G'b 
JRemarks on the blowing up op Mi^ks 
Cincinnati Heading-room, Oct. Hth * 
My friend. Doctor Mitchill, in l«« third 
letter to me, published on the 9 thrinstant, 
seems to suppose (with many others) tha 
I describe or consider the spheres as com¬ 
pact earth and water quite through; where- 
L, I have undertaken to demonstrate that 
they are very hollow,—containing not, 
only a mid-plane cavity of wide and deep 
extent, filled with hydrogen and other 
very rare gases, (such as escape and con¬ 
dense into, liquid fire and lava at the great 
volcanos,) but that between such mtd- 
olane space or cavity, and either surface, 
numerous other intermediate lesser cavi¬ 
ties exist in a similar manner, lessoning, 
in extent and depth by intermediate de| 
grees, towards both the inner and outer? 
surface of the sphere ; so that, if it were 
practicable to dig down to the mid-plane 
or volcanic cavity, the confined air would 
escape (at least at some seasons,) and a 
sort of volcanic eruption be produced. 
However on only digging to one of the first 
intermediate cavities, our progress would 
be stopped by the escape of confined gas 
protruding from such cavity—hence a 
temporary, or pseudo volcano, would be 
formed which would or should, according 
to my theory, continue open,until so much 
gas, or confined air, might escape, as to let 
ifie .incumbent stratum or shell settle 
down in contact with the one next below. 
In such case, the digging.could again be 
prosecuted, but with great danger; for, 
should any convulsion or earthquake oc¬ 
cur, so as to force the confined air along 
such cavity,—‘■towards where the shaft pas¬ 
sed through it,—-with a sufficient protru¬ 
sive'force to again elevate the incumbent ' 
strata or stratum, the consequence would 
be fatal to the workmen; tor the rarity of 
such volcanic air would be so great, as to 
cause it to suddenly condense, on rising 
to where the superior gravity of the outer 
surface, and the incumbent weight of the 
atmosphere, acted on it: hence much lat¬ 
ent heat would be set free by such conden¬ 
sation, so as not only to unfit it for 
