Bradford opinion. [volume] (Bradford, Vt.) 1874-1881, 1876-12-09
GROWTH OF THE EARTH.


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"Since meteoric matter IL continually
falling upon the earth, she must OF
course be growing larger, and the daily
number OF meteors is so immense that
it would be natural to suppose that the
increase might be quite appreciable in
few centuries. II is not no, however,
the surface Of the earth is so enormous,
compared with the quantity Of meteoric
matter, that, even on the most favorable
hypothesos, her diameter would grow
only about an inch in tive hundred mil,
lion years by accessions OF this kind. A
few figures will make this clear. "'' '''
GAS to the number OF Visible metoors,
there is substantial agreement among
authorities. The estimate of Professor
Newton is as large as that Of any one, !
believe, and he puts it at 600, 900 per
diem, which number, we will use. Az
to their average weight there ia more
difference of opinion. Probably, how
ever, the most careful and best founded
investigation is that Of Professor Hark-
ness, published in his report upon OBJ.
servation of tho November meteOrs OF
1866; and bis conclusion is that the
mass of ordinary shooting stars does not
differ greatly from one grain Profess
sor Nowcomb appears also to concur IN
this estimate. There are reasons. which
it would take too long to discuss, for
thinking that this value is likely to be
somewhat too small but on the other
hand it is almost absolutely certain that
the average mass cannot be RS great as
one-fourth of an ounce. 10 be on the
safe side, we will assume one hundred
grains as the mean weight of the visible
shooting stars.
Remembering that tue pound is
1000 grains, we. shall then find nearly
107, 900 pounds, or about fifty tons, for
the total weight of one days supply OF
shooting stars. An allowance must
also be made for the meteors too small
to be visible (Which are known by teles-
copic observations to be very numer-
QUE, and for tho matter brought down
by aerolites. Il we double the quantity
stated above we shall certainly he abun-
dainty liberal, and this will give us 214,-
coo pounds a day, or about 78, 1854, 600
pounds per year, rs tho eartll's rate OF
growth in weight. . .., .E
''Her increase of bulk depends upon
the density OF the meteoric matter, and
probably this density does not differ
much from that of ordinary soil, or
nearly three times that of water. Ii 80,
each cubic foot would weigh about 1874
pounds, and the annual meteoric access
sion to the bulk of the earth would be
not far from All, 900 cubic feet. A cube
about seventy five feet on each side
would be q little larger. 1t would take
more than four millions such to make q
pile as large as Mount Washington.
Now, since the surface of the earth is
about 5,484 millions of millions OF
square feet, it follows that the annual
supply of meteoric matter, if spread
uniformly, would form layer whose
thickness would be only 1-13, 155, 600, 600
a foot, or very nearly IL, 100, 600, 900 Of i
an inch. In other words, even on such q
extravagantly favorable hypotheses as
we have assumed, the formation OF o
earth to a depth of one inch would re-
quire period of eleven hundred mil
lions of years.
eff we suppose meteorio matter to f.
have been just as abundant in space rs
now, since the beginning of time. and
that the velocity of the earth's orbital
motion has remained unchanged, and
that tho effects of her atmosphere and
Of her gradual shrinkage under the ac-
tioa of gravity can be neglected, then it
can be shown by an easy course Of rea-
soning, which would, however, hardly
suit these columns, that her diameter
must have grown during her whole ex-
stence at the same uniform rate as now,
md we find that to build her up to her
present dimensions by such process of
aggregation must have taken period of
1t least twenty-seven and a half millions
of millions of years.
"It is not intended to assert, however,,
hat the earth was really formed in this
way and even if it was, the above esti-
nate is of little value except as indi-
,ating the order of magnitude involved;
ince there is no certainty whatever
lot even probability-that in the early
tages of the formation Of the planetary
ystem circumstances nearly enough re-
embed the present to warrant any con-
usion. Nor must it be forgotten that ''
he probable estimates OF Hardness and
thers as to the weight of metoors would
ongthen all the periods of time mem
ioned from ten to one hundred fold.
We have given the smallest values pos
ihle."