Page:United States patent 586193.pdf/5
balls of solid brass of four inches diameter, giving oscillations of ten inches length of wave.
The reflectors applied to the receiver and the 105transmitter ought to be preferably in length and opening the double at least of the length of wave emitted from the oscillator.
If a very powerful source of electricity giving a very long spark be employed, it is 110preferable to divide the spark gap between the central balls of the oscillator into several smaller gaps in series. This may be done by introducing between the big balls smaller ones, (of about half an inch diameter,) held 115in position by ebonite frames.
I find that the regularity and power of the discharge of an ordinary Ruhmkorff coil with a trembler-break on its primary, is greatly improved by causing one of the contacts of the 120vibrating break to revolve rapidly. I do this by having a revoluble central core c2, Fig. 3, in the ordinary screw c3, which is in communication with the platinum contacts. I cause the said central core with one of the 125platinum contacts attached to it to revolve by connecting it to a small electric motor c4. This motor can be worked by the same circuit that works the coil, or, if necessary, by a separate circuit. The connections are not 130shown in the drawings. By this means the platinums are kept smooth and any tendency to stick is removed. They last also much longer. At the receiving-station is a battery whose circuit includes an ordinary telegraphic 135instrument (or it may be a relay or other apparatus which it is desired to work from a distance) and a circuit-closer.
In Fig. 4, g is the battery, and h a telegraphic instrument on the derived circuit of 140a relay n.
The appliance I employ as a circuit-closer is shown full size at Fig. 5 and consists of a glass tube j, containing metallic powder or grains of metal j{1 each end of the column of 145powder being connected to a metallic plate k of Suitable length to cause the system to resonate electrically in unison with the electrical oscillations transmitted. The glass tube may be replaced in some cases by one of 150gutta-percha or like material. Two short pieces of thick silver wire j2 of the same diameter as the internal diameter of the tube j, so as to fit tightly in it, are joined to two pieces of platinum wire j3. The tube is closed and 155sealed onto the platinum wires j3 at both ends.
Many metals can be employed for producing the powder or filings j1, but I prefer to use a mixture of two or more different metals. I find hard nickel to be the best metal, and 160I prefer to add to the nickel filings about ten percent. of hard-silver filings, which increase greatly the sensitiveness of the tube to electric oscillations. By increasing the proportion of silver powder or grains the sensitiveness165 of the tube also increases; but it is better for ordinary work not to have a tube of too great sensitiveness, as it might be influenced by atmospheric or other electricity. The sensitiveness can also be increased by adding a very small amount of mercury to170 the filings and mixing up until the mercury is absorbed.
The mercury must not be in such a quantity as to clot or cake the filings. An almost imperceptible globule is sufficient for a tube.175 Instead of mixing the mercury with the powder one can obtain the same effects by slightly amalgamating the inner surfaces of the plugs which are to be in contact with the filings. Very little mercury must be used, just 180sufficient to brighten the surface of the metallic plugs without showing any free globules. The size of the tube and the distance between the two metallic stops may vary under certain limits. The greater the space allowed for the185 powder the larger and coarser ought to be the filings or grains.
I prefer to make my sensitive tubes of the following size: The tube j is one and one-half inches long and one-tenth or one-twelfth of an190 inch internal diameter. The length of the stops j2 is about one-fifth of an inch, and the distance between the stops is about one-thirtieth of an inch. I find that the smaller the space between the stops in the tube the more195 sensitive it proves, but the space cannot under ordinary circumstances be excessively shortened without injuring the fidelity of the transmission.
The metallic powders ought not to be fine,200 but rather as coarse as can be produced by a large and rough file.
All the very fine powder ought to be removed by blowing or sifting.
The powder ought not to be compressed 205between the stops, but rather loose and in such a condition that when the tube is tapped the powder may be seen to move.
The tube must be sealed, but a vacuum inside it is not essential, except the slight 210vacuum which results from having heated it while sealing it. Care must also be taken not to heat the tube too much in the center when sealing it, as it would oxidize the surfaces of the silver stops and also the powder, which would215 diminish its sensitiveness. I use in sealing the tubes a hydrogen and air flame. A vacuum is, however, desirable, and I have used one of about one one-thousandth of an atmosphere, obtained by a mercury-pump. It is also220 necessary for the powder or grains to be dry and free from grease or dirt, and the files used in producing the same ought to be frequently washed and dried and used when warm.
If the tube has been well made, it should be225 sensitive to the induction of an ordinary electric bell when the same is working at one to two yards or more from the tube.
In order to keep the sensitive tube j in good working order, it is desirable, but not 230absolutely necessary, not to allow more than one milliampere to flow through it, when active. If a stronger current is necessary, several tubes may be put in derivation between the