The University of Leicester collected the directories

The digitisation process has been undertaken by the University of Leicester, using a grant of �335,000 from Lottery funds.

It could prove a useful tool for family historians and academics.

According to archivist Ian Clarke, who worked on the project, the directories were the Yellow Pages of their day.

Fuzzy logic

"They were like the Yellow Pages but with a lot more information, including census details, eclipses and even tables showing tide times," he told BBC News Online.

People tracing their family history would be able find out that their great grandfather was a plumber for instance Ian Clarke, Archive Quest

The website uses a search engine developed by document management firm ZyLab.

Technology known as fuzzy logic allows users to search documents for specific words, even if the term is spelt differently in the document.

The system makes it easier to search manuscripts for specific details, and avoid the costly procedure of turning them into electronic text.

Previously the system has been used by the FBI on cases such as the Enron investigation, which trawled through nine million documents.

The website, historicaldirectories.org, has already proved very popular and has had users from as far afield as Australia and Canada.

Grandfather's job

It has so far put 330,000 documents from some 643 directories online.

Mr Clarke, a senior technologist at the digital imaging firm Archive Quest, believes the website will serve a variety of needs.

"People tracing their family history would be able find out that their great grandfather was a plumber for instance," he said.

For anyone restoring an old house the archives could contain valuable insights into how the original land was divided.