FORMATION‘ oF THe EARTH. 3 
centre and rife till they arrived at that region of the air 
which was of the fame fpecific gravity with themfelves, 
where they would reft; while other matter, mixed with 
the lighter air would ‘defcend, and the two meeting would 
form the fhell of the firft earth, leaving the upper atmof- 
phere nearly clear. The original movement of the parts 
towards their common centre, would naturally form a 
whirl there; which would continue in the turning of the 
new formed globe upon its axis, and the greateft diameter 
of the fhell would be in its equator. If by any accident 
afterwards the axis fhould be changed, the denfe internal 
fluid by altering its form muft burft the fhell and throw 
all its fubftance into the confufion in which we find it. 
I will not trouble you at prefent with my fancies con- 
cerning the manner of forming the reft of our fyftem. 
Superior beings {mile at our theories, and at our prefump- 
tion in making them. I will juft mention that your ob- 
fervation of the ferruginous nature of the lava which is 
thrown out from the depths oftour valcanos, gave me great 
pleafure. Ithas long beena fuppofition of mine that the 
iron contained in the fubftance of this globe, has made it 
capable of becoming as it is. a great magnet. That the 
fluid of magnetifm exifts perhaps in all fpace; fo that there 
isa magnetical North and South of the univerfe as well 
as of this globe, and that if it were poffible for a man to 
fly from ftar to flar, he might,govern his courfe by the 
compa{s.. That it was'by the power of this general mag- 
netifm this globe became-a particular magnet. In foft or 
hot iron the fluid of magnetifm is naturally diffufed equally; 
when within the influence of a magnet, it is drawn to one 
end of the iron, made denfer there, and rarer at the other, 
while the iron continues foft or hot, it is only a temporary 
magnet: If it cools or grows-hard in that fituation, it be- 
comes a permanent one, the magnetic fluid not eafily re- 
fuming its equilibrium. Perhaps it may be owing to the 
2 permanent 
