Translate the following sentence into Chinese.
So it seems that pigeons also have some extra sense of directions to use when they cannot see the sun.
With a strong magnet close by, anything like a magnetic compass can no longer tell about the earth's weak magnetic field.
Seeing-eye dogs learn never to cross a busy road when cars are coming, even if their masters command them to do so.
Pigeons have a natural instinct to return home, even if they are very far away and the trip is hard or dangerous.
When a dog has been properly trained, he will always lead his blind master in the right direction and keep him out of danger.
With this skill he can be very useful in tracking down lost people or criminals.
Men utilize this homing instinct to send messages on small pieces of paper which are fastened to the pigeons’ backs or legs.
Horses that are used for guard or police duty must learn never to be frightened of noises, traffic, and other disturbances.
Pigeons have been known to fly as fast as 75 miles an hour and to cover distances of 500 to 600 miles.
To teach a dog this skill, the master makes a simple trail by walking some distance in a straight line.
Therefore, it is necessary for those people who train them to be very patient and understanding.
To test the idea, one group of ten pigeons had strong little bar magnets attached to their backs.
What happens when the sky is darkly overcast by clouds and no one can see where the sun is?
One way to test that idea would be to see if a pigeon's sense of direction can be fooled by a magnet attached to its back.
But on very overcast days those clock-shifted pigeons are just as good as normal pigeons in starting out in the right directions.
We have talked about one of the more complex experiments that lead to the belief that homing pigeons can tell directions by the sun.
The same experiment we talked about has been repeated many times on sunny days and the result was always the same.
Naturally, people have wondered whether pigeons might have a built-in compass -- something that would tell them about the direction of the earth's magnetic field.
They have picked a direction that would be correct for the position of the sun and the time of day according to their shifted clocks.
I punished him several times, and, indeed, led him to the conviction that it was wrong to steal; but he could never resist the temptation.