SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING As to using comparison and contrast in extended form, we find that there are, broadly speaking, four ways of presenting material By the first method, we may fully present one item and then fully present the other, making continuous reference to the points of comparison or contrast. This method is, in general, appropriate when the points to set against each other are fairly broad, and obvious. By the second method, we present a part of one item and then a part of the second in relation to the corresponding part of the first item, until we have touched on all relevant parts. When a great many details are invol ved, this method is likely to be more useful than the first. By the third method we present one item fully and then, in presenting the second, refer, part by part, to the first item. Finally, the fourth method generally involves a mixture of the three types we have just described Now let us observe the following two excerptsSCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING As to using comparison and contrast in extended form, we find that there are, broadly speaking, four ways of presenting material. By the first method, we may fully present one item and then fully present the other, making continuous reference to the points of comparison or contrast. This method is, in general, appropriate when the points to set against each other are fairly broad, and obvious. By the second method, we present a part of one item and then a part of the second in relation to the corresponding part of the first item, until we have touched on all relevant parts. When a great many details are involved, this method is likely to be more useful than the first. By the third method, we present one item fully, and then, in presenting the second, refer, part by part, to the first item. Finally, the fourth method generally involves a mixture of the three types we have just described. Now let us observe the following two excerpts