100 = Proofs of Currents upon the Earth's surface. 
found, except at the elbow joint, whatever fuel is employed, 
but [ am persuaded that a larger conducting tube than that 
which has been introduced in Philadelphia, would be advan- 
tageous, especially where there is any considerable extent of 
horizontal communication. ws gesie ee] 
I ought perhaps to add, that, at the close of the season, af 
ter the experience of more than six months, I find the collec- 
tion of light ashes. upon the sides and ceiling of the apart- 
ments, somewhat greater than I had supposed when the for- 
mer essay was writien, but there is no. serious imconvenience, 
as it is easily dusted away, and leaves very’ litile permanent 
effect. ras 
ty 
oo 9 
ArT. VIL. Proofs that general and powerful currents have 
h. a 
swept and worn the surface of the eart 
_. .. TO PROFESSOR SILLIMAN. 
RE is one circumstance connected with the earth’s sure 
face, which has not, that | am aware of, been noticed by any 
writer on Geology, The surface of every. portion of the mass 
of rock, composing nucleus of the earth, and which has 
been the action of the atmosphere, is found 
nin a very nearly north and south, but 
from a little west of north to » ete eo rica, sks 
This fact has appeared to me a very streking and important 
one, and it is a singular cireumstance that it should not have 
— by the numerous writers, who have carefully in- 
vestigated so’ many circumstances connected with the chang- 
og tes Si rt * 3 
