No. 154. Paris, Tex., June 7, 1906.

Will you please answer the following questions:

1. Does beat destroy the resistance of German silver wire?

2. In using wire like samples enclosed (Nos. 23 and 30 gauge) for a 1/2 in. spark coil, what would be the specifications for winding, using the larger wire for the primary?

S. Please give directions for making a transmitter to work on a line 300 ft. long.

4. Could German silver filings be used in a coherer together with nickel filings. P. C.

Heat increases the resistance of all metals excepting carbon, but the rate of increase varies with different metals. It is very small for German silver, which is only one ninth that of copper.

2. The samples of wire you enclose are not suitable for making up spark coils. The larger gauge is too small for the primary, and the finer one too large for the secondary. As the cost of suitable wire for a coil to give a 1/2-in. spark is small, it ;would be advisable to purchase new wire.

3. An answer to this question requires too much space for this department. A special article will be published as soon as it can be prepared.

4. A coherer should be made as efficient as possible, as they are not any too sensitive at best. We have yet to learn of German silver filings having any advantages over the usual iron and nickel combination.

No. 155. Summit, N. Y., June 18, 06.

Will you kindly answer the following questions:

I desire to connect my workshop in the barn with the house by telephone, but do not care to spend a large sum to do so. Will you tell me the cheapest and simplest method for doing it? The distance is about 300 feet, and I have two single pole receivers. Can they be wired up to serve the purpose? Would it pay to use magneto generators for calling instead of batteries? Please send me a diagram of the connections of small, two station telephones. Is it possible to connect another instrument to these telephones by using extra wires, or other mechanism, etc. If so, please send diagram. A. J. M.

Two ordinary telephone receivers can be used for a telephone line by having a complete metallic circuit of insulated wire, except in the open air, where bare wire may be used. The connections should be made so that the coil windings of each transmitter will send the current in the same direction around the line; or, in other words, one coil should not oppose the other. The distance you mention is rather too loug for satisfactory results by this method, and a microphone transmitter will probably be necessary. An article describing a simple and inexpensive telephone, suitable for distances up to 200 yards, will be published in an early issue. Magneto generators are necessary for calling only when the distance is greater than that for which a battery current is adapted, about 500 yards. The desired diagrams are enclosed with answer. Several battery telephones can be connected together by using an extra wire for each added station over two, and two extra wires for the ringing circuit.

No. 156. Somervwlle, Mass., July 4, 1906.

What size spark could I expect to get with a 10-volt current from a coil made as follows: - Coil is 10 in. long and 6 1/2 in. diameter, with secondary made in eight sections, of No. 28 gauge wire. There are three layers of paper between each layer of wire. Shellac is used as an insulator. What size spark would I get on a circuit, cut down by a resistance of sulphuric acid batteries. J. P. C.

The information given is not adequate to even hazard a guess as to the length of spark possible from the coil, but the size of wire used in the sesondary and the excess of paper between layers would indicate a very small spark. Complete specifications as to core, primary, secondary and insulation are necessary to calculate the capacity of a coil, and even then the workmanship is a large factor in determining the output. If the primary will carry a 112-volt current, presumedly from a lighting main, the spark might be increased slightly, but the information given indicates that the proportions of the coil are faulty.

No. 157 Minneapolis Minn., June 10, 1906.

Will you please tell me whether or not an alternator will take the place of a current breaker and condenser. J. A. Fleming, in "Magnets and Electric Currents" says: "The condenser is, therefore, an essential adjunct in a coil intended to give long sparks from the secondary circuit, but is of no value if the induction coil is used with alternating currents. " Can you tell me whether it is advisable to use an alternator? In the above I refer to the use of a 12-in. coil for use in wireless telegraphy. W. C. R.

An alternating current dynamo may be used to furnish current for operating induction coils in place of a direct current. In such a case, the vibrator, if there is one, is screwed up tight against the core and the condenser cut out of circuit. Currents from alternating lighting circuits are frequently used for coils, but special interrupting apparatus is generally needed to enable such currents to be used satisfactorily, especially with large coils. It is desirable that the alternating dynamo, where one is used especially for coil work, be specially designed for the purpose. We have no knowledge of anything in print giving information on just the points you mention, and we therefore will have an article prepared in which this information will be fully treated.