Limelight is therefore now but little used in this country, as the majority of large halls are equipped with the electric
current, and for smaller buildings it is deemed unnecessary and too expensive.
Acetylene is undoubtedly the illuminant most in favour next to electric light, as the light is brilliant enough to illuminate a picture 12 feet in diameter at a distance up to, say, 30 feet from the screen, and this suffices in a large majority of cases, and acetylene is comparatively cheap, and reasonably simple to work.
Incandescent-gas is often employed for small class-rooms and is fairly effective for a picture not exceeding 9 or 10 feet in diameter, and the same can be said of the same type of burner heated by methylated spirit.
Paraffin-oil is the poorest of all present-day forms of lantern illuminants. The flame is large, impairing the definition, yellow in colour, uneven in illumination, liable to smoke and smell, and barely equal to incandescent gas in illuminating power.
It is therefore going gradually out of use in this country, but in out-of-the-way places, especially abroad, it is sometimes the only practicable light, and is therefore still employed from the best of all reasons, necessity.
It is not the intention of the author to give precise working instruction for all and every variety of the above illuminants as manufactured by different firms. For such the reader must be referred to the directions usually issued by the makers themselves, but a general description of the various types offered for choice will not be out of place, and it will be more convenient to begin with the poorest, viz. paraffin-oil, and finish with the most perfect, the electric arc.