The Savannah morning news., 1904-05-07

regularly produce an attack of dem
que in a non-immune by submitting
the latter to the attack of mosquitoes
which had fed on suffers from the dis
ease. In one experiment he carried
dengue-infected mosquitoes to a noun
tain town 5000 feet in altitude, where
there were no mosquitoes and no dem
que. One of the natives was shut up
in the room with the mosquitoes, and
on the fourth day came down with
sharp attack of dengue, and a second
presented the typical symptoms on the
fifth day. The mosquitoes were irnnle-
diately destroyed and no further cases
occurred. DR.. Graham also claims to
have discovered the germ which causes
dengue in both human blood and the
stomach Of the mosquito. 1t re-
sembles. some forms of the malarial
parasite.
An official report of the Depart
ment of Bridges and Roads in France
shows the continuance of the good
results obtained in rendering roads free
from dust by coating the surface with
tar The engineer for the Seine and
Marine departments report that after
an unsuccessful trial of a mixture Of
oil and petroleum a coating of tar
was in the summer of 1902 laid down
on seven different lengths of road. Az
ter carefully observing these during
period of twelve months. he finds
that dust and mud have wholly dis
appeared and the cost of maintenance
of the roads has been considerably re-
I duced. Further comparing the previous
outlay on the roads with that of those
with tarred surface, he says: 1T ap-
pears that the tarring method re-
quires no greater outlay, and at the
same time very considerably improves
condition of he
Cher two lengths of the Chausee Ma
t1onale were coated with tar in June
and August of 1902. Both these expert
lnents have been entirely successful
the road now being covered with an
elastic skin, while the sound of foot
passengers tread is muffled and horses
ana draught oxen require only one
nalt the effort they put forth before
The noise and vibration caused by
Venlcular traffic is much reduced. and
neither dust nor mud is formed on the
tarred surface"
When a popular camera. was first
under consideration, it became neces-
sary to secure good lens at a popu-
lar price, says a writer in Outing.
This was possible only by the devils
ing ana making of special machinery
ana tools, and by buying the raw
grass and manufacturing in large GUAM
titles. Lens glass, as all the world
KNOWS, or will after this story is pub
hshed, is made principally in Ger
many France and England. Brought
20 the manufacturer in small slabs.
II IS cut by revolving saws into the
olHerent sizes and then subjected to
series OF grindings and polishings
tnaI must eventually enable the tester
70 NJ the lens over an absolute form
OF the shape and size required, so per-
1ectiy that deviation of one two
lnlllonth OF an inch is instantly de-
tected. The cement used for building
up lenses from single glasses is
preparation so delicate that II cannot
eIter this perfection. The making Of
lenses for Photographic work has now
become an immense industry. and in
many cases the shutters are also made
IN conjunction Highest skill is en-
pioyed to perfect this first requisite
OF the apparatus; but careful as these
makers are to prove their work. the
lenses are also always thoroughly test
ed by the camera experts. This doem
not mean that they are subjected N
anything like the different tests the
amateur will apply later on; but they
are ascertained TO be Of correct finish.
iocus ana mount and the focal scale
IS tested by objects at the stated dis
tances; the finder is brought info
alignment, and then the camera needs
only the final touching up of rubbed
Spots 10 be ready for the market.