133 



size: so did diamonds also. And a very small piece of 

 tempered steel broke all the glasses into \vhich I 

 dropped it." 



Some large hollow cups made at Worcester, of common 

 green glass, much larger than the others, and some of 

 them above three inches thick at the bottom, though 

 they were not affected by a musket-ball, dropt from the 

 height of near three feet, were instantly broken with a 

 shiver of flint, weighing but two grains. 



There is something astonishing in the power of tele- 

 scopes to bring far distant objects near ; and of micro- 

 scopes, to render those clear and distinct, which are 

 quite invisible to the naked eye. And no less amazing 

 in another kind is the force of burning glasses. 1. A 

 piece of wood laid before a large burning glass, took 

 iire in an instant. 2. Water contained in an earthen 

 vessel boiled immediately, and in a short time quite 

 evaporated. 3. A mass of lead, three inches thick, 

 began to melt in a moment, and soon after ran in a con- 

 tinued thread. 4. A steel plate grew red hot almost in 

 an instant, and small holes were made through it. 

 5. Slate becomes black glass; tiles, yellow glass; 

 earthen pots, a darkish yellow glass. 6. A pumice 

 stone became white glass; earth, black glass; bones au 

 opake one. 



But in the extremely hot weather at Paris, in 1705, 

 the rays of the sun, collected by a large glass, had scarce 

 any force, though the separate rays quite inflamed the 

 air. The reason of so surprising a thing seems to be, 

 that the heat raised from the earth's great sulphureous 

 exhalations, embarrassed, stopped, and in some degiee 

 absorbed the rays of the sun. 



29. Equally strange are the phenomena of the glass- 

 drop. The make of this drop is as simple as its expla- 

 nation is difficult. They take up a small quantity of 

 melted glass on the top of an iron rod, and let it drop 

 into a pail of water. When it does not break in the 

 operation, it forms the glass-drop. This is of such 

 firmness, that it bears smart blows of a hammer, without 

 G '6 



