Page 201 - Third Book of Reading Lessons

200 THIRD BOOK OF
operates, it modi es, but does not destroy, the physi­ cal in uence. By xing the attention, then, on these ur ndamental truths, the student obtains, as it were, so many keys to unlock, and lights to illumine, the secrets and treasures of nature.
3. Every material mass in nature is divisible into very minute, indestructible, and unchangeable par­ ticles ;-as when a piece of any metal is bruised, broken, cut, dissolved, or otherwise trans rmed, a thousand times, but can always be exhibited again as
per ct as at rst. This truth is conveniently re­ called by giving to the particles the name a m, which is a Greek term, signifying that which cannot be. rther cut or divi ed, or an exceedingly minute resisting particle.
4. It is und that the atoms above re rred to, whether separate or already joined into masses, as when the atoms of which any mass is composed, are, by an invisible in uence, held together with a certain degree of rce; or when a bloqk of stone is similarly held down to the earth on which it lies; or when the tides on the earth rise towards the moon. These cts are conveniently recal d, by connecting with them the word attrac on, a drawing together, or gravi tion.
5. Atoms, under certain circumstances, as of heat di used among them, have their mutual attraction countervailed or resisted, and they tend to or sepa­ rate;-as when ice heated, melts into water; or when water heated, bursts into steam; or when gun­ powder ignited, explodes. Such cts are convenient­ ly called by the term repulsion, a thrusting asunder.
6. As a y-wheel made to revolve, at rst o ers resistance to the rce moving it, bnt gradually ac-