292 
one case, why not in the other? With a 
native food-plant (Maclura aurantiaca) now 
known to be available over most of our domain, 
with a rapidly-increasing population, with in- 
creasing means of communication, and with 
the settlement of sections of the country that 
by climate are pre-eminently adapted to silk- 
culture, the present period has advantages for 
this culture possessed at no other period, and 
the question is pertinent. We do not propose 
to introduce a homily on free trade; but we 
think that the chief answer that can be given 
to the question is, that our silk-manufactures 
are established, and give employment to a large 
number of operatives, while silk-culture as an 
industry amounts to so little that there is 
nothing to protect. The same could have been 
said of silk-manufacture while it was struggling 
for establishment, and means little more than 
that we must keep up a discriminating policy, 
simply because we have begun it ; and the more 
powerful and wealthy the manufacturing inter- 
est becomes, the more certain will it be kept up. 
This is the secret, in a nutshell, of the failure of 
silk-culture at the present time ; and the pros- 
pect for what might otherwise become a valu- 
able productive industry is certainly gloomy. 
SCRIBNER’S WHERE DID LIFE BEGIN? 
Where did life begin? a brief inquiry as to the proba- 
ble place of beginning and the natural courses of 
migration therefrom of the flora and fauna of the 
earth. By G. Hiirton Scripner. New York, 
Charles Scribner’s Sons, 1883. 6+64 p. 12°. 
Tuts little monograph is a full summary 
and straightforward statement of the principal 
grounds of the theory of the arctic origin of 
the plants and animals of the northern hemi- 
sphere. These grounds, in more condensed 
statement, are as follows: on any planet, or- 
ganic life would first appear in the region first 
suited for its reception. On a planet cooling 
from an incandescent state, the polar regions 
would first acquire a habitable temperature, 
both because their deficiency of solar heat 
would accelerate cooling, — that deficiency be- 
ing increased by polar flattening, which ren- 
ders the sun’s rays more oblique, and increases 
the radiating surface of the polar sides, — and 
because, underneath the polar sides, there is 
less matter to be cooled than underneath the 
equator. On our earth the polar regions are 
now too cold for life, and hence they have 
passed through the life-sustaining stage; and 
this was while more equatorial regions remained 
too hot. As the life-sustaining isothermals 
moved equatorially, animals and plants mi- 
SCIENCE. 
[Vou. IIL, No. 57. 
grated correspondingly. The progress of cli- 
matic change was not more favorable to this 
faunal and floral migration than were the south- 
ward bottom flow of water in the general oceanic 
circulation, and the general meridional trend of 
the continental and oceanic configuration, or 
the prevailing surface-movement in the atmos- 
pheric circulation. All these conditions oppose 
transmeridional migrations. Confirmatory of 
these deductions are numerous facts of observa- 
tion, —such as similarity of the fauna and flora 
at all parts of the same parallel of latitude ; 
the remains of tropical and subtropical animals 
and plants in arctic regions; the degenerate 
condition of certain arctic species, as whales, 
seals, and others; and the fundamental affini- 
ties of different tribes of plants and animals_ 
which testify to a common origin. 
Undoubtedly some of these considerations 
are entirely valid, and confer upon the theory 
a claim to sober consideration, not to mention 
the authority of names previously subscribed 
to it. What a hesitating believer would like 
to know further, is, whether the inferior polar 
radius of the earth would really accelerate or 
retard polar cooling, and whether the circula- 
tions of the sea and atmosphere have been such 
as to promote the migrations of plants and 
animals from high polar to equatorial latitudes. 
The deductions based on progress of planetary 
cooling are plausible: but the queries arise, 
whether circulations did not exist in the fluid 
planet before incrustation as well as in the 
fluids existing after incrustation ; and whether 
such circulation must not have maintained polar 
and equatorial surface temperatures so nearly 
equal as to permit nearly simultaneous incrusta- 
tion in all latitudes; and then, whether, after 
general incrustation, the crustal arrest of radia- 
tion must not have speedily diminished sub- 
crustal influence to such an extent that climate 
depended chiefly on solar radiation, since less 
than half a mile of crust would fail to conduct 
sufficient heat to affect surface temperature 
more than a small fraction of a degree. Then, 
on the side of inductive data, we have to con- 
sider whether the secular southward progress of 
identical climatic conditions would not be in- 
compatible with that continuity of sedimentary 
conditions, which, especially in North America, 
has been traced from the thirty-fifth to the 
sixty-fifth degree of latitude; and whether a 
similar progress of identical faunal conditions 
would not introduce a progressive change in 
the correlation of life to the age of the strata, 
leaving the same types in older strata north- 
ward, and newer strata southward, while obser- 
vation testifies that the same Hamilton types, 
0 
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