In New Orleans, the air often retains ninety per cent of the moisture
it is capable of holding; and in cool days at the North, in foggy
weather, the air is sometimes wholly saturated.

When air holds all the moisture it can, without depositing dew, its
moisture is called 100. When it holds three fourths of this, it is
said to be at seventy-five per cent. When it holds only one half, it
is at fifty per cent. When it holds only one fourth, it is at
twenty-five per cent, etc.

Sanitary observers teach that the proper amount of moisture in the air
ranges from forty to seventy per cent of saturation.

Now, furnaces, which are of course used only in winter, receive outside
air at a low temperature, holding little moisture; This it sucks up,
like a sponge, from the walls and furniture of a house. If it is taken
into the human lungs, it draws much of its required moisture from the
body, often causing dryness of lips and throat, and painfully affecting
the lungs. Prof. Brewer, of the Scientific School of New-Haven, who
has experimented extensively on this subject, states that, while forty
per cent of moisture is needed in air to make it healthful, most stoves
and furnaces do not, by any contrivances, supply one half of this, or
not twenty per cent. He says most furnace-heated air is dryer than is
ever breathed in the hottest deserts of Sahara.

Thus, for want of proper instruction, most American housekeepers not
only poison their families with carbonic acid and starve them for want
of oxygen, but also diminish health and comfort for want of a due
supply of moisture in the air. And often when a remedy is sought, by
evaporating water in the furnace, it is without knowing that the amount