An inspection of the piles is advisable every two days. Were a larger reservoir employed and the velocity of flow moderated, the interval might be still longer.
The four elements in tension alternately charge two series of accumulators each containing three elements. This arrangement allows the use of two kinds of lamps, 6 volt ones in the cellar and small rooms, and 10 volt ones in the dining-room and office.
The cellar lamp is so arranged that it is lighted by opening the door, and extinguished by closing it. Aside from the lamps just mentioned, another is arranged for lighting a dark ante-room, and which lights up for three minutes, only, whenever a button near the door is pressed.
The use of accumulators and flowing piles presents the following advantages: (1) Convenience, the apparatus being always ready to furnish light upon turning a tap; (2) Ease of keeping in repair and of supervision, the flow and the dimensions being capable of regulation so that the consumer need look after the piles only at irregular intervals. (3) Better utilisation of the products as a result of the use of a pencil of zinc instead of wide plates. The surface attacked is reduced to the dimensions that are strictly necessary for the production of a current, and local action is thus diminished. On the other hand, the active liquor is not thrown away until completely exhausted. (4) Quality of the light. This remains steady during the entire time of the lighting, without any manipulation of the pile or any special appliance.
A few hints may be culled from Preece’s lecture on Domestic Electric Lighting, read before the Society of Arts last session.
Makers of lamps seem to consider that there is great credit in securing long life. Unfortunately, glow lamps deteriorate sadly with age. The carbon wastes imperceptibly away, and we are scarcely conscious of the fact that, after 200 or 300 hours, the lamp gives only half the light it did at first. The fact is lamps last too long. The price of a lamp should be such that we could afford to give them a short and merry life. Long life is therefore an objection.
Lamps fail in giving their light occasionally from having an imperfect vacuum. This is very easily detected by feeling the globe. If the vacuum is bad it gets quite hot. Occasionally, but very rarely, lamps explode with a loud report when the current is first put on. This is, perhaps, due to a slight leakage of air making an explosive mixture with the residual gas.
At the present moment, both the nomenclature and the efficiency of glow lamps are in a very unsatisfactory state, and we are buying pigs in a poke at a very high price.
Considerable difference of opinion exists as to the character of the globe enveloping the carbon filament. Some like them clear, some like them ground; others envelope them in shades, or make the globe of a beautiful opal glass. It is very objectionable to have the optic nerve irritated by a brilliant glowing filament; but it is equally absurd to produce a good thing and then strangle it. Grounding and shading mean loss of light. Lamps can be placed so high that they need not affect the eye, and if they do, the light can be so reflected as to be useful elsewhere. The art of lighting a room is to flood it with light without the delicate eye being offended with the direct rays from the source of light.
Switches to turn the lamps on and off are a source of great trouble in a house. As a rule, they are cheap and nasty. When fixed away from the lamps, they introduce into the circuit additional resistance, and therefore waste energy, but they are distinctly serviceable when they are fixed outside the door of a room, so that you can light it before you enter it.