is no mean work that is performed by the Public Carriage Department,
although it is done quietly, smoothly, and for the most part out of
sight of the public. Not a cab, omnibus, or tramway car that plies for
hire in the metropolis--and they average about 16,000 a year--but has
passed stringent tests by experts, and this applies equally to the men
in charge.

Every human precaution that years of experience can suggest is taken to
guard against the passing on the streets of any man or vehicle that
might be a nuisance or a danger in congested traffic. Rigid regulations,
numbering forty in the case of taxicabs, and sixty-two in the case of
motor omnibuses, insist upon details as far apart as adequate brakes and
freedom from noise.

We speak about the perils of the street; but they would be increased,
perhaps tenfold, but for the unobtrusive care of the Public Carriage
Department.

There are other detectives at Scotland Yard than those of the Criminal
Investigation Department--detectives, that is, in all but name--for the
control and supervision of traffic does not end with the issue of an
annual licence.

There are fifty skilled men dotted about London, all holding
certificates of proficiency in motor engineering, who exercise a
constant surveillance. Quick of eye and keen of hearing, they keep
unceasing watch on all public vehicles. An unusual sound as a motor
omnibus passes may tell them something is wrong with the engine.
Thereafter the proprietors are warned not to use the car until the
defect has been remedied. Or they may station themselves unexpectedly at
the gate of a garage, and test the brakes and steering gear of every car
that passes in or out.

That this is no mere formality is shown by the fact that on one morning
an officer stopped no fewer than forty taxicabs from going on the
streets. Indeed, during the last year for which figures are available
officers of the department reported 35,123 vehicles as unfit for use. In
some it was merely a question of noise or a trifling fault easily
remedied. In others the trouble might easily have caused a bad accident.
The principle acted upon throughout the department is that prevention is
better than cure.

Whenever a car of a new type is devised, be it a cab, an omnibus, or a
tramway car, Scotland Yard examines it, and, if necessary, calls in a
consulting expert for advice.

Should the type be suitable, similar vehicles are afterwards examined by
local staffs o