Take the sentence, "The veterinarian took pride in her work." The pronoun
her refers back to veterinarian, the subject of the sentence. In this context, veterinarian
is the pronoun" antecedent, the word that the pronoun refers back
to in the sentence. Usually, the antecedent comes before the pronoun in the
sentence. In all cases, the pronoun and its antecedent must agree in number
and gender.

In the following sentences, the antecedent is italicized, and the pronoun
is underlined.
The flag has lost its colors over these two years. (singular antecedent
and pronoun)
Our teachers surely know their subjects well. (plural antecedent
and pronoun)
Dogs know their capabilities. (plural antecedent and pronoun)

Simple Science

Hot water Heating

Heat:
The heated air which rises from furnaces is seldom hot enough to warm large buildings well; hence furnace heating is being largely supplanted by hot-water heating.

The principle of hot-water heating is shown by the following simple experiment. Two flasks and two tubes are arranged as in Figure 15, the upper flask containing a colored liquid and the lower flask clear water. If heat is applied to B, one can see at the end of a few seconds the downward circulation of the colored liquid and the upward circulation of the clear water. If we represent a boiler by B, a radiator by the coiled tube, and a safety tank by C, we shall have a very fair illustration of the principle of a hot-water heating system. The hot water in the radiators cools and, in cooling, gives up its heat to the rooms and thus warms them.

In hot-water heating systems, fresh air is not brought to the rooms, for the radiators are closed pipes containing hot water. It is largely for this reason that thoughtful people are careful to raise windows at intervals. Some systems of hot-water heating secure ventilation by confining the radiators to the basement, to which cold air from outside is constantly admitted in such a way that it circulates over the radiators and becomes strongly heated. This warm fresh air then passes through ordinary flues to the rooms above.

In Figure, a radiator is shown in a boxlike structure in the cellar. Fresh air from outside enters a flue at the right, passes the radiator, where it is warmed, and then makes its way to the room through a flue at the left. The warm air which thus enters the room is thoroughly fresh. The actual labor involved in furnace heating and in hot-water heating is practically the same, since coal must be fed to the fire, and ashes must be removed; but the hot-water system has the advantage of economy and cleanliness.