No. 89. Port Orchard, Wash., May 3, 1905.

Having been a subscriber for and purchaser of of every copy of Amateur Work which has been issued, I presume to seek the following advice: Between my office and home the distance is four miles, unobstructed salt water. Is it possible for me, an amateur, to operate a wireless telegraph between the two points with any degree of success? If so, what would be the probable cost of the necessary equipment, and would it be better to attempt to make, or buy the apparatus? If to buy, where can I purchase the most successful instruments, within the reach of the pocket-book of one who does not desire to spend any more money than is absolutely necessary to have a satisfactory working system, and not one that is more trouble than it is worth - if any such exist - which I wish, you would tell me honestly. J. G. B.

Replying to your letter of May 3. The location of your home and office, as you describe it, offers an exceptional opportunity for wireless communication. Success in wireless telegraphy depends as much on the amateur's understanding of the principles as upon the selection of instruments, for the best of apparatus on the market has its shortcomings, which can only be remedied by careful harmonizing of working conditions.

You will need a pole at each end, either a few feet high from the house top, or rising 40 to 50 feet from the ground. Each station will require a spark coil giving about 4-in. spark, and operated by 10 or more cells of dry battery. A smaller spark might suffice, but it is advisable to have reserve power over the requisite amount. Coils, in fact the entire sending end, may be constructed at home, if the maker has the time and materials.

It is difficult to express an opinion by letter as to the advisability of constructing all the " receiving" instruments at home. Amateurs have accomplished this at very moderate expense, but there are rules which can not be laid down specifically, each man's experience differing from that of every one else.

A coherer is difficult to make. A good one can be bought for $4. You can construct a sensitive relay for about $5 and a sounder for $1, or you can buy the coherer, decoherer, relay and sounder in the form of a set, of apparatus concerns, for from $25 to $35, according to accuracy and finish.

If we were in your place, we would commence a set of experiments, constructing the spark coil, pole wiring and other appurtenances of one sending end, as carefully as possible. Then purchase a coherer, and a 25-ohm relay of the regular telegraph type, and make experiments in the arrangement of apparatus until every depression of the sending key operates the receiving end. Having accomplished this construct a decoherer, descriptions of which have appeared in Amateur Work, and connect it in the relay circuit. Then experiment until the receiver receives each impulse and decoheres as it should. You may now purchase the sounder and complete the first receiving set. By experimenting as you build, you will be likely to save considerable money on the second set, which will be a duplicate of the first.

We have gone into all these details, not to discourage, but rather to interest you in what will prove most entertaining and instructive work. Even if you bought the most elaborate sets on the market at a cost of hundreds of dollars, there would be times when you would have to exercise all your ingenuity to make everything work. We have subscribers who have done as we advise you, and their results have been highly satisfactory, over much longer distances than required by you.

No. 90. Rochester, N. Y., May 9, 1905.

Will you kindly answer the following questions through your valuable magazine ? (1). How can a watch be demagnetized ? (2). What rated spark would be necessary for wireless telegraph stations at a distance of three miles? What would be the cost of the material providing I have purchased the coil?

L.W. O

(1). To properly demagnetize a watch, especially one of any value, is a rather .delicate operation requiring considerable experience and a suitable outfit, and we would not recommend any one unacquainted with the work attempting to do it. .

(2). A wireless telegraph outfit to operate over a distance of three miles on land would undoubtedly require a coil giving a 4 in. spark, but much depends upon the construction of the receiving end and local conditions. The cost would all depend upon how much of the apparatus was made by the owners, the coherers should be purchased, although it is recommended that some of the types described in the maga zine be made for the purpose of becoming familiar with their operation.

No. 91. Toledo, Ohio, May 26,1605.

Will a rheostat of the type described in Amateur Work, January, 1903, work well on alighting circuit of 110 volts, 19 amperes? I have not had success with it, as it did not cut the current down to the desired extent; in fact, not to any noticeable extent. Is carbon resistance suitable for controlling the motor or continuous work of any kind? Will it last as well as German silver wire? G. H. D.

The rheostat mentioned is not suitable, either in size or type, for the work mentioned. It is of much too small a capacity for the current, and it is fortunate that no harmful effects resulted from its use. It would have little appreciable effect in regulating a current of the volume named. We hope to publish, at an early date, a description of a rheostat suitable for regular lighting circuits. If only a small current is needed a lamp could be used to take most of the current, the balance being used as required.

No. 92. East Aurora, N. Y., May 9, 1905.

Can you tell me how to make a Tesla oscillator; also a small telescope? E. L. F.

A description of a Tesla oscillator of a size suitable to work with a Rhumkorff coil giving a 4-in. spark, is in preparation. The first chapter of a description of a reflector telescope appears in this issue. This instru-ment, while not large or difficult for the amateur of fair skill, is of a size which will permit of very interesting and valuable astronomical work.

No. 93. New Haven, Conn., May 4, 1905.

1 have a lathe built on the plan given in the Amateur Work for July, August and September, 1903. The way I have of driving it at present is not satisfactory, so I would like particulars of a motor strong enough to drive it. Where can I get a motor or the castings for one ? What fraction of a horse power is necessary? What voltage would be required? What type of battery would be best? H. S. P.

The power required to drive a turning lathe, even of such a small size as the one you have, is greater than might be thought until actual experience has shown this to be so. A quarter horse power motor would be necessary to give the power and speed on heavy work, and sufficient power should always be provided to take care of the heaviest work a machine is given. For light work or light cuts on heavy work, less power might answer, say one-eighth horse power, but to run an electric motor of even the smaller power by battery current, would call for an expensive battery outfit as well as heavy expense of maintenance. A storage bat-tery would not be expensive to maintain, if one had the charging facilities.

The most suitable driving device for the lathe is a drive wheel operated by treadle. A stand can be made of wood, the drive wheel keyed to a shaft, on each end of which are lugs and bolts to connect with treadle rods to the treadle. This gives ample power, is inexpensive to fit up and costs nothing to run.

No. 95. Jacrsonville, III., May 14, 1905.

Will you kindly answer the following questions relative to wireless telegraph apparatus described in the November and December, 1904, numbers:

1. What should be the resistance of the variable inductance coil described in the November number?

2. What capacity should the Leyden jars be for the battery described in the same number and how many jars should be used?

3. Using a coil giving a one-inch spark, how far is it possible to transmit and receive signals, with the apparatus described in the November and December numbers? C. B. V.

The resistance of the variable inductance should be as low as possible, using as heavy as No. 12 gauge copper wire, or even larger. The capacity of the Leyden jars should be .0005 M. F. each for coils up to 2 in. spark. With a 50-ft. aerial wire at each end and very sensitive coherers, relays, etc., it is possible to send, with a coil giving a 1-in. spark, for a distance of one mile over land, or even further, but local conditions have considerable bearing on the results attained, no fixed rule being possible.