Brownrigg also produced a major treatise on salt manufacture. He hoped that improved domestic production could make Britain self-sufficient in this valuable resource thereby improving the fishing industry and economy both in Britain and America. Much of the best quality salt was bay salt produced in France and Spain; the two European powers with whom Britain was most likely to be at war with in the eighteenth century. When a paper based upon his book was read at the Royal Society in June 1748 (whilst the negotiations which were to lead to the peace treaty ending the War of the Austrian Succession were still under way), it was considered the most important paper read there in the last fifty years.