270 DISCOURSE ON THE STUDY 



fusible, and incapable even of agglutination by heat. 

 To this he replied, that the pressure under which 

 the heat was applied would prevent the escape of 

 the carbonic acid ; and that being retained, it might 

 be expected to give that fusibility to the compound 

 which the simple quicklime wanted. The next 

 generation saw this anticipation converted into an 

 observed fact, and verified by the direct experiments 

 of Sir James Hall, who actually succeeded in melt- 

 ing marble, by retaining its carbonic acid under 

 violent pressure. 



(300.) Kepler, among a number of vague and 

 even wild speculations on the causes of the motions 

 whoso laws he had developed so beautifully and 

 with so much patient labour, had obtained a glimpse 

 of the general law of the inertia of matter, as ap- 

 plicable to the great masses of the heavenly bodies 

 as well as to those with which we are conversant 

 on the earth. After Kepler, Galileo, while he gave 

 the finishing blow to the Aristotelian dogmas which 

 erected a barrier between the laws of celestial and 

 terrestrial motion, by his powerful argument and 

 caustic ridicule, contributed, by his investigations 

 of the laws of falling bodies and the motions of pro- 

 jectiles, to lay the foundation of a true system of 

 dynamics, by which motions could be determined 

 from a knowledge of the forces producing them, 

 and forces from the motions they produce. Hooke 

 went yet farther, and obtained a view so distinct of 

 the mode in which the planets might be retained 

 in their orbits by the sun's attraction, that, had his 

 mathematical attainments been equal to his philo- 

 sophical acumen, and his scientific pursuits been 



