"http : //" is missing for the "Manoj Nahar" link.

For more tips on the historical maps layer (and the other three new layers), read Google Earth Blog:

gearthblog.com/blog/archives/2 ...

Thanks Haochi, fixed!

Cool stuff.

If you've never visited the Rumsey Collection,
davidrumsey.com/
this specialty database is currently home to more than 13,600 digitized maps. According to the Rumsey site, Google Earth is providing access to 16 maps.

Learn More:
+ An interview with David Rumsey
sfgate.com/cgi-bin/article.cgi ...

+ All About the David Rumsey Map Collection
resourceshelf.com/2003/07/16/a ...

Btw, if digital globes are of interest. Take a directionsmag.com/article.php? ... look at a new plug-in from SkylineGlobe (U.S. only) at this point and NASA's World Wind.

skylineglobe.com/
Overview:
resourceshelf.com/2006/10/09/v ...

Review:
directionsmag.com/article.php? ...
Note: Allows access to KML/KMZ files.

WorldWind (open source, volunteer project)
worldwindcentral.com

Special note to the What's New section:
worldwindcentral.com/wiki/Worl ...

Can now import KML/KMZ files
The Add-Ons Blog
worldwindadd-ons.blogspot.com/

and the fact that you can use MS Virtual Earth with it.
worldwindcentral.com/wiki/Add- ...

Is there a way to change the "opacity" of theses layers? (from 0% to 100%...)