they must not
trespass upon his domain. That he is acting well within his rights in
doing this is conceded by legal authorities.

Hard to Catch Offenders.

But, suppose the alleged trespass is committed, what is the property
owner going to do about it? He must first catch the trespasser and this
would be a pretty hard job. He certainly could not overtake him, unless
he kept a racing aeroplane for this special purpose. It would be
equally difficult to identify the offender after the offense had been
committed, even if he were located, as aeroplanes carry no license
numbers.

Allowing that the offender should be caught the only recourse of the
realty owner is an action for damages. He may prevent the commission of
the offense by force if necessary, but after it is committed he can only
sue for damages. And in doing this he would have a lot of trouble.

Points to Be Proven.

One of the first things the plaintiff would be called upon to prove
would be the elevation of the machine. If it were reasonably close to
the ground there would, of course, be grave risk of damage to fences,
shrubbery, and other property, and the court would be justified in
holding it to be a nuisance that should be suppressed.

If, on the other hand; the machine was well up in the air, but going
slowly, or hovering over the plaintiff's property, the court might be
inclined to rule that it could not possibly be a nuisance, but right
here the court would be in serious embarrassment. By deciding that it
was not a nuisance he would virtually override the law against invasion
of a man's property without his consent regardless of the nature of the
invasion. By the same decision he would also say in effect that, if one
flying machine could do this a dozen or more would have equal right to
do the same thing. While one machine hovering over a certain piece of
property may be no actual nuisance a dozen or more in the same position
could hardly be excused.

Difficult to Fix Damages.

Such a condition would tend to greatly increase the risk of accident,
either through collision, or by the carelessness of the aviators in
dropping articles which might cause damages to the people or property
below. In such a case it would undoubtedly be a nuisance, and in
addition to a fine, the offender would also be liable for the damages.

Taking it for granted that no actual damage is done, and the owner
merely sues on account of the invasion of his property, how is t