The statement is sometimes made to the effect that coal is "condensed sunlight"; is it true, or untrue; and why? Why are the coal areas of Europe and America also areas of various manufactures? A recent cartoon had for its title--"John Bull and his coal piles (_i.e._, coaling stations) rule the world"; show why this statement contains a great deal of truth. What are some of the advantages of steam-vessels over sailing-vessels? Whale oil, crude turpentine, kerosene, and gas have been used each in turn for illuminants; what is the advantage of each over the preceding? Describe the structure of an ordinary kerosene lamp-burner, an argand burner, a Welsbach burner. For what are aniline, paraffine, naphtha, and carbolic acid used? FOR STUDY AND REFERENCE Obtain specimens of anthracite, bituminous, and cannel coal, and coke for comparison and study. Obtain specimens of crude petroleum, naphtha, refined oil, aniline dye, paraffine, and carbolic acid; note the properties of each. Throw away the naphtha after using. Read Mineral Resources of the United States on the foregoing subjects. CHAPTER XIII METALS OF THE ARTS AND SCIENCES The development of modern civilization is directly connected with the mining and manufacture of the useful metals. Their effect on the affairs of mankind can be rightly understood only when they are studied in their relations to one another, as well as to the people who used them. Next to the discovery of the use of fire, an appreciation of the use of metals has been the chief thing to develop the intellect of mankind. When human beings discarded natural caves for artificially constructed dwellings--when they began to cook their food and clothe their bodies, they required tools. These, in the main, consisted of the spears and arrow-heads used as weapons of the chase, and the axes and knives used as constructive tools. Rough stone gave place to flint because the latter would take a better edge. For the same reason the people of central Europe sent to the deserts of central Asia for jade wherewith to make axes and knives. Again, for the same reason, jade was discarded, because an alloy of copper and tin produced a bronze that would not only take a sharper edge than stone, but it was hard enough to cut and dress the latter. Egypt rose to a commanding position because of her control of the copper mines in the Sinaitic peninsula, and subsequently of the gold products coming from the upper Nile.