subsequently to the interior ones, so as to protect a coast
hitherto exposed, or that overwhelming deluges had swept
down the valleys, and in some manner produced, in one day,
the effects of attrition which on ordinary occasions require
the prolonged action of centuries.
If we could at the present day submerge the greater part
of Tierra del Fuego, or leave unelevated that which we know
has recently been gained, an island with a few small outliers
would be formed, similar to Georgia, and situated in
exactly the same latitude. Have we in such case the slightest
right to deny the probability that the snow-line would descend
nearly to the wateFs edge, and that every valley
would be “ terminated by a wall of ice,” and that “ in winter
masses would be broken off a n d dispersed over the sea?”—all
of which circumstances are now happening in Georgia. The
currents, which always set from the westward towards the
east, would drift these floating masses through the channels
towards the eastern side. And as we know that icebergs at
the present day, in both hemispheres, occasionally transport
fragments of rock, so we cannot deny that those of Tierra del
Fuego might formerly have done so. AA'hen the land was
elevated, the fragments of rock would be found deposited on
the eastern side of the continent, in bands representing the
ancient channels. AA’hether or not the hypothesis of their
transport be true, such is the position of the erratic blocks
in Tierra del Fuego.
AATth respect to the general theory of the transport by
great fragments of ice, especially of such as are angular, I
may add a few remarks. Humboldt having observed that
none occurred over the vast intertropical plains of the eastern
side of South America, believed that they were entirely
absent from the whole continent. As far as I am able to
discover from the works of travellers, and from what I have
myself seen, the remark holds good in the countries on both
sides of the Cordillera as far south as central Chile. Azara has
particularly stated such to be the case in Chaco. AVith
respect to the tributaries of tho Amazons, nothing can more
strongly prove it than La Condamine’s* story. He says,
“ Below Borja even for four or five hundred leagues, a stone,
even a single flint, is as great a rarity as a diamond would
be. The savages of those countries don’t know what a stone
is, and have not even a notion of it. It is diversion enough
to see some of them when they come to Borja, and first meet
with stones, express their admiration at them with signs, and
be eager to pick them up, loading themselves therewith as
with a valuable merchandise.” It is therefore a remarkable
circumstance that as soon as we reach the colder latitudes in
the southern hemisphere (from 41° to Cape Horn), the same
phenomenon occurs, almost on as grand a scale and with
similar limits, as in the northern parts both of the Old and
New AVorld. Neither in the southern nor in the northern
hemisphere do the fragments, coming from the polar regions,
or from other mountain groups, arrive within a considerable
distance of the lines of the tropics.
AVe must couple the absence of erratic blocks along that
part of the Andes which is situated under a warmer climate,
with the similar non-occurrence, as I am informed by Professor
Royle, in Northern India round the flanks of the
Himmalaya;—those loftiest pinnacles on the face of the globe.
AA^ith regard to Southern Africa, from lat. 35° to the tropic.
Dr. Andrew Smith, who has visited as a naturalist so large a
portion of the interior, assures me he has never seen any
thing of the kind. Nor do I recollect meeting with any
mention of them, in the works of the numerous travellers in
the equatorial regions of the same continent. The same
remark certainly holds good with Australia in the parallel of
Sydney, but perhaps is more doubtful with respect to Van
Diemen’s Land.f To my mind these negative factsf have
* L a G o n d am in e ’s Vo y ag e (E n g lis h tra n s la tio n ) , p . 2 4 .
■f I w ill h e r e p u t to g e th e r a ll th e ( a p p a r e n t? ) e x c e p tio n s w h ic h I h av e
m e t w ith to th e s u p p o s e d law t h a t e r r a tic b lo ck s a r e a b s e n t in th e in te r tro
p ic a l reg io n s o f th e w o rld . F ir s t, in th e B u lle tin d e l a S o c ié té ( ié o -
lo g iq u c , 1837, p . 2 34, th e r e is a n a c c o u n t o f som e e r r a tic b lo c k s n e a r
M acao ( la t. 2 2 ° N .) ; b u t a s i t is d is tin c tly s ta te d th e y a r e a ll o f g r a n ite ,
VOL. i n . u
h I