The effect of air pollution on the durability of book papers has long been recognized. A number of authors have attempted retrospective studies of paper permanence as a function of storage conditions for identical copies of books in differenct libraries. Among these studies, that of Hudson is particularly suitable for statistical analysis of the significant of the experimental results. In his study, surfacepH was determined for the paper of 25 books varying in age from 150-350 years. The books were in the collections of the Portico Library, subject to the polluted urban atmosphere of Manchester, England; and the Chatsworth Library, in open country, some 20 miles east at a not normally polluted site. The author concluded that atmospheric pollution was a cause of the lower pH values obtained particularly at the book edges for samples from Manchester. It is the purpose of this note to test the statistical significance of this conclusion. -- AATA