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isolated houses to investigate its action on rats under natural conditions. The
investigation should be made by some one familiar with the use of the gas.

Cost of Disinfection.

   I.—Disinfection of clothes.—As we have stated above, an air-tight godown
must be built with arrangements for letting the gas play on the clothes for, say,
fifteen minutes and then turning off the supply of gas to allow of safe entry to the
building. This would be necessary if the clothes are to be returned to their
owners in a reasonable time. The advice of an engineer is requisite for the con-
struction of the godown as the danger from the gas is not to be underrated. The
price of the chemicals is slight.

     The cost of potassium cyanide (98—100 per cent.) is 1 shilling per lb. for
28 lbs., or 99 shillings a cwt. if bought in bulk (Merck's quotation). The cost of
sulphuric acid is 1d. (one penny) per lb. if carboys are bought (Baird &
Tatlock's quotation).

     Suppose the room was of 1,000 cubic feet capacity and moderately air-tight, 7½
ozs. of potassium cyanide and 15 ozs. of sulphuric acid would be required.
The total cost of chemicals for disinfection would be between 6 pence and 7 pence
plus the pay of a supervisor. China vessels to hold the chemicals would last
indefinitely.

       II.—Cost of disinfecting houses.—We have got a machine adapted for
experiments in single rooms and we could use it for experiments on houses with
natural burrows. Some extra lengths of tubing might be necessary, but the cost
would not be great.

      The conclusion then is that so far as disinfection of clothes is concerned we
have in hydrocyanic acid gas a very cheap and efficient pulicide. With a specially
constructed godown, it would be possible to deliver over to their owners clothes
absolutely free of fleas in half-an-hour. There would be no damage to fabrics.
If proper precaution is taken and an experienced man acts as supervisor no
accident should occur.

       With regard to the disinfection of houses the conclusions arrived at are not
so satisfactory. We desire permission to use this gas in isolated huts with natural
burrows. With artificially constructed burrows good results have been obtained.
If as satisfactory results can be got with natural burrows we have an efficient
means of clearing houses of plague rats and fleas. But the means are not without
danger. This danger could be largely guarded against in isolated houses with a
clear space round them, or in an aggregation of houses with a clear space round
them, as in a village, if evacuation of the houses could be insisted on till such time
as occupation be declared safe. In crowded localities, as in tenements in cities,
the danger is too great to permit employment of the method.