Of the Attra&ion of Magnetism. 47

Observations of Mr. Pound, which is inserted at theEnd of the Lecture on Wind and Sound.

ix. I think the Law of Magnetic Attraction is notyet ascertained ; Sir Isaac Newton supposes it to decreasenearly in the Triplicate Ratio of the Distance : But Dr.Heljham, trying the Experiment with his Loadstone,found it to be as the Squares of the Distances inversely.And the Power of my Loadstone decreases in a differentManner from either, it being in the Sesquiplicate R.tioof the Distances inversely. For Exactness, I made asquare Bar of Iron just * of an Inch thick, and thenprovided three Pieces of Wood of the fame Form andThickness precisely. Then poising the Loadstone verynicely at the End of a Balance which would turn withless than a Grain, I placed under it the Iron with firstone Piece of Wood, then two Pieces, and lastly allthree Pieces upon it, by which means the Steel Pointsof the Pole were kept at j, -C, 3 of an Inch from theIron, and in those Distances the Weights put into theopposite Scale to raise the Loadstone from the Wood(which it touch’d while the Beam was horizontal) wereas follows:

Ratio os Ratio of Sesquip.

Grains, the Squares, the Cubes. Ratio.

tances

12. Whence it appears, that the Numbers of Grains

to counter-act the Power of the Loadstone in these Dis-tances approach very near, and are almost the famewith those which are in the Sesquiplicate Ratio, but arewidely different from those which are in the Duplicateor Triplicate Ratio ; and this Experiment I tried leveralTimes for each Distance, and with scarce any Variationin the S us cess.

13. The Power or Force of Magnets is generallygreater in small than in large ones, in Proportion totheir Bulk. It is very rare that very large ones will.take up more than 3 or 4 Times their own Weight,but a small one is but tolerably good that will takeup no more than 8, 10, or 12 Times its Weight. TheHonQurable Mr. Berkley , at Bruton, has or.e whose

Weight