Sydney  - An Australian woman who set at least 21 forest fires on Adelaide's outskirts on the hottest days of 2007 was sentenced Tuesday to 13 years in prison.

   Helen White, 45, is one of few women convicted of setting fire to forests.

   In February, forest fires outside Melbourne killed 173 people, destroyed more than 1,800 houses and left 7,500 people homeless.

   Unlike those fires, some of which were also caused by arson, the blazes caused by White caused little damage.

   Judge Michael Boylan said without White's guilty plea, he would have sent the mother of two young children to prison for 18 years.

   White is to become eligible for parole in 2018.