z o n e s, t h a t so lid g la c ie rs d e s c e n d to th e s e a in low la titu d e s ; I m ig h t h av e
a d d e d t h a t i t is in th is same h em isp h e re , t h a t th e ice b e rg s, w h ic h h a v e
b e e n fo rm e d in th e P o la r R e g io n s , a r e d r if te d fu r th e s t from th e i r b i r th p
la c e . H o r s b iirg h (Philosoph. Transact., 1 8 3 0 ) d e scrib es s e v e ra l g r e a t ice b
e rg s s e en b y a s h ip , in h e r p a ssag e to In d ia , in 3 5 ° 5 0 ' S . : t h a t is, f a r to
th e n o r thw a rd o f th e l a titu d e , w h e re tre e -f e rn s , a rb o r e s c e n t grasses, p a r a s
itic a l o rch id e o u s p la n ts , a n d e v e n p a lm - tr e e s g row ; a n d w ith in s ix ty mile s
o f th e lan d , w h e re th e rh in o c e ro s , e le p h a n t, h ip p o p o tam u s , l io n , a n d h y e n a ,
a re v e ry n um e ro u s .
P a g e 2 89.
U n t i l la te ly I was n o t aw a r e t h a t th e r e w e re su ffic ien t d a ta to sp e a k
w ith som e p re c is io n o f th e s o u th e r n lim its o f e r r a tic b lo ck s in th e n o r th e r n
h a lf o f th e N ew W o r ld . I n C a n a d a , a n d in th e n o r th e r n p a r t s o f th e
U n i t e d S ta te s , in n um e r a b le g r e a t s c a tte r e d fra gm e n ts o f ro ck s h a v e b e e n
d e s c rib ed b y Bayfie ld, B ig sly , H itc h c o c k , a n d o th e rs . I n p a r ts o f M a ssa c
h u s e tts , a c co rd in g to P ro fe s s o r H itc h c o c k ( Report on the Geology o f),
b o u ld e r s se em to c o v e r th e w h o le fac e o f th e c o u n try . F u r th e r s o u th w
a rd we h e a r f r om M r. R o g e rs {Report to Brit. Assoc., v o l. i ii .) t h a t b o u ld e rs
a r c com m o n o v e r th e g r e a t v a lle y w h ic h cro sses P e n n sy lv a n ia , M a ry la n d ,
a n d V irg in ia ( la t . 3G° 3 0 ' to 4 2 ° ) : a n d lik ew is e in th e s ta te s o f O h io ,
K e n tu c k y , a n d In d ia n a , w h ic h a r e in n e a rly th e s am e l a titu d e . M r.
R o g e rs h a v in g d e s c rib ed som e b lo ck s o f s a n d s to n e a t W a s h in g to n a n d o n
th e S u s q u e h a n n a , w h ic h m u s t h a v e com e from som e d is ta n c e n o r thw a rd ,
a d d s t h a t “ D r a k e in h is p ic tu r e o f C in c in n a ti (3 9 ° 10') m e n tio n s la rg e
masses o f g r a n ite in t h a t p a r t o f th e O h io , r e s tin g o n th e o rd in a ry fin e r
d ilu v ium . T h e n e a r e s t g r a n ite to th e n o r th is a t l e a s t o n e h u n d r e d lea g u e s
d i s t a n t ; w h ile n o p r im a ry ro c k o c c u rs s o u th o r e a st, w ith in ev en a m u ch
g r e a te r lim it.” H e th e n p ro c e e d s , “ W e a r e r em in d e d h e re o f th e g r e a t
d e ta c h e d b lo ck s , w h ic h s tr ew th e p la in s o f n o r th e rn E u ro p e , a n d th e e x p
la n a tio n su g g e ste d , t h a t th e y h a v e b e e n c a rr ie d th e r e u p o n flo a tin g ice
a n d c o n c lu d e s w ith th e im p o r ta n t r em a rk , th a t M r. C o n ra d , who h a s e x p
lo r e d th e s ta t e o f A la b am a ( 3 0 ° to 3 5 ° ) was n e v e r o n c e a b le to p e rc e iv e
a b o u ld e r u p o n its su rfa c e . I t w o u ld h e n c e a p p e a r th a t 3 6 ° 3 0 ' is th e
s o u th e rn l im it o f th e d isp e rs io n o f e r r a tic b lo ck s in th e U n i t e d S ta te s ;
a n d th e s e a r e s p o k e n of, a s h a v in g c om e from th e n o r th . T h e r e fo r e , th e r e
is n o o c c asio n to s u p p o s e t h a t th e ic e , in w h ic h b y th e th e o ry th e y a re
b e lie v e d to h a v e b e e n em b e d d e d , w a s fo rm e d in so low a l a t i tu d e as th a t
h e r e m e n tio n e d ; a n d a t p r e s e n t, in th e s o u th e rn h em isp h e re , iceb e rg s a r e
drifted to la titu d e s , th o u g h n o t fo rm e d in th em , n e a r e r th e tro p ic th a n
3 6 ° 3 0 '. I n E u r o p e I c a n n o t h e a r o f e r r a tic b lo ck s h a v in g b e e n fo u n d
f u r th e r s o u th th a n th e s o u th e r n fla n k s o f t h e A lp s , in la t. 4 5 ° ; a n d H um b
