Paul M. Benedict.

If one takes any interest in meteorology it fre-quently happens that it would be very convenient to be able to know the direction from which the wind is blowing without going out-of-doors to look at a wind-vane. At night, and especially if the wind is light, it is rather difficult to ascertain the direction of the wind. I constructed, some time ago, for my own use, an instrument which will show at any time the "wind direction," and for want of a better name I have called it an electric wind-vane. The vane will not tell the wind direction to a degree, but it will tell it to eight points of the compass, and by the expenditure of a little more time and money, can be made to show sixteen points, but eight is, as a rule, quite close enough. The instruments used in most of the meteorological stations only show eight points.

The material needed is as follows : Enough planed board 7/8" thick (white wood or pine will do) to make a box 6" x 6" x 8", inside measurements, a thin board 1/4" thick and 31/2" x 12", or, failing this, a piece of heavy sheet iron or tin of the same size, also a piece of heavy sheet brass 5/42" square and about 1/16" thick, a Stubbs steel rod 1/4" diameter and 14" long, which must be quite straight, eight round-head brass screws 3/4" long and about 1/8" diameter, about two dozen screws for making the wooden box mentioned above, a small strip of thin spring brass 2" long and 1/4" wide, and an ordinary paraffin candle. This completes the materials for the wind-vane part of the apparatus.

For the "indicator," which is in the house and is in electrical connection with the wind-vane, the brator. The post of the vibrator is connected to the other battery binding-post. The condenser should be put inside the base and one end connected to the post of the vibrator and the other end to the vibrator spring. All connecting wires should be earned inside the base, small holes being bored in the top where needed.

following materials are needed: Measure the approximate distance from where you will set the vane on the roof of the house to where you will put the indicator, and get enough insulated copper bell wire, No. 16, to reach five times the distance; 250' will usually be ample. Also about \ lb. of double covered copper magnet wire, No. 18 ; five small binding-posts; a small magnetic compass (see that the needle swings freely) ; four round-head iron rivets 1/4" diameter and 1" long ; also the metal case of an old alarm clock, six small round-head brass screws about 1/2" long, some rubber tape (piping), a small one-point switch, and two cells of any good open-circuit battery.

Take the 51/2" square piece of sheet brass and strike a circle on it 51/2" in diameter (Fig. 2). Mark out a diameter and another at right angles with it; drill holes at the places marked 1, 2, 3, etc. (Fig. 2), large enough for the eight round-head brass screws to pass through. Now saw the corners off with a hack-saw and file smooth until you have a nice circle 51/2" diameter. Next cut the circle into four parts; along the diameters previously marked, cut off the surplus metal inside of the 2" circle and finish smooth with a file. Saw out and plane up the pieces of wood for the box, which is to measure 6" x 6" x 8" inside.

After the pieces have been planed, they must be soaked in melted paraffin for ten minutes, or lay some lumps of the paraffin on the wood and pass a hot iron over it. This is done to prevent the box from warping. A varnished or painted box will be useless in a couple of months. Take the piece which is to form the top of the box, and drill a hole exactly in the center a little over 1/4" diameter, to allow the steel rod to slip through it easily (see Fig. 1). On the bottom piece of the box strike two circles, 2" and 51/2" in diameter. Drill a hole in the end of the steel rod about 1/8" deep and the same in diameter. Get a round-head brass screw 1" long and file the point so that it will slip into the hole in the end of the rod, making an easy fit and letting the rod turn freely. This forms one of the bearings of the steel rod (Fig. 1). Now take the square piece of brass and drill a 1/4" hole in its center, enlarging with a round file if necessary, so that the steel rod will turn easily in it. This forms the other bearing (Fig. 1). Screw to the top of the box, so that the hole in the brass will coincide with the hole in the wood. Then screw the four brass sections, N. E. S. W. (Fig. 2), on the bottom of the box, so as to fit the 51/2" and 2" circles previously marked, taking care that the pieces do not touch each other at any point. Leave the outside screws loose. Drill four small holes through bottom piece of box, near the outside screws in the brass pieces, to receive the connecting wire. Run a piece of the bell wire about 1 long up through each of these holes, turning a bare end under the head of each outside screw. Connect another piece of wire to the brass screw (Fig. 1) and see that it does not touch any of the brass sectors or screws in them.

