Part 110

The spiral spring on the latch bolt is lighter than the one above it. This gives an easy, lively action to the bolt, with very little friction when the door is closed, while the heavier spring above gives a quick and positive action of the knobs.

What Happens When the Key is Turned?

All of that portion of the lock which is shown below the round central post is operated by the key. The square stud is attached to the bolt, and in figure 1, it is seen that the projections on the flat tumblers prevent the stud from moving forward, holding the bolt in retracted position. When the key is turned as shown in figure 2, it raises the tumblers releasing the stud, and then pushes the bolt out, the tumblers falling into position as shown in figure 3, with the projections again engaging the stud and preventing the bolt from moving until the key is turned backward, again raising the tumblers and releasing and retracting the bolt.

How Key Changes Are Provided.

There are three ways in which keys are made individual to the locks they fit.

a. By changing the shape of the keyhole. This may be done shorter or longer, wide or narrow, straight or tapering and with projections on the sides which the key must fit, making it difficult or impossible for keys of a different class to enter the lock. In the lock shown, a projection on the keyhole will be noted, fitting a groove in the bit of the key.

b. By wards attached to the lock-case. The two crescent-shaped wards seen near the key in figure 2 illustrate this feature. Similar wards are placed on the lock cover. These fit into the two notches shown on the key bit in figure 4, and their shape and position are varied at will.

c. By changes in the tumblers. There are five flat tumblers in the lock shown, and their lower edges fit into the end of the key bit. By varying their height, changes in the cutting of the key are made necessary.

The security of a lock depends very largely upon its being so made that no key will operate it except the one which belongs to it, and this is obtained by guarding the keyhole by means of a, by preventing the wrong key from turning by means of b, and by still further limitations by means of c.

FACE OF CYLINDER LOCK.]

The Cylinder Lock.

Door locks of the highest grade of security are made with a locking cylinder, which contains tumblers in the form of miniature bolts which make it impossible to operate the lock except with the key to which it is fitted. This is screwed into the lock-case through the side of the door, with the lever on the inner end engaging the end of the bolt in the lock, so that as it is moved it either retracts or “throws” the bolt as desired.

Figure 1 shows all the parts of a modern master-keyed lock. Figure 4 shows a broken view of the cylinder with all parts in position. Figure 3 shows a simpler form used when the master key is not desired. Figure 2 shows the front, the only part which is visible when the lock is in use, with its keyway of tortuous shape which will not admit flat-picking tools.

When the lock is assembled, the pin tumblers project through the shell, the master cylinder and the key plug holding all parts firmly bolted or fastened together. When the proper key is inserted, the tumblers are raised until the “breaks” in all of them coincide with the surface of the key plug, releasing it and permitting the key to turn it. If any one of the five tumblers is .002 inch too high or too low, the key will not turn; so that no key except the one made for the lock can be used.

In the master-keyed lock, the master key causes the breaks to coincide with the outer surface of the master ring. It is thus possible to have a master key which will fit any desired number of locks with the individual or change keys all different from each other and from the master key.

The balls reduce friction to such an extent that a key has been inserted and withdrawn for a million times without affecting the accuracy of the lock.

INTERIOR OF CYLINDER LOCK WITHOUT MASTER KEY.]

INTERIOR OF MASTER-KEYED CYLINDER LOCK.]

Where Does Salt Come From?

Salt is one of the things with which we come in contact with daily perhaps more than any other. With the exception of water, probably no one thing is used more by all civilized people than salt.

You have already learned in our talk on elements the difference between a mere mixture of substances and a chemical compound. You remember that when some substances are only mixed together, they do not lose their identity. In a compound the substances are always combined in fixed proportions and the properties of the compound are often very different from those of the things that make it. Common salt is made of two substances, that are not at all like salt, and are very different from each other. One, sodium, is a soft, bluish metal, and the other is chlorine, a yellowish-green gas. The chemical name for salt is sodium chloride which is derived from the two names sodium and chlorine.

Sodium and chlorine are both what we have learned to call elements. An element being a substance which cannot be separated into substances of different kinds. There are now known about seventy such elements. All the substances around us are composed of these elements alone, or chemically united in different compounds, or simply mixed together. Most of them, however, are mixtures, not of separate elements, but of compounds. The soil under our feet is a mixture of compounds. Water is also a compound. Pure compounds very rarely occur naturally. Salt is sometimes found almost pure; but generally is mixed with so many other things that we have to take them out to get absolutely pure salt. For practical every-day use it is unnecessary to purify the salt.

Salt is found in large quantities in the sea water, in which it is dissolved with some other substances. It is also found in salt beds, formed by the drying up of old lakes that have no outlets; salt wells, that yield strong brine; and salt mines, in which it is found in hard, solid, transparent crystals, called rock salt. Rock salt is the purest form in which salt is found and, to prepare it for market, it is merely necessary to grind it or cut into blocks. The greatest deposit of salt in the world is probably that at Wielizka in Poland, where there is a bed 500 miles long, 20 miles wide, and 1,200 feet thick. Some of the mines there are so extensive that it is said some of the miners spend all their lives in them, never coming to the surface of the earth.

A trip through these mines is interesting. In one of them can be seen a church made entirely of salt. The salt supply of the United States is obtained chiefly from the salt wells of Michigan and New York, the Great Salt Lake in Utah, and the rock-salt mines of Louisiana and Kansas.

In the arts and manufactures, the most important uses of salt are in glazing earthenware, in extracting metals from their ores, in preserving meats and hides, in fertilizing arid soil, and also, as we shall presently see, in the manufacture of soda. Of equal importance, perhaps, is its use in food. Most people think it not only lends a pleasant flavor, but is itself an important article of diet. It is certain, that all people who can obtain it use salt in their food, and where it is scarce, it is considered one of the greatest of luxuries.

Soda is of interest to us, not so much on account of its use in our households, as because it plays on extremely important part in two industries that contribute greatly to our comfort, viz., the manufacture of glass and soap.

Soda is not found naturally in great abundance, as salt is, but is generally made from other substances. Formerly it was made almost entirely from the ashes of certain plants. One, known as the Salsoda soda-plant, was formerly cultivated in Spain for the soda contained in it, and the ashes, or Barilla, as they were called, were soaked in water to dissolve out the soda. Now, however, the world’s soda supply is produced from common salt by two processes, known from the names of their inventors as the Leblanc and Solvay processes.

~WHERE WE GET SODA~