In this chapter a series of six consecutive weather maps is taken as the basis of the work. The study of the weather elements on such a series of maps gives a far clearer understanding of the distribution of these elements and of their relation one with another, than if a far larger number of single maps are studied which do not follow one another in regular sequence. Teachers should add to the map-drawing exercises by giving their classes the data from other sets of maps selected from the school files. Summer maps as well as winter ones should be used, in order that too much emphasis may not be laid on winter conditions. The search for the various cities in which Weather Bureau stations are established, involved in the work of entering the data on the blank maps, furnishes excellent practice in geography. This exercise may be varied, and practice in the location of the different States may be given, if the teacher reads out to the class the temperatures in different parts of the various States, as, _e.g._, central Arizona, 34°; southwestern Tennessee, 30°; northern Nevada, 38°, etc. As the State names are not given on the Weather Bureau maps, such a method as this will give a very desirable familiarity with the relative positions of the States of the Union. If the school possesses a blackboard outline map of the United States, it may be a good plan, if the class is small, to have one of the pupils enter the temperatures and draw the isotherms on the board before the class, and to let the others correct him if they see that he is going wrong. As to irregularities in the isotherms, which may cause trouble, the officials of the Weather Bureau vary somewhat among themselves in dealing with such cases, and no definite rules can be laid down to fit all occasions. It is best to select maps with few irregularities at first, and in time experience will show how the exceptional cases may be treated. By the scheme of coloring isothermal maps, suggested in this chapter, a valuable series of permanent illustrations of noteworthy weather types for class use can readily be prepared at very slight cost. For the purposes of these colored illustrations it is best to use the large scale Washington blank weather maps, as suggested in the preceding chapter, and to have each map mounted on heavy cardboard after it has been colored. By means of this mounting the maps are prevented from tearing, and can be kept smooth and in good condition.