o ld t h a s sa id (se e Cuvier’s Theory o f the Earth, translated by Professor
Jameson, p . 3 4 6 ) t h a t th e y d o n o t o c c u r in L om b a rd y . I m ay h e r e r e m
a rk , th a t c a re s h o u ld b e t a k e n to s e p a r a te th e p h e n om e n o n o f g r e a t
angular b lo ck s , from th a t o f ro u n d e d o n e s , a lth o u g h o f c o n s id e ra b le
siz e ; fo r to r r e n ts , a n d m o re e sp e c ia lly th e wav e s o f th e se a , d u r in g
its s low o s c illa tio n o f le v e l, a r e a g e n ts su fficien tly p ow e rfu l to p ro d u c e
g r e a t effects. T h e low e s t l a t i tu d e in S o u th A m e ric a , in w h ich 1 fo u n d
la rg e a n g u la r f ra gm en ts , w h ic h m u s t h a v e b e e n t r a n s p o r t e d b y ice th e r e
fo rm ed , o r b y som e u n k n ow n m ean s, was in l a t i tu d e 4 1 ° , B u t as I d id
n o t e x am in e th e c o u n try im m e d ia te ly n o r th o f it, I am n o t p r e p a r e d to
s a y t h a t th is is th e i r e x tr em e lim it ; b u t b e tw e e n l a t i tu d e 2 7 ° a n d 3 3 ° , 1
fo u n d n o a p p e a r a n c e , o n e ith e r s id e o f th e C o rd ille ra , w h ic h in d ic a te d a
p ow e r o f t r a n s p o r ta tio n o f th e k in d r e q u ir e d to rem o v e b o u ld e r s from a
d is ta n c e . T h u s , w e fin d th a t th e lim it o f th e i r d isp e rs io n in th e tw o
A m e ric a s is n e a rly th e s am e ; a lth o u g h th e y a p p ro a c h th e w a rm e r zo n e s
r a th e r m o re c lo se ly in th e n o r th e rn tb a n in tb e s o u th e rn d iv isio n o f tlic
c o n tin e n t, a n d in b o th , p ro b a b ly , m o re so th a n in E u r o p e .
I n th e n o te , in w h ic h I h a v e c o n s id e r e d th e a p p a r e n t e x c e p tio n s to th e
law , t h a t e r r a tic b o u ld e r s a r e n o t fo u n d in th e in te r tr o p ic a l r eg io n s , I
h a v e s a id t h a t th e in te r n a l e v id e n c e o f t h e M a c a o case le d m e t o d o u b t its
r e a lity , a n d I n ow fin d i t is d is tin c tly s ta t e d b y M . C h e v a lie r t h a t th e
r o u n d e d b lo c k s r e s u lt from th e s e c u la r d is in te g r a tio n o f th e fu n d am e n ta l
ro c k (L T )is titu t,\% ^ S , p . 151— Analysis o f the Voyage o f the B o n ite ). I
m ay h e r e a d d , t h a t M . P u i llo n B o b la y e , in h is d e s c r ip tio n o f B o n e a n d
C o n s ta n tin e o n th e n o r th e r n c o a st o f A fr ic a (L T n s titu t, 1838, p . 2 4 8 ,
says, “ J e n ’a i rie n v u q u e p û t in d iq u e r le p h é n om è n e d e s b lo cs e r r a tiq u e s .”
M y s ta tem e n t t h a t e r r a tic b o u ld e r s a r e n o t fo u n d in A u s tr a lia , is fu lly
b o rn e o u t b y in fo rm a tio n c om m u n ic a te d to m e b y M a jo r M itc h e ll, w h o ,
in h is r e p e a te d e x p e d itio n s , h a s tra v e rs e d so m u c h o f th e s o u th - e a s t d iv is
io n o f t h a t c o n tin e n t. W i th th e s e v e ra l fac ts g iv en h e r e a n d in th e
J o u rn a l ( p . 2 8 9 ), I c a n s c arc e ly d o u b t t h a t th e law o f th e d is tr ib u tio n o f
e r r a tic b lo ck s is fin a lly d e te rm in e d ; a n d i t is n e e d le s s to s p e c ify th e great>
n o t to say c o n c lu s iv e , im p o r ta n c e o f th is law o n th e th e o r y o f th e m e a n s
o f t h e i r t r a n s p o r ta tio n , — a p ro b lem w h ic h h a s so lo n g p e rp le x e d
g eo lo g ists.
P a g e 2 9 4 .
I n m y d iscu s s io n o n th e c lim a te o f th e s o u th e r n h em is p h e re , I h a v e
sh ow n th a t a low a lt i tu d e o f th e lin e o f p e rp e tu a l sn ow, a n d c o n s e q u e n tly
tb e d e s c e n t o f g lac ie rs to th e le v e l o f th e s e a in la titu d e s r e la tiv e ly low to
w h a t o c c u rs in th e n o r th e r n h em is p h e re , a n d lik ew ise th e p e rp e tu a l c o n g
e la tio n o f th e s o il a l it tl e b e n e a th th e su rfa c e in c o u n tr ie s w i th o u t th e