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120 taking it from one substance and bringing it to other matters. I cannot make a piece of iron or anything else heavier or lighter than it is; its cohesive power it must and does have; but, as you have seen by these experiments, we can add or subtract this power of magnetism, and almost do as we like with it.

And now we will return for a short time to the subject treated of at the commencement of this lecture.

You see here (fig. 41) a large machine arranged for the purpose of rubbing glass with silk, and for obtaining the power called electricity; and the moment the handle