CENTURY VIII. 



and therefore needeth more force to be put in motion. 

 For if a weighty body be pensile, and hang but by 

 a thread, the percussion will make an impulsion 

 very near as easily as if it were already in motion. 



764. A body over-great or over-small, will not be 

 thrown so far as a body of a middle size : so that, it 

 seemeth there must be a commensuration, or pro 

 portion between the body moved and the force, to 

 make it move well. The cause is, because to the 

 impulsion there is requisite the force of the body that 

 moveth, and the resistance of the body that is moved : 

 and if the body be too great, it yieldeth too little ; 

 and if it be too small, it resisteth too little. 



765. It is common experience, that no weight will 

 press or cut so strong, being laid upon a body, as 

 falling or strucken from above. It may be the air hath 

 some part in furthering the percussion ; but the chief 

 cause I take to be, for that the parts of the body moved 

 have by impulsion, or by the motion of gravity con 

 tinued, a compression in them, as well downwards, 

 as they have when they are thrown, or shot through 

 the air, forwards. I conceive also, that the quick 

 loose of that motion preventeth the resistance of the 

 body below : and the priority of the force always is of 

 great efficacy, as appeareth in infinite instances. 



Experiment solitary touching titillation. 



766. Tickling is most in the soles of the feet, and 



under the arm-holes, and 6n the sides. The cause is 



the thinness of the skin in those parts, joined with the 



rareness of being touched there : for all tickling is a 



