When the
craft is moved into a position where the
full force of the current is encounterei,
the machinery is automatically set in
motion and the work proceeds This
novel piece of mechanism has attracted
the general interest of engineers abroad
and has been heartily indorsed by many
of them. BY recent improvement it Is
possible to deposit the soil on scows for
removal to more distant points where its
presence may be desired
By substituting disks of carbon for the
rods of the same material it has been
made possible to greatly reduce the size
of the arc lamps and at the same time
TO present a lamp which will burn 80
per cent longer without renewal. These
are important improvements. The eff
cheney of the arc lamp has always been
limited by reason of the unequal con-
sumption of the carbon rods, which have
mad tendency to burn faster on one side
than another, and in this manner a per-
feet contact of the two ends was posi-
BILE only occasionally. In the new de-
sign which makes use of the carbon disks
the latter are revolving all the time the
lamp is in use and the arc is made at
the edges of the two disks. The 1O-am-
pere lamps of this design are but twenty
inches over all.
Sanitary car straps for those who are
compelled to stand in the street ears
are being tried in some of the under
ground cars in use in New York. The
new strap consists of a steel rod
which is suspended from the roof and
having porcelain handle at the lower
end These may be kept absolutely
clean, whereas a recent examination of
a car strap which had been in service bur
a comparatively short time was found 10
be reeking with all kinds of germs.
The cost of filtering water by the slow
sand method Is given as follows in the
1907 report of the Lawrence, Mass, water
board During that year 1.193, ,O35. .S79
gallons were filtered at a total cost of
s11.544.92. or about $9.6S per 1000, 900 gal
lon. The itemized cost per 100000 gallons
was. Removal OF ice and snow 81 Ga4 .
scraping. $1.455 sanding. SO.S7: washing
and conveying sand, $1.S49; filter main
tenance and extras $1.SS6; care of
grounds, $O.52i.