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7. Of (lie properties which we perceke by feeling, 

 the chief are moist ness 9 dryjiess, heat, and cold. There 

 is no heat without fire, or at least some disposition of 

 the heated body to take fire. If the particles of it, 

 rapidly agitated, strike against another body, tear and 

 dissolve it ; if against the body of a maji, the sensation 

 of heat arises in the mind. Some suppose cold consists 

 in the rest of those particles which were so agitated be- 

 fore. Others think this would not suffice to pruduce 

 that accule pain which we sometimes feel from cold ; 

 and 'therefore suppose there are positive frigorific par- 

 ticles, which move on in strait lines, and. so not only de- 

 stroy the circular motion which is required for heat, but 

 likewise penetrate the body, and sharply affect the ex- 

 tremities of the nerves. 



8. Gravity and levity have likewise been reckoned 

 among sensible qualities ; but properly, there is no such 

 a thing as levity, for all bodies tend to the centre of the 

 earth, though some are light in comparison of others, 

 The laws of gravity are, 1. All bodies on the earth tend 

 to a point which is (nearly at least) the centre of the 

 globe. 2. In all places equidistant from the centre/the 

 force of gravity is nearly equal. 3. Gravity equally 

 affects all bodies, without regard either to their bulk or 

 figure : so that were it not for the resistance of the me- 

 dium, the greatest and smallest bodies, the most dense- 

 arid the most rare, would descend equal spaces in equal 

 times. Thus gold and feathers descend alike in an ex- 

 hausted receiver. 4. This power increases as we de- 

 scend to the centre, and decreases as we ascend from 

 it, and that as the squares of the distances. Thus, at a 

 double distance, things have but a quarter of the force, 

 5. Those things swim in fluids which are specifically 

 (that is bulk for bulk) lighter than those fluids. 



This gravitating power seems to be congenial to 

 matter: it penetrates even to the centre of the sun and 

 other heavenly bodies, without any diminution of its 

 virtue ; and it acts not according to the surface of 

 bodies, as mechanical causes do, but according to the 

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