Pronouns in English concerning to things
Sherlock Holmes, The Sign of the Four:
"... I want to find the whereabouts of a steam launch called the Aurora, owner Mordecai Smith, black with two red streaks, funnel black with a white band. She is down the river somewhere..."
I thought that pronouns "He","She" can only be used concerning to human beings. We have to use "It" for animals and things. In the quote Holmes says about launch, so why "She"?