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Now take the piece of thin spring brass and solder it at right angles to the steel rod (E, Fig. 1), about 1" from the end which has the small hole drilled in it. To do this, make the rod rough with a file and then rub a piece of brass over the rough piece. The rod will take a thin coating of brass, and by using strong chloride of zinc as a wash, or a soldering paste, it is easy to solder the brass to the steel. Bend the brass spring again at right angles about 1/2" from the free end with a slight upward curve at the outer end, so as to form a "brush" or " shoe " (U, Fig. 2), which, when the steel rod is in place, will slide around on the brass sectors, as the rod turns in either direction, without hitting the screws in the sectors and without catching in the slots between them. Slip the top piece of the box, with the square piece of brass screwed to it, on to the steel rod and proceed to put the box together, leaving out one side. If the box cannot be set on something flat on the roof of the house, a firm, level support should be made for it. Attach the vane (the piece of thin wood or sheet iron) to the steel rod by small cleats (B and B', Fig. 1), and the vane is completed.

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For the indicator obtain the metal case of an old alarm clock and make a baseboard 1/4" thick to fit the bottom of it. The side of the clock may be cut down with a hack-saw so that it will not be over \\" high. Screw it to the baseboard with small round-head brass screws. Make a second baseboard 51/2" square and mark a circle in the center of the diameter of the clock case.

Take the four rivets and anneal them, which may be done by putting them in the kitchen fire and leaving them to cool slowly as the fire goes out at night. When annealed, wind the shank with one thickness of rubber tape or four thicknesses of waxed paper, and then wind on four layers of the No. 18 cotton-covered magnet wire, beginning at the head, leaving 6" of free wire on each end for connections. Tie down the outside ends with twine. We now have four small electro-magnets. Mark a circle on the upper baseboard 2" in diameter. Mark out a diameter and one at right angles, and where they meet the circle bore four holes through both baseboards just large enough to receive the magnets, which should be pushed into the holes with the heads on the upper side. If necessary, wrap a little paper around them to make them fit tightly. The ends for connections should be on the underside. Put the five binding-posts on the outside baseboard, one in each corner and one in the center of one side, and run the outside end of the wire on each magnet to a post. Connect all inside ends together and run a wire from them to the fifth binding-post. Take the glass top off the little compass and then stick a sharp needle point up in the center of the baseboard, so that when the compass needle is placed on it, the top of the pivot will be about §" from the baseboard.

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The needle must stand straight and the compass needle swing freely on it. Get some good white cardboard and cut out a circle which will just fit inside the case. Mark two circles near the edge in ink, one about 1/2" inside the other, and then divide the circles into four equal parts and mark each line N. E. S. W. like a compass. Push the disc of cardboard down over the needle and turn it until the mark X. is opposite one of the magnets, then push it down so as to rest on them.

To connect the two parts, cut five pieces of the bell wire the necessary length, and mark four of the wires at each end with tags on each for N. E. S. W. Different colors of bell wire may be used if obtainable and the tagging avoided. Twist the five ends together and fasten to a nail or any convenient support, and at every two feet or so wind a few turns of rubber tape or twine around them. In this way a very good cable may be made. Set up the indicator in the house on a level support. Set up the vane-box on the roof of the house ; it should be above anything on the roof. If necessary, put it on a pole and secure it by guy wires. The box must be level and the rod perpendicular or the vane will not swing true in a light wind. Turn the box on its support so that two of the brass sectors are in the N. and S. lines, and the narrower spaces between them lie N.-E., S.-E., etc. Turn the steel rod so that the little brush is on the center of the sector on the north, and then turn the wooden or sheet-iron vane on the rod so that it will be just opposite the brush, and clamp it there, so that when the wind causes the vane to point north, the brush will point N. and make contact with the N. sector (Fig. 2).

Connect one end of wire marked N. to the sector N. and the other end to the binding-post which is in connection with the magnet opposite N. on the cardboard dial. Connect the other wires and sectors in the same way. Connect the fifth wire in the cable to the screw forming the lower bearing of the steel rod, and somewhere near the other end connect it to one pole of the battery of two dry cells. Lead a wire from the other pole of the battery to the switch and one from the point of switch to the fifth binding-post on the indicator which is in connection with all the inside wires of the electro-magnets. If everything is rightly made and connected, on closing the switch the compass needle will swing around and point on the dial to the direction from which the wind is blowing. If the needle keeps jumping from N. to E. or E. to N., the wind direction is N. E., etc. If the wrong end of the needle points to the magnets, reverse the connections at the battery. Now go outdoors and note the direction of the wind, and if you find the indicator shows it correctly, well and good ; if not, go over the connections again and the way the vane is set in relation to the brass brush or shoe. When everything is correct, screw on the side of the box which was left out, and close all cracks with shellac.

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The pivot of the compass needle must not touch the glass. Oil the bearings of the steel rod in the vane-box occasionally. The only part of the instrument which will wear to any extent is the little brass brush or shoe, but even this will last a year or so. By making eight brass sectors and eight electro-magnets and having nine wires, the vane can be made to show the wind direction to sixteen points of the compass.