Cannot scroll in UIWebView in iOS

I created a webview programmatically and I am unable to enable scrolling in this view.

How do I enable scrolling?

    UIWebView *webView = [[UIWebView alloc] initWithFrame:CGRectMake(0,40, 325, 1000)];
    webView.contentMode = UIViewContentModeScaleAspectFit;     
    [webView setBackgroundColor:[UIColor clearColor]];
    [webView loadHTMLString:html baseURL:nil];
    [self.view insertSubview:webView atIndex:0];

Thanks In Advance !