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Previous to taking off the verge, oil all the pivots in front; let the clock be wound up about half way, then take off the verge, and let it run down as rapidly as it will, in order to work out the gummy oil: then wipe off the black oil that has worked out and it is not necessary to add any more to the pivots.
The rising and falling front gives a power of modifying the field of view in a vertical direction. The swing back preserves the verticality of architectural subjects. In some cases, when used with the pivots vertical, it is a help in focussing the subject.
The conical form is given to the drill for exactly the same reason that it is given to the balance pivots, because it gives additional strength. We are now ready to temper our drill, and we must exercise a little care that the steel is not burnt and that the drill is not bent or warped when hardening.
"They are a pair of rings," replied the surgeon, "one within the other, and each mounted on pivots in such a manner that any thing hung within the inner ring will swing any way freely. The lamps down in the cabin are hung on gimbals." "Yes," said Rollo, "I saw them."
The nations, therefore, that lie midway between the pivots at the southern and the northern extremities of the axis, converse in a voice of middle pitch, like the notes in the middle of a musical scale; but, as we proceed towards the north, the distances to the heaven become greater, and so the nations there, whose vocal utterance is reduced by the moisture to the "hypatès" and to "proslambanomenon," are naturally obliged to speak in heavier tones.
Self-respect and respect for others, the sensitive consciousness poises itself in these as the compass in the ship's binnacle balances itself and maintains its true level within the two concentric rings that suspend it on their pivots. This thoroughbred school-girl quite enchanted Mr. Bernard. He could not understand where she got her style, her way of dress, her enunciation, her easy manners.
I draw the temper in the following manner: Place some fine brass filings in a boiling-out cup or bluing pan and lay the blank upon these filings, holding the pan over the flame of an alcohol lamp until the blank assumes a dark purple color, which it will reach when the heat gets to about 500° F. This I consider the right hardness for a balance staff, as it is not too hard to work well under the graver nor too soft for the pivots.
The conical pivot has at least one advantage over the straight one, i. e., it can be made much smaller than a straight pivot, as it is much stronger in proportion, owing to its shape. All pivots have a tendency to draw the oil away from the jewels, and particularly the conically formed variety, which develops a strong capillary attraction.
Upon one face a semicircular hollow or socket may be noticed, in which the foot of the bronze pivots, or rather the pivot shod and faced with bronze, upon which the heavy timber doors and their casings of metal were hung, had to turn. The marks of the consequent friction are still clearly visible.
The width of this piece should be four inches, and the length eight inches. Before nailing the boards together, the holes thus left in the bottom board should be supplied with a treadle platform, working on central side pivots.
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