As the industry advanced the methods of marking improved. At the present
time a mark in the ear made of metal is most commonly used. These are in
many different styles such as narrow bands looped into the edge or in
the form of a button fastened through the ear.
Tags are lettered with owner’s name and address and numbered, which
serves not only as a mark for identification of ownership but as a means
of keeping a record of each animal by number; also in making health
tests before shipping from one point to another.
How is Glue Made?
The best quality of glue is obtained from fresh bones, freed from fat by
previous boiling, the clippings and parings of ox hides, the older skins
being preferred; but large quantities are also got from the skins of
sheep, calves, cows, hares, dogs, cats, etc., from the refuse of
tanneries and tanning works, from old gloves, from sinews, tendons and
other offal of animal origin.
By a process of cleaning and boiling the albuminoid elements of the
animal matter are changed into gelatine. This, in a soft, jelly-like
state, constitutes “size;” dried into hard, brittle, glassy cakes,
which, before use, must be melted in hot water, it forms the well-known
glue of the joiner, etc.
When a solution is mixed with acetic or nitric acid it remains liquid,
but still retains its power of cementing; in this state it is called
liquid glue.
Marine glue is a cement made by dissolving India rubber in oil of
turpentine or coal-naphtha, to which an equal quantity of shellac is
added.
Why does a Hot Dish Crack if We Put Ice Cream in It?
If we take a hot dish and put ice cream in it, it cracks because the
dish when hot has expanded. All the tiny particles that make up the dish
have absorbed some heat and have expanded. When the ice cream is put in
the particles composing the inside of the dish are cooled off and begin
to contract, while the outside particles have not cooled and they pull
away from each other, causing the dish to crack.