Year: 1860

, the force thus apparently destroyed is con
verted into heat. We're the earth, which
, moves at the rate Of about nineteen miles Del
second to be suddenly brought to rest, by
: striking an immOvable obstacle the heat gen.
Grated would be equal to that which would bt
| produced by the instant and complete com.
buSton Of nearly eighteen times its Owr
weight Of coal, and would raise the tempera.
ture of the whole mass to point about five
hundred times hotter than that Of the hottest
wind-iurnace, and more than six hundred
times hotter than melted iron as it flows from
a smelling furnace.


Were body to fall from the point of equi-
llbrlum between the earth and moon, it would
enter the atmosphere with velocity only
about a third as great as that of the earth in
its orbit, and as the forces represented by mo-
wing masses are as great as the squares of the
Velocltles, Its eat-producing power would be
but one ninth as great Were such body
to be suddenly arrested, its temperature
y ellssl 30 Faises on zeSL4tg times that
OF melted IRON; a''+ were it only to be retari-
ed' 1t Wonld become heated in proportion to
the retardation.


The actual retardation of BODY moving
through the air will vary with the magnitude
and density of the mass; but a small body





average density of meteoric stones-thoueh
falling vertically downward, and therefore
constantly urged by gravity, and though en-
tenng the air with the velocity of six and
| one half miles, acquired in falling from the
moon, would soon be reduced to the uniform
velocity Of quarter of mile per second
What the actual velocity of meteoric bodies
! is, it is difficult to determine. They are seen
q ia L. fhn,
by practlsed observers, and those who see
them are usually so taken by surprise. that
the statements made by them as to duration
and direction and length Of track. are often
very dlscordant. But whatever it NAV he
there is no sort Of doubt that it must he very
senslbly reduced during their flight through
the atmosphere and the reduction will he
most considerable in given time, In the case
of those whose original velocities are highest.
DR.. Bowd:tch estimated the velocity of the
Weston meteor (Connecticut) in 1907 at
three miles an hour. Mr.. Herrick deduces
three miles and hall from the reported OBJ
seryauons; but expresses his belief that the
observers made the duration at least three
times too great, and consequently that the
velocity must have been at least ten miles
per hour. These, of course, are the estimat-
ed velocitles during the period of the visibili-
ty of the meteor, but the body could not have
become visible until after being highly heated;
and therefore the initial velocity can only be |
conjectured.


Ii DIR. Bowdltch'S estimate is correct for the |
Weston meteor, and if the original velocity |
had been that acquired by falling from the |
point of equilibrium between the earth |
and moon, then there must have been a |
reduction of more than half the original
velocity, and therefore of more than three
quarters of the force; or in other words, there
must have been generation Of heat sufficient
to elevate the temperature Of the body to a
point nearly fifty times above the heat of
melted IRON. This suppOSes the conversion |
OF the entire force lost into heat. conside-
rable portion of it is however merely trans
lerred to the portions of the air which the |
meteor sets in motion; and another portion is |
expended in raising the temperature of the |
same air. Making every abatement demand
ed by these considerations, and allowing also.
that the actual retardation owing to the rarity
of the upper air, may be much less than as
sumed above, there still remains an abund-
antly satisfactory explanation of the luminos-
ity, the explosion, and the fusion and vitrifac-
ton of these bodies; while the greater heat
at the surface than in the interior is account
ed for by the fact that the resisting force is
applied directly at the surface.


have thus cadeavofel to answer your in
quiries as briefly as the nature of the subject
would permit If have told you little which
you did not knew before, it must he attribut-
ed to the fact that science has really, upon
this subject, so little to tell.


| am, sir, respectfully, etc,


f. a. ?. BARNARD.