The ingenious solution to the candle riddle from last week consists of lighting them both at the same time, one from one end and the other from both. When the second has burned completely, half an hour will have passed; then we light the first candle also from the other end, and from that moment on, when it is completely consumed, a quarter of an hour will have passed. But Ignacio Alonso raises the reasonable objection that a candle that burns at both ends at the same time cannot be in a vertical position, so its combustion time will be altered. That is why the variant with wicks instead of candles is more plausible, since they burn at the same speed in any position, and more homogeneously than candles. (It is not worth splitting the candles in half, because if the midpoint could be determined precisely, a quarter could also be determined and there would be no problem.)
