lights are required for long periods, no doubt they are economical.
Burners of the Bower or Wenham class would be worth adopting for main
street or open space lighting in important positions; but when we consider
that, with the fifty-four hours' system in workshops, artificial light is
only wanted, on an average, for four hundred hours per annum, we may take
it as certain that, at the present prices of regenerator burners, they are
a bad investment for use in ordinary work. We must not forget that the
distance of the burner from the work is a vital point of the cost
question; and, for all except large spaces, requiring general
illumination, a common cheap burner on a swivel joint has yet to meet with
a competitor. Do not think I am old-fashioned or prejudiced in this
matter. It is purely a question of figures; and my condemnation of
regenerator burners applies only to the general requirements in ordinary
engineering and other work shops where each man wants a light on one spot
only.

Some people think that clear glass does not stop any light. This is a
great mistake, as you will find it quite easy to throw a distinct shadow
of a sheet of perfect glass on a white paper, as I will show you. Opal and
ground glass throw a very strong shadow, and practically waste half the
light. It is better to have a white enameled or whitewashed sheet-iron
reflecting hood, which will protect the sides from wind, if such an
arrangement suits other requirements.

I have endeavored in the engraving below to reproduce the shadows thrown
by different samples of glass. This gives a fair idea of the actual loss
of light involved by glass shades.

When lights are suspended, it is a common and costly fashion to put them
high up. When we consider that light decreases as the square of the