ss of the gas, which can be applied by the consumer upon his own
premises," said the old gentleman.

"There is little need. The burners should be adjusted to the quality of
gas furnished. If there were any real gain in this method of enrichment,
the gas companies are the parties who could make the most of it: indeed,
many of them do to such an extent as can be made profitable. But
whenever the temperature of the atmosphere falls, the matter added to
the gas is deposited in the pipes, sometimes choking them entirely at
the angles. No: arrange your burners and regulators to suit the gas that
is furnished, demand of the company that it fulfil the law and the
contract in regard to the quality of the gas, and give all gas-improving
machines the go-by.[3]

"Light having, perhaps, been sufficiently considered for the present
needs, we have now to note the effects of the combustion of gas upon the
atmosphere, and through this upon the furnishing of rooms and the health
of the persons living therein," said the chemist, again taking up his
manuscript. "The usual products from the combustion of common
illuminating gas are carbonic acid, sulphuric acid, ammonia and
water-vapor. Every burner consuming five cubic feet of gas per hour
spoils as much air as two full-grown men: it is therefore evident that
the air of a room thus lighted would soon become vitiated if an ample
supply of fresh air were not frequently admitted.

"Remember," said he, looking up from the paper, "that nearly the same
effects proceed from the combustion of candles and lamps of every kind
when a sufficient number of these are burned to give an equal amount of
light. Carbonic acid is easily got rid of, for the rooms where gas is
burned usually have sufficient ventilation near the floor by means of a
register, or even the slight apertures under the doors--together with
their frequent opening--to carry off the small quantity emitted by one
or two burners. But there are other gases which must have vent at the
upper part of the room, while fresh air should be admitted to supply the
place of that which is chemically changed."

Returning to his manuscript, he continued: "The burners which give the
least light, burning instead with a low, blue flame, form the most
carbonic acid and free the most nitrogen. Such are all the burners for
heat rather than light. But the formation of sulphuric acid gas may be
the same in each. In the yellow flame the carbon particles escap