The postmasters had been allowed to receive their correspondence free of postage; but Allen soon found that the privilege was being abused. The covers addressed to them would contain letters not for themselves alone but also for their neighbours in trade. Indeed the neighbours' letters would predominate, and, ordinarily, the address was a mere subterfuge. To check this abuse Allen established a rule that when addressed to postmasters none but single letters--letters without enclosures, were to pass free, and that all others were to be charged with full postage. The postage, however, was to be afterwards remitted in the case of any postmaster who should make oath that the letters in respect to which he claimed remission were on his private business. Here again Allen's belief in the efficacy of an oath was rudely shaken. The number and magnitude of the claims made upon him from Lancaster had arrested his attention, and he had laid them aside to be examined at leisure. Meanwhile the explanation came in a curious manner. He received a circular from a man of the name of Bracken asking him to subscribe towards the publication of a book relating to the treatment of horses.[46] This circular, as announced in the document itself, was being issued to all the postmasters in the kingdom; and it was in his capacity of postmaster of Bath that Allen received it. It further announced that answers should be sent under cover to the postmistress of Lancaster, the reason given being that they would thus escape postage. [46] The book was afterwards published--_The Gentleman's Pocket-Farrier_, by Doctor Henry Bracken of Lancaster, 1735.