public function dir($path, $createMissing = false)
    {
        if (! $this->adapter->isAbsolute($path)) {
            $path = $this->rootPath . $path;
        }
        if (! $createMissing && ! $this->isDir($path, true)) {
            throw new FilesystemException("Cannot find the directory '{$path}'");
        }
        return new Directory($path, $this->adapter);
    }