Our readers are invited to contribute to this department, but no responsibility is assumed for the opinions expressed in these communications.

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Illustrate the subject when possible by a drawing or photograph with dimensions.

Readers who desire to purchase articles not advertised in our columns will be furnished the addresses of dealers or manufacturers, if stamp is enclosed with request.

(No. 17.)

Buffalo, N. Y., June 29, 1902.

Can you tell me who manufactures steam engines and boilers of 1/4, 1/2 and 1 H. P. A. M.

B. R. Wicks, Bridgeport, Conn., and Sipp Electric and Machine Company, Paterson, N. J., make such engines, and the latter firm make boilers. They will send circulars and prices upon application.

(No. 18.)

Albany, N. Y., July 11, 1902.

In the article descriptive of an " Electric Wind Vane," a steel rod is used as an axis for the vane. As this part of the instrument is put on top of the house, would it not be dangerous in case of thunderstorms ? If so, can you tell me a way to avoid the trouble?

W. S

Little fear need be felt that lightning will be attracted by such a small rod as is required for the weather vane. A lightning arrester can be added if desired, a description of one being given in this issue of the magazine.

(No. 19.)

Cambridge, Mass., July 11, 1902.

Will you please tell me where and at what price a wire gauge can be purchased? V. J. B.

A wire gauge, English standard, 5 to 36, list price, $1.00; American standard, 5 to 36, $2.00. You should be able to get such gauges at any large hardware store. If desired for electrical wire, you should get the American gauge.

(No. 20.)

Antigo, Wis., July 7, 1902.

Please inform me the weight of wire required for the primary and secondary coils of the medical coil described in the February issue. K. G. M.

About one-half pound of each size will be required for the coil.

(No. 21.)

Boston, Mass., July 22, 1902. I have completed the spark coil which was described in the June number, but cannot make it work satisfactorily. The amount of current passing through the secondary coil was very light. It was even so small that one would have to place the wires on his tongue to be able to detect the current. Please advise what I may do to improve it. E. A. W.

First test the primary coil, and if this is found to be all right, there is undoubtedly a break somewhere in the secondary coil. It may be in the leading-out wires, as these are quite likely to get broken when mounting the coil. If a careful examination does not locate the fault here, the best thing to do is to rewind the secondary, making careful tests of the wire before doing so. Several readers of the magazine have made these coils from the directions given, and are getting good fat sparks over an inch long, one reporting a 6park over 11/2" long.

Notice

Robert Thistle white, Dover, Morris County, N. J., writes that the sets of motor castings offered free to readers of this magazine, who should write for them, were so quickly applied for that the supply became exhausted. Another supply will soon be ready, and all requests on file will be filled.