All these requirements of a good
acetylene apparatus have to be sacrificed to a greater or less extent in
portable generators; and since the sacrifice becomes more serious as the
generator is made smaller and lighter in weight, it may be said in
general terms that the smaller a portable (or, indeed, other) acetylene
apparatus is, the less complete or permanent satisfaction will it give
its user. Again, small portable apparatus are only needed to develop
intensities of light insignificant in comparison with those which may
easily be won from acetylene on a larger scale; they are therefore fitted
with smaller burners, and those burners are not merely small in terms of
consumption and illuminating power, but not infrequently are very badly
constructed, and are relatively deficient in economy or duty. Thus any
comparisons which may be made on lines similar to those adopted in
Chapter I., or between unit weights, volumes, or monetary equivalents of
calcium carbide, paraffin, candles, and colza oil, become utterly
incorrect if the carbide is only decomposed in a small portable generator
fitted with an inefficient jet; first, because the latent illuminating
power of the acetylene evolved is largely wasted; secondly, because any
gas produced over and above that capable of instant combustion must be
blown off from a vent-pipe; and thirdly, because the carbide itself tends
to be imperfectly decomposed, either through a defect in the construction
of the lamp, or through the brief and interrupted requirements of the
consumer.
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