Mutton-suet, chop-parings, and other clean, wholesome fat can be bought wholesale for less than fivepence per pound. It would cost above three times as much as this to bring the fat nodules of the Thames mud to as near an approach to butter as this sort of fat. Therefore the Thames mud-butter material would be three times as costly as that obtainable from the butcher. While the supply of mutton-suet is so far in excess of the butter-making demand that tons of it are annually used in the North for lubricating machinery, we need not fear that anything less objectionable—i.e., more costly to purify—will be used as a butter substitute.
LUMINOUS PAINT.
The sun is evidently going out of fashion, and is more and more excluded from “good society” as our modern substitute for civilization advances. “Serve him right!” many will say, for behaving so badly during the last two summers. The old saw, which says something about “early to bed and early to rise” is forgotten: we take “luncheon” at dinner-time, dine at supper-time, make “morning” calls and go to “morning” concerts, etc., late in the afternoon, say “Good morning” until 6 or 7 P.M.; and thus, by sleeping through the bright hours of the morning, and waking up fully only a little before sunset, the demand for artificial light becomes almost overwhelming. Not only do we require this during a longer period each day, but we insist upon more and more, and still more yet, during that period.
The rushlight of our forefathers was superseded by an exotic luxury, the big-flame candle made of Russian tallow, with a wick of Transatlantic cotton. Presently this luxurious innovation was superseded by the “mould candle;” the dip was consigned to the kitchen, and the bloated aristocrats of the period indulged in a pair of candlesticks, alarming their grandmothers by the extravagance of burning two candles on one table. Presently the mould candle was snuffed out by the composite; then came the translucent pearly paraffin candle, gas light, solar lamps, moderator lamps, and paraffin lamps. Even these, with their brilliant white flame from a single wick, are now insufficient, and we have duplex and even triplex wicks to satisfy our demand for glaring mockeries of the departed sun.
Some are still living who remember the oil lamps in Cheapside and Piccadilly, and the excitement caused by the brilliancy of the new gas lamps; but now we are dissatisfied with these, and demand electric lights for common thoroughfares, or some extravagant combination of concentric or multiplex gas-jets to rival it.
The latest novelty is a device to render darkness visible by capturing the sunbeams during the day, holding them as prisoners until after sunset, and then setting them free in the night. The principle is not a new discovery; the novelty lies in the application and some improvements of detail. In the “Boy’s Own Book,” or “Endless Amusement,” of thirty or forty years ago, are descriptions of “Canton’s phosphorus,” or “solar phosphori,” and recipes for making them. Burnt oyster-shells or oyster-shells burnt with sulphur, was one of these.
Various other methods of effecting combination between lime or baryta with sulphur are described in old books, the result being the formation of more or less of what modern chemists call calcium sulphide and barium sulphide (or otherwise sulphide of calcium or sulphide of barium). These compounds, when exposed to the sun, are mysteriously acted upon by the solar rays, and put into such a condition that their atoms or molecules, or whatever else constitutes their substance, are set in motion—in that sort of motion which communicates to the surrounding medium the wavy tremor which agitates our optic nerve and produces the sensation of light.
Until lately, this property has served no other purpose than puzzling philosophers, and amusing that class of boys who burn their fingers, spoil their clothes, and make holes in their mothers’ table-covers, with sulphuric acid, nitric acid, and other noxious chemicals. The first idea of turning it to practical account was that of making a sort of enamel of one or the other of these sulphides, and using it as a coating for clock-faces. A surface thus coated and exposed to the light during the day becomes faintly luminous at night.
Anybody desirous of seeing the sort of light which it emits, may do so very easily by purchasing an unwashed smelt from the fishmonger, and allowing it to dry with its natural slime upon it, then looking at it in the dark. A sole or almost any other fish will answer the purpose, but I name the smelt from having found it the most reliable in the course of my own experiments. It emits a dull, ghostly light, with very little penetrating power, which shows the shape of the fish, but casts no perceptible light on objects around.