新书--世界学术经典·英文版:自然哲学的数学原理(精装)

Thus air of a double density,in a double space,is quadruple in quantity;in a triple space, sextuple in quantity.The same thing is tu be understood of snow,and fine dust or powders, that are condensed by compression or liquefaction,and of all bodies that are by any causes whatever differently condensed.I have no regard in this place to o medium,if any such there is, that freely pervades the interstices between the parts of bodies. It is this quantity that I mean hereafter everywhere under the name of body or mass. And the same is known by the weight of each body,for it is proportional to the weight, as I have found by experiments on pendulums,very accurately made, which shall be shown hereafter.