102 ESSAYS AND OBSERVATIONS 



preflions are always as the quantities of 

 matter, and fquares of the velocities con- 

 jointly J andconleqaently, when the quan- 

 tities of matter are equal, the impreffions 

 ■will be as the fquares of the velocities. 

 The fame experiment may be Ihewn per- 

 haps in a more fimple manner, by making 

 pendulums of different quantities of matter 

 to ftrike with different velocities upon ^ 

 fniooth furface of foft clay ; the velocities 

 being always afligned by help of a gradu- 

 ated arch, as is done in the common ex- 

 periments of the coUifion of bodies. In 

 this manner, likewife, the impreffions are 

 found to be equal, when the products of 

 the quantities of matter, by the fquares 

 of the velocities, are equal. Thus, let a 

 hollow ball, with a quantity of matter i, 

 move with a velocity 20, and make a cer- 

 tain impreflion. If you afterwards in-^ 

 clofe as much lead within the fame ball, 

 as to render it of double the mafs of mat- 

 ter, you muft give it a velocity fomewhat 

 exceeding 14, before it make an impref- 

 fion equal to the former one. If the bo- 



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