Page:On the various forces of nature and their relations to each other.djvu/54

may consider these then as separate particles magnified, so as to be evident to your sight; they are loose from each other—they all gravitate—they all fall to the earth—for the force of gravitation never fails. Now, I have here a centre of power which I will not name at present, and when these particles are placed upon it, see what an attraction they have for each other.

Here I have an arch of iron filings (fig. 12) Fig. 12.regularly built up like an iron bridge, because I have put them within a sphere of action which will cause them to attract each other. See!— I could let a mouse run through it, and yet if I try to do the same thing with them here [on