No. 103. Santa Barara, Cal., Aug. 8, 1905.

I would like to ask a few questions relative to using an alternating current to excite an induction coil giving a two-inch spark or larger capacity.

Can good results be obtained by using an alternating current of 7200 frequency and 110 volts?

Can a condenser be used in this arrangement? If so, how is it connected ? W. C. TAlternating currents are frequently used for coil work, where the coil is large enough to permit of it. If the current is obtained from a commercial circuit, a lamp or other resistance will be necessary, unless the coil is a very large one. Specific directions cannot be given without knowing the primary winding. Consult the manager of the central lighting station on this point.

The frequency you mention is so very high that you have undoubtedly confused it with the frequency per hour. In all probability it is the usual circuit of 60 cycles (120 frequency.)

The condenser should be used and connected across the secondary.

No. 104. Kansas City, Mo., Aug. 18, 1905.

I am very much interested in Amateur Work and eagerly read each copy as soon as received.

I would like to have you publish an article on how to build a boiler capable of furnishing steam for 1/2 to 1 h. p. engine or steam turbine, Also one on the building of a steam turbine of about these powers, and a four pole dynamo with semi-enclosed fields to run direct connected with same.

Referring to the boiler, I think directions for burning crude oil as fuel would be of interest to those living in the sections of the country where such oil is cheap. L. E. P.

We gladly welcome letters containing suggestions like the above. Those mentioned have been receiving our attention for some time, and articles are already under way for most of them. The steam turbine will undoubtedly fill a very important place in the motive world in the near future, and amateurs will naturally be interested to study the principles of their construction and operation through model making. We would also add that motive powers of various kinds will be given a prominent place during the forthcoming year.

No. 105. Davisville, N. H., Aug. 11, 1905.

I have a wireless telegraph pole which is set upon the roof of my house. The pole is about 28 feet high. I have a telegraph wire on each side of it. Would this pole be all right for sending and receiving messages for a distance of about two miles? W. L. K.

It has been frequently stated in this department that the distance over which wireless telegraph messages may be transmitted cannot be determined from any one part of the apparatus, but is dependent upon the design and construction of all parts, and also the character and elevation of the country in which it is used. An efficient sending station would lose much of its value if the receiving station was not equally as efficient.

In the location and height of the pole the object is to obtain a clear and open interval between stations, as high above the intervening country as convenient, so that influences likely to disturb the transmission of the wave impulses may be avoided,

No. 106. Lompoc, Cal., July 19, 1905.

I would like to see an article describing how to make a simple water motor of about 1/8 to 1/4 h. p., the turning work on same to be done on a lathe like the " Amateur. " T. D. L.

Our experience with water motors leads us to believe that to make one which would work satisfactorily requires a metal-working lathe, that same may be perfectly balanced. An unbalanced water-motor is about the noisiest and most troublesome device which can be used for power. To develop 1/4 h. p. at 90 pounds pressure would require an 8 or 9 in. wheel, or larger than the capacity of the 'Amateur." lathe. We expect to soon be able to offer an efficient water motor as a premium upon such favorable terms as to make it much easier to obtain it in that way than to try and make one.

The driving and holding powers of nails have been investigated by Prof. Carpenter of Cornell, whose experiments seem to show that much more force is required to drive a cut nail a given distance than a wire nail; that more force is required to start a cut nail than to drive it, and that it invariably starts much harder than a wire nail; that the work required to drive cut nails is much more than to drive wire nails; and that the work in withdrawing cut nails is about equal to that in withdrawing wire nails, it being sometimes less and sometimes greater. The relative efficiency which is here considered as the ratio of the work of pulling to that of driving is much higher for the wire nail than for the cut nail. The cut nail bruised and broke the fibres of the wood, principally at the end of the nail, whereas the wire nail simply crowded them apart, and probably did not move them much beyond the point from which they would return by elastic force, and hence the nail would be grasped much stronger per unit of area of surface by the wood. Presenting less surface, there would be, however, less resistance to starting. To see what the effect of change of form would be, a number of tenpenny cut nails were sharpened on the point by grinding to an angle of about 30°, so that the fibres in advance of the nail would be thrust aside and not bruised and broken. This increased the holding power of the nail, decreased the force necessary to start it, and increased the resistance to withdrawal.