This backtrace appears to be of no use.

此回溯跟踪似乎没有用处。

If we make black-lead very hot, it will burn. But it will burn very slowly-so slowly that it would be of no use for making a fire.

如果把石墨弄得特别热，石墨就会燃烧起来，但是燃烧得特别慢，不能用它生火。