পাতা:পদার্থবিদ্যাসার.djvu/১৮৫

ASA SSASAS SSAS S S S S S S 174 Tut, By the Persians it is used internally as a cordial. In some places, it is burned in lamps instead of oil. When mixed with oertain other oils, it forms an excellent varnish. Pup. For what is coal nsed ? Tut. Principally for burning, or making fires: it is an article of great consumption in northern climates : and is so important to the inhabitants of these clines, that without it they could not cook their victuals, nor carry on thany mechanical works, now pass their winter evening with confort, I'up. Łs resin of any particular value * Tut. Some resins are ; as the aimber, which is well known, and extensively used, in different parts of the world. Pup. Have the goodness wow to tell uie something of the fourth class of imnerals, the metals. How inany orders of metals are there * Tut. Metals are divided into two orders, cali, d the malleable and brittle. Pup. What are the malleable metais? Tut. They are those which can be extended by means of the hammer, without breaking. Of this kind are gold, platina, silver, copper, iron, tin, and lead. Pup. Which is the most useful of these metals Tut. Iron. Gold ulay purchase iron, but it cannot serve as a substitute for it, because it is not equaliy hard. Gold would not serve for ploughs or anchors. In a word, not any thing you have about you is made without the assistance of iron, in one shape or another. Pup. What are the brittle metals?