H. G., Melbourne, Victoria, Australia, writes: "Referring to your answer to a correspondent yon say that you prefer artificial heat for local ventilation. Where should a gas jet be inserted to give the best results? Would it answer just as well if it is put in the upcast pipe on the bottom floor or any of the intermediate floors, and would not an atmospheric burner be the best to use, as they give off a much greater heat ?"

[As the efficiency of ventilation by artificial heat depends mainly upon the height of the column of heated air, it is obviously important to put the burner or other source of heat as low as possible, for the same reason that a fire in the basement usually draws much better than one on the top floor.

As to the use of an atmospheric or Bunsen burner, we should say that provided the gas is completely consumed, which is the case when the flame is clear and smokeless, it makes little or no difference what kind of a burner is used, the total heat resulting from the combustion will be the same.

The ordinary burner is more readily obtained and has the incidental advantage that its light shows more plainly than the other whether it is burning or not. It if true that it radiates more heat than the Bunsen burner and that the heat thus radiated is most of it lost as far as heating the air currents is concerned, but we should not think the difference sufficient to warrant any extra trouble or expense in procuring atmospheric burners

The ordinary burner is very easily made into an atmospheric one by slipping over it a slightly tapered sleeve, say 3 inches long and enough larger than the burner to permit a current of air to flow up all around it, the upper and smaller end of the sleeve extending slightly above the top of the burner. Such an attachment, called "Dare's burner," is, or was, patented in this country and could probably be obtained of any dealer in gas fixtures.

Our correspondent could readily determine the relative efficiency of different burners in producing air currents by a very simple experiment whose results we should be pleased to learn and publish. Let him place in or over the outlet of his vent pipe, or in any place where it can be seen and at the same time moved by the current of heated air, a wheel of thin metal, pasteboard, or even of paper, then if he will count the number of turns it makes in say one minute with each kind of burner, he will learn which of them gives the strongest draft.]