Looking For Something

Late at night, a drunk was on his knees beneath a street-light, evidently looking for something.
A passer-by, being a good samaritan, offered to help.
- What is it you have lost ? he asked.
- My watch, replied the drunk. It fell off when I tripped over the pavement.
The passer-by joined in the search but after a quarter of an hour, there was still no sign of the watch.
- Where exactly did you trip ? asked the passer-by.
- About half a block up the street, replied the drunk.
- Then why are you looking for your watch here if you lost it half a block up the street ?
The drunk said :
- Because the light's a lot better here.