METALS. 197 



made ? 263. What materials are used to color glass ? 264. How is 

 ing done, and with what object ? Describe the experiment with Prince Bu- 

 pert's Drops. 265. What is slag ? Why do oyster-shells remove clinker in 

 a furnace ? 266. What is said of soluble glass ? 267. Of what is earthen- 

 ware made ? Whence comes the reddish color of bricks ? Why did the 

 Egyptians use straw in making bricks ? 268. How is glazing done ? How 

 are finer articles glazed ? 269. What is said of the occurrence of boracic 

 acid? What is borax? 



CHAPTER XV. 



METALS. 



270. Characteristics of the Metals. Metals as a class of 

 substances have certain general characteristics. 1. In masses 

 they are opaque bodies. It has been thought by some that 

 gold is an exception, for they assert that light is transmitted 

 through it when made into lea.even when the leaf is not 

 so thin as to permit transmission through multitudes of lit- 

 tle openings. 2. Metals are not soluble. It is commonly 

 stated that they are not soluble in water. But it may be 

 said with truth that they are not soluble in any liquid ;* for, 

 as you will see farther on in this book, in those cases in 

 which metals are spoken of as being dissolved, it is not 

 really the metal which dissolves, but a chemical compound 

 is formed with the metal by the liquid, and then this com- 

 pound is dissolved. 3. Metals have more or less of a certain 

 brilliancy, which is termed, whenever it is found in other 

 substances, the metallic lustre. 4. Metals are better con- 

 ductors of heat and electricity than the non- metals, -and 

 most of them have a higher specific gravity. 



Some of the properties of metals require a closer examina- 



Certain TymaA^Kte rnqgs excepted. 



