124i Hints for the Formation of 
2. The figure and dimensions of the earth determined, 
3. The density of the earth determined by the devia- 
tion of a plummet near some mountains, the dimensions 
and density of which are known. 
4. Whether any principles or hypotheses, depending 
on astronomical geography, can explain the great changes 
in the temperature of some parts of our globe ? 
5. The courses of comets. Whether it be possible 
that they may have met with, or still meet with, the 
earth in their orbits, and what are the effects of such a 
meeting ? 
6. Whether it be possible, I do not say probable, that 
a comet, by passing through part of the sun, may have 
detached from it the earth and the other planets ? 
7. Is it probable that the earth’s rotary motion has 
been formerly more rapid than it is at present ? 
8. If the grand chains of mountains existed before 
the rotary motion of the earth, is it possible that that mo- 
tion produced any change in their original situation ?* 
CHAP. II. 
Chemical and Physical Principles . 
1. The theory of attraction and chemical affinities ; of 
solution, crystallisation, and precipitation. 
2. The theory of elastic fluids in general, and the 
cause of their elasticity.! 
3. The theory of caloric and light ; of the origin and 
nature of the different gases, and of the atmosphere. 
Electricity, and the aurora borealis. 
4. The theory of the calcination of metals, and of the 
decomposition of water. 
5. Measuring heights by the barometer. 
* Tableau des Etats Unis. Note of M. A. Pictet, p. 125, 
f System of M. Le Sage. 
