of defending his possessions.

Whether the right has been fully acquired is not always easily
determined. Suppose one claims a right of way over another's land, and
the right is disputed. How often has he traveled that way? Has the
other person known of his going and said nothing? Again, suppose a man
sells another a piece of his farm away from a road, the law presumes
that he intended to grant or permit the buyer to have ingress and
egress to his land, otherwise he would not have purchased. This is
called a way of necessity. Can the purchaser choose any outlet he
pleases? The law says he must exercise reasonable discretion in making
his selection.

When a way has been acquired by such use, the law is strict in
confining the gainer in the use of it. Thus A buys a piece of land of
another for the purpose of erecting a house thereon. The use of the
way thereto must be confined to A and his family, friends and those
who come to see him on business. Suppose A should decide to divide it
into building lots, which would require a greatly increased use of the
way. This could not be done without a new agreement with the seller.
Again, a tenant cannot by any use of the land acquire a right therein
that will continue beyond his lease. If he had a long lease, say
thirty years, and could gain a prescriptive right by an adverse use of
fifteen or twenty years, he would, if gaining any prescriptive rights,
be obliged to give them up at the end of his tenancy. In claiming a
right of way the use need not be exclusive. Other persons may also use
the way with the same claim of right.

The owner of land has no natural right to light or air and cannot
complain that either has been cut off by the erection of buildings on
adjoining land. He may, however, acquire, by grant or some other way,
a right to have light and air enter a particular window, or other
place, without interruption by the owner of adjacent land. Nor can he
acquire a right to light and air across another's land for his own
house by simply erecting it on the edge of his own land while the
adjoining land is unoccupied. To erect windows on that side is not an
adverse use of the land adjoining. But a person may gain a right to
light and air by presumption, and if one has acquired the right to
maintain a window in a specified place he loses his right by closing
it up and opening another of a different size in another place. And
the same thing happens to one who tears down his h