o sign
a deed or other writing, especially a sealed writing, his authority
must also be equally great. In executing a deed therefore his
authority must be in writing under seal, and when the deed is
recorded, the agent's written authority should also be recorded; this
is the usual practice. If this is not done, some person who afterward
wished to purchase the land might object because the recorded title
was defective.

A particular usage or custom also affects an agent's powers. If the
principal confers on him authority to transact business of a
well-defined nature, bounded by well-defined usage and customs, the
law presumes the agency was created with reference to them. This
protection affects agents and third persons alike, the latter
therefore who act in good faith in such dealings are protected against
secret limitations of which they had no notice.

An agent has no authority to purchase his principal's property. To do
this, in a sense, would be to purchase of himself. The temptation to
do this is sometimes very great, too great for him to withstand, and
so he resorts to a crooked method for accomplishing his end. He sells
the property to another party who afterward sells it back to him. The
worst violators of this principle have been railway receivers, who
have taken advantage of their position to get control of the property
entrusted to them at a sum much less than its real value. Such sales
can be set aside by proper legal procedure. By the modern rule they
are not void but are voidable, that is, can be set aside if the
creditors or other interested parties wish to do so.

Whenever therefore one deals with a general agent and his authority is
disputed, unless there be restrictions known to the person dealing
with him, the liability of his principal turns on the answer to the
general question, what authority do general agents like himself have.
This is simply a question of fact, to be determined like every other
question of fact by the court in which the controversy is pending.

Another way of rendering a principal liable for the act of his agent
is by ratifying it. Suppose A professed to be the agent of B in
building a house for C, and built it so badly that C sued B to recover
damages, whose defense was, that A was not his agent. Suppose,
however, that B accepted payment for the house, this would be a
ratification of A's authority to act for B even if he did not have
proper authority in the beginning. Suppo