For manufacturing processes, one importance of steam-power rests in the fact that such power can be taken to the material; and beside other advantages gained thereby, is the difference in the expense of transporting manufactured products and the raw material. In the case of iron manufacture, for example, it would cost ten times as much to transport the ore and the fuel used in smelting as it does to transport the manufactured iron; steam-power saves this difference, and without such power our present iron traffic would be impossible. In a great many manufacturing processes steam is required for heating, bleaching, boiling, and so on; besides, steam is now to a large extent employed for warming buildings, so that even when water or other power is employed, in most cases steam-generating apparatus has to be set up in addition. In many cases waste [31] steam or waste heat from a steam-engine can be employed for the purposes named, saving most of the expense that must be incurred if special apparatus is employed.Every one who uses tools should understand how to temper them, whether they be for iron or wood. Experiments with tempered tools is the only means of determining the proper degree of hardness, and as smiths, except with their own tools, have to rely upon the explanations of others as to proper hardening, it follows that tempering is generally a source of complaint.
FORE:Yet she was restless and uneasy. She had never known what it was to be nervous before. There was a dull booming noise somewhere, a knocking that seemed to proceed from the Corner House. Hetty heard something fall with a thud, she could have sworn to a stifled cry. A door opened and closed somewhere, there was a strong draught as if the basement had been opened. Hetty's heart was beating in some strange, unaccountable way. A little cry brought her to her feet.
An interesting study in connection with modern shaping machines is the principle of various devices called 'quick return' movements. Such devices consist of various modifications of slotted levers, and what is known as Whitworth's quick return motion.VI.126