The National tribune., 1885-07-30
SCIENTIFIC CHAT.

"A tadpole, the larva of frog, has a tail and no
legs, gls instead of lungs, heart precisely like
food and a spiral intestine to digest it. With the
approach of maturity the hind legs appear then the
front pair; the beak falls of, the tail and gills
waste away; the lungs created; the digestive
apparatus is changed to suit the animal diet; the
heart becomes reptiian in type by the addition of
another aurcle; in fact skin, muscles, nerves and
bood-veSSelS vanish, being absorbed atom by atom
and q new set is substituted.
The limitation of yellow fever to restricted
areas Is one of the characteristics of this disease
even when epidemic. and it takes some curious
phases The specific gravity Of the poison is great.
and it clings to surfaces. Frequently its rate of
progress may be mathematicaly defined, - says DR..
+. w. Reilly, 80 many feet per day, indepen-
dent OF any recognized influence except perpen-
dcular obstacle. In Mobile board fence stopped
its progress, and q bluff bank held it at bay for
weeks in Memphis. Hence the value of removal
and the sanitary line when this disease appears.
"A Hungarian statistician has been studying the
effect of comfort on longevity. His tables show
that the richest people have an average life of So
years, the mdding 46, and the poor only Az. A
wellto-do man Ia as liable to infectious diseases
q pauper, while diphtheria, Group whoopng cough
and scarlet fever are more prevalent among the
rich Consumption and pneumonia claim the poor,
who are comparatively free from brain fever Gel
lar dwellers are far more subject to disease than
those who live above ground, except in diphtheria
and scarlet fever; nor do these diseases seem
greatly advanced by overcrowding in tenements
The greatest gunpowder blast ir connection
with railway works was that by which Sir William
Cubtt blew away with one charge of Is, 600 pounds
Cliff which 10 the hight of $50 feet above the
level of the sea- within few miles of Dover. This
monster blast fired by electricity at several points
at once, tore from the cliffs mass of more than
million tons of chalk.
An Englishman with simple device for taking
the terrors out of an earthquake is travelling in
Japan explaining his plan to the natives. They
have built their houses for many years with the
superstructure unfastened to the foundation, and
found that in some cases the earths tremors Were
not transmitted above the solid work. The English
says that handful of cast iron pellets scatter
ed on each OF the main supports of the house will
still further interfere with the transmission and
duce the amount of disturbance to about one-tenth
of that of the ground.
The Paris Gaulois Is authority for the state
ment that changeable chart has just been invented
for the of railroads. which viii do away COM
petely with danger from collisions. 1t consists of
sheet of opaque glass in which the rails indi-
Gated by horizontal lines and the stations by Vert-
cal lines numbered. Little arrows representing the
trains move along the horizontal lines and allow
the operator to see every movement on the section
he controls. If one train gets dangerously near
another he signal it at once, and the engineer
can take whatever precautions are necessary. The
whole apparatus is worked by electricity and the
arrows put in motion by the contact of metallic
brushes attached to the locomotive with zinc bands
placed along the rails.
Some curious experiments were made on the
decapitated head of Gagny, a murderer, executed
recently at Troyes, France, Is minutes after its
separation from the trunk. The blood of dog was
infused through the carotid artery, and by titla-
ting the nerves the eyeids became contracted, and
movements were visible in the lower jaw.