3. (Redwood.) Quassia chips (small), 1⁄4 oz.; water, 1 pint; boil 10 minutes, strain, and add of treacle, 4 oz. “Flies will drink this with avidity, and are soon destroyed by it.”
4. Black pepper, 1 teaspoonful; brown sugar, 2 teaspoonfuls; cream, 4 teaspoonfuls. See below.
Fly Powder. The dark grey-coloured powder (so-called ‘sub-oxide’) obtained by the free exposure of metallic arsenic to the air. Mixed with sweets, it is used to kill flies.
Fly Water. See Fly Poison (above).
FOG. The influence of very intense foggy weather upon the death-rate is well illustrated by a reference to the Registrar-General’s returns for 1873. From the 8th to the 12th of December of that year an unprecedently thick fog prevailed in London. The mortality in the metropolis for the week ending December 6th was twenty-three persons per thousand; in the week following, during which the fog occurred, the death-rate rose to twenty-seven; and in the week after that, when the full effects of the fog could be estimated, the deaths were found to be thirty-eight in the thousand. In the same periods the deaths from phthisis and diseases of the respiratory organs were respectively 520, 764, and 1112. That this increased death-rate was not the result of the inclement weather by which the fog was accompanied is evidenced by the circumstance that in large provincial towns, where the weather was equally severe, but in which no fog occurred, the increase in the mortality, when compared to London, was slight.
The mean of the deaths registered in London, in the two weeks ending December 20th, showed an increase of 41 per cent. upon the number returned in the first week of the month; whilst during the same date the deaths in seventeen large English towns were only 8 per cent. This fatal fog occurred during the London cattle-show week, and killed a great number of the animals sent for exhibition.
In a specimen of the air of Manchester, obtained during the visitation of that city by a very dense fog, Dr Angus Smith discovered it contained a diminished amount of oxygen when compared with a favorable sample of air.
FOILS. These are thin leaves of polished metal, placed under precious stones and pastes, to heighten their brilliancy, or to vary the effect. Foils were formerly made of copper, tinned copper, tin, and silvered copper, but the last is the one wholly used for superior work at the present day.
Foils are of two descriptions:—white, for diamonds and mock diamonds, and—coloured, for the coloured gems. The latter are prepared by varnishing or lacquering the former. By their judicious use the colour of a stone may often be modified and improved. Thus, by placing a yellow foil under a green stone that turns too much on the blue, or a red one under a stone turning too much on the crimson, the hues will be brightened and enriched in proportion.
Prep. 1. (Crystal, Diamond, or White foil.)—a. This is made by coating a plate of copper with a layer of silver, and then rolling it into sheets in the flatting mill. The foil is