Electrical Jottings

Mt Benger Mail, 28 September 1938, Page 4

Electrical Jottings

BY LUMENS What is a lumen? Rarely does one find a word about it in modern dictionaries', for, simple though it be, a lumen has for long hidden its light under a technical bushel. A lumen is to light what pints are to milk; it is the unit used to express the amount of light emitted by a lamp. A common candle sheds about 12 of these lumens; a 100 watt coiledcoil electric lamp about 1300 of them.

You all know the importance of comfortable seeing; how it helps you to enjoy many of the good things of life; what anguish is caused when seeing is defective. A little thought and you realise that seeing operates by means of the light that is about you. Your optical system, marvellous mech- , anism though it be, will not function properly if the lighting is not within the necessary working limits. In brief, there must be sufficient lumens shed on the task, be it reading, sewing, writing or any similar visual work, and most important, these lumens must arrive in such a manner that their source, the brilliantly glowing lamps, cannot be seen even just a little by the eyes. Naked lamps cause glare and continued exposure to glaring lights soon blights the eyes. Was it not a famous poet who once wrote—“He saw, but blasted with excess of light, closed his eyes in endless night. ’ ’ You can have too much glaring light and too little diffused light’. Different strengths of lumens are required for different tasks of seeing. For sitting and talking a relatively small number of lumens will ensure ease of seeing, but for reading, especially small newsprint, plenty of iluminaltdon is required. One has seen people reading in a corner of a room, darkly decorated, lighted by a single 60 watt lamp shrouded by a dust-engrimed silk or parchment shade. Certainly the bare lamp is hidden, but the number of lumens reaching the print is far too small for the eyes ito sort out all the little shapes which form the printed page, and do it with any degree of comfort. Directly under the centre fitting there is often sufficient light but it is not always convenient to sit in the middle of the room.

A room, to be adapted for perfect illumination, should have light coloured walls and ceiling; where possible the floor covering should also be of a light tone. For reading, writing, etc., two or more correctly designed portable stand almps, such as the ‘Better Light— Better Sight” lamps should be used; for general lighting a suitable central fitting or wall brackets is sufficient. For the average room a 100 watt 1 lamp in the central fixture and similar sizes in the portable lamps will ensure at all times a sufficient quantity of lumens where 'and when needed. And should you think that four or five lights in one room is too extravagranit, let me tell you that American homes, hotels and so forth often have 14 lights per room. And contrary to popular belief, electricity is by no

means cheap in the States. Naturally all .these lamps are not operating together, they are there for your convenience to be used as required. f i An electrical machine has been invented which “tells the time” at 6 second intervals in a loud clear voice. The machine, about, 34 inches long, has two small endless belts of sound film, with the hours recorded on one and minutes on the other. A device known as an optical unit, containing a tiny light and an “electric ;eye ’ * is pulled back and forth along the three films by a twentieth horse-power motor similar to those which run electric clocks. The light fluctuates as it passes over the sound tracks in the film: the fluctuations are caught by the “eye” and converted into electric vibrations; the vibrations create the sound and the words come out distinctly through an amplifier.