Page:Philosophical Transactions - Volume 095.djvu/49

Rh globules. No. 1 of silver, diameter ,01137; No. 2 of sealing-wax ,01125; No. 3 of pitch ,00653.

With 522,7 I saw No. 1 round, and could estimate $1⁄4$ of its diameter. The angle is 0"989; $1⁄4$ of it is 0",247.

I saw No. 2 round, but of a dusky-red colour. It is not nearly so bright as No. 1; nor does it appear quite so large as the proportional measure of the globules would require. I can estimate $1⁄3$ of its diameter. The angle is 0",979; and $1⁄3$ of it is 0",326.

No 3 reflects so little light that I can barely perceive the globule, but not its form; and yet it subtends an angle of 0",568.

To discover whether this ought to be ascribed intirely to the want of reflection of the pitch, I took up some white melted bee's-wax, by dipping the fine point of a needle perpendicularly into it. This happened to be only half a globule, and its diameter was ,0105.

When I examined the object with 523 I saw it with great ease, and could estimate $1⁄4$ of its diameter. The angle is 0",914; and $1⁄4$ of it is 0",228. I saw also that it was but half a globule.

I took up another, that I might have a round one; but found that again I had only half a globule. It was so perfectly bisected, that art and care united could not have done it better. Its diameter was ,0108. In the telescope I saw its semiglobular form, and could estimate $1⁄4$ of its diameter.

By some further trials it appeared, that a perfect globule of this substance could not be taken up, the reason of which it is not difficult to perceive; for as it melts with very little heat, it will cool the moment the needle is lifted up; and the surface, which cools first, will be flat.