The law of copyright was made in 1814 (54 Geo. III. c. 156). It enacted that an author should possess a right in his work for life, or for twenty-eight years. If he died before the expiration of twenty-eight years, the residue of the right passed to the heirs.
By Talfourd's or Lord Mahon's Act (1842) the time was extended to forty-two years, and at least seven years after decease: for example, if the time unexpired exceeds seven years, the heirs enjoy the residue; if less, the heirs claim seven years.
In the first case eleven copies of the work had to be given for public use; by Lord Mahon's Act the number was reduced to five: i.e. one to each of the following institutions, viz. the British Museum, the Bodleian
(Oxford), the University library (Cambridge), the Advocates' library (Edinburgh), and the library of Trinity College (Dublin).
The six omitted are Sion College, the Scotch Universities of Glasgow, Aberdeen, and St. Andrews, and King's Inn (Dublin).
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
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