And let me tell you that there was an art in snuffing a candle which required practice and a steady hand.

For if you of the present generation of boys who live in the days of gas, electric lights, spirit lamps, and candles ingeniously made after the analytical experiments of chemists on a material very different from the old-fashioned Russian tallow--if you, I say, were to try and snuff an old candle, the chances are that you would either cut the cotton wick too much or too little, if you did not snuff the light out.

After a time these sources of light would grow lengthy of black, burnt wick, a curious mushroomy, sooty portion would grow on the top, and the flame of the candle would become dull yellow and smoky.

Then, if you cut too little off, the light would not be much improved; if you cut too low down, it was worse; if lower still, you put the light out.

But the skilful hand every few minutes cut to the happy medium, as the Doctor did, and the light burned up fairly white and clear; so that, according to the custom at the cottage, Mrs Burnet could see well to continue reading aloud to her weary husband, this being his one great enjoyment in the calm life on the island.
Now, it seems rather hard on Vince to keep him waiting hungrily at the door while the writer of this little history of boy life runs away from his narrative to begin prattling in print about candles; but what has preceded these lines on light, and the allusion to chemistry, does ask for a little explanation, for many of you who read will say, What can chemistry have to do with tallow candles?
A great deal.