Figure 8 (fi/. r27) shows the anemometer adopted for United States Signal Service stations. It consists of four hemispherical copper cups mounted on radial arms at right angles to one another, with the planes of their faces vertical and facing the same way. The rods arc fixed on a ver tical axis turning in a tube and having at its lower extremity an endless screw placed in gear with a wheel that moves two concentrically-mounted dials which register the number of revolutions of the cups. The outer dial is graduated with one hundred and the inner dial with ninety-nine divisions. As both dials are moved by the same wheel, but in reverse directions, they will move forward at the same time, but the inner dial will complete one revolution and its zero will be one division beyond the zero of the outer dial when the latter has completed one revolution, the zeros of both dials coinciding at time time the instrument is set in motion. Thus the revolutions of the outer dial are recorded on the inner one. On the outer dial, at equidistant points representing one mile, are pins which depress a spring at the lower part of the dial and close an electric contact, by which the movement of the wind is electrically recorded on the cylin der of the apparatus shown in Figure 9 (pt. 127). The cylinder of the recording instrument is operated by clock-work, and has a rotary move ment and a lateral movement in the line of its axis; the record is imprinted by means of a pencil on a paper diagram placed around the cylinder.
Terchomacrs.—Appliances for measuring the motion of machinery are variously known as tachometers, velocimeters, speed-recorders, speed-indi cators, etc. The tachometer is a contrivance for indicating minute varia tions in the velocity of a machine. Some are purely automatic, while others, in conjunction with their mechanism, are operated by hand.
4 is a device designed to register the speed of any rotating shaft, pulley, or mandrel. To ascertain the number of revolutions of a shaft in a given time, the point of the indicator is placed in the centre of the end of the shaft, and for each hundred revolutions the dial revolves once. Less than one hundred revolutions will be indicated by the pointer, which requires to be placed at the too mark before starting. By a device on the face of the dial, a person may feel with the end of the thumb how often it revolves without looking at the indicator, thus enabling the operator to keep correct time.
Train Speed-recorders.—For ascertaining and recording the speed of railway trains at any given instant special appliances have been devised.
The 'Westinghouse railroad speed-indicator not only records the train speed, but also, by means of automatically-constructed diagrams, exhibits the fluc tuations in the velocity caused by the application of the brakes. The reg istrations are made on a paper drawn similarly to that used at meteoro logical stations to record the velocity of the wind. The heights of the recording lines on the diagrams represent pressures on the accumulator of the speed-indicator, and these pressures are proportioned to the square of the speed.
Dynagraph.—A machine for recording the phenomena occurring to a train in travelling on a railway-track was invented by Professor P. H. Dud ley and called a " dynagraph." The apparatus is placed in a car and uses fourteen diagram recording-pens. The track-inspection record is traced on a continuous roll of paper in a length of too feet wound upon a drum. The paper has various groups of rulings, and the tracings are made by glass tube-pens filled with eosine. The speed of the train is recorded by means of an electrical attachment with a chronometer clock. This attach ment is so arranged as to break an electrical current every second, the cur rent releasing an armature of an electromagnet, with which one of the pens is connected. This moves the pen of an inch horizontally, and produces an indentation in the line which is drawn on the paper. The distance between the indentations indicates the space travelled over in one second. Another pen is so arranged as to make a similar record every ten seconds; still another pen can be used to record minutes. A pen is also so arranged that by an electrical connection it records each revolution of the driving-wheels; another records the mile-posts as they are passed, which is done by an assistant who touches an electrical key at each post. The alignment of the road—that is, the curves and straight lines—is recorded by a pen in a similar way. Next to this pen, and connected with a water meter attached to the feed-pipe of the locomotive, is a pen which records the quantity of water consumed at different times and places. Still another pen is so arranged that an assistant on the locomotive records every shovelful of coal as it is put on the fire. The same pen has been used to record the time that black smoke escaped from the stack. A pen is also provided which records the distance run by the car, and another records the indica tions of an anemometer on the top of the car, while another pen records the surface of the track.