Some of the State's rarest and most valuable antiquarian books are available on CD, thanks to a collaboration between Trinity College Library and one of the college's subsidiary companies.

The 25 books available offer historical volumes and invaluable archives such as city directories, almanacs, marriage indexes and maps, all in PDF format. The company plans to make 150 more books available by the end of the year.

Archive CD Books Ireland is part of a worldwide project that has already enjoyed success in England, the Netherlands and Australia. The project makes rare literature widely available and helps preserve the original.

The digital process used to copy the material produces archive preservation standard without harming the originals.

The company expects to be working in the thousands rather than the hundreds in a very short time.

As a British and Irish copyrighted library since the 17th century, Trinity has more than two million books in its archives but these are not generally available to the public.

Mr Brian Donovan of Archive CD Books says that the CDs are faithful reproductions of the original while also being much more accessible.

"The CDs are fully searchable, so material will be far easier to find than ever before. Plus, the books are archive presentation standard, which means they will reproduce perfectly in print or on screen, while the college will be able to put the original away into cold storage."