SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING The informal instinctive use of comparison and contrast is useful, but we can make the method infinitely more useful in thinking and expressing ourselves, if we are systematic To be systematic means to understand the kinds of purpose for which the first method may be made We may distinguish three types of purpose. First, we may wish to present information about one item and may do so by relating it to another item with which our readers are familiar. For example, if we wish to explain the heat treatment, we may do so by comparing it with cooking which changes the structure of foodSCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING The informal instinctive use of comparison and contrast is useful, but we can make the method infinitely more useful in thinking and expressing ourselves, if we are systematic. To be systematic means to understand the kinds of purpose for which the first method may be made. We may distinguish three types of purpose. First, we may wish to present information about one item and may do so by relating it to another item with which our readers are familiar. For example, if we wish to explain the heat treatment, we may do so by comparing it with cooking, which changes the structure of food