- fire-brick sing of such furnaces is only from 44 to 9 inches thick, and 
_ its present form, has been covered by the creation which now occupies 
: Scientific inuétligence 
ee f 
§ % * 
This half- inch. thickness of mineral substance, however, was quite 
7 is ‘ient to roo the conduction of the heat to the exterior so com- 
0 
3 
a, 
[=* 
bod 
f=) 
a 
jt a 
5 
2 
5 
Bh 
“3 
® 
| al 
so slowly and imperfectly does this thin li- 
ning of half an inch of a and sand permit the heat to pass outwards, 
that the entire mass night rest there till it became cool ere the outside. 
‘of the pot would have reached a temperature high enough to carbonize 
wood in contact with it, the radiation from the ‘outside carrying away 
the heat as fast as the slow conducting power of the clay and sand li- 
ning spe it. 
So strikin ng an instance of the low conducting power of such sub- 
stances is not frequently met with, and it appea 3 10 me that it is caleu- 
lated to remove some of the doubts yeh expres ee 
facts ee indicate a high temperature in the interior of the ear rth. If, 
half an inch of mineral matter thus intercepts the ise of so 
of high heat, the only ee of which, at the tae are afford ded. 
by volcanos, hot springs, and that regular increase of temperature € as WO 
Me 
yet while the heat within is as high as our eee powers will carry abs 
the hand aay be placed natelds without suffering any inconvenience, ~ 
3. On the Changes of the Vegetable Kingdom in the different Geolog- - 
ical Epochs ;. by M. Avo.pn s Bronentarr, (Edin. New Phil. Jouty* 
Jan. 1848 ; from L’Institut, ees 714, p. 280. )—The. changes which o. ie. 
taken place in the nature of living beings, since their first appear | 
on the globe till the period when the surface of the earth, having ae "a | 
— = 
it, constitutes one of the most interesting sonia of geology : : As has 
the history of life and its metamorphos . 
e fad ogress of re geology present s to us the surface. fe the , 
globe becoming renewed many times since the period when life 
appeared aint it, under Shes influence of Creative Power. At each of 
hese modifications—every time that a great bed of mineral matter cov- ’ 
the living beings which inhabited a earth, oaaya and bu uried in” 
these sedimentary deposits, were replaced by 8 new creatio more or 
less different from the preceding. 
