The letter is a first hand eye-witness description and sketch of John Blenkinsop’s ‘Salamanca’ steam locomotive, 1812. This locomotive predated Stephenson’s Rocket by 17 years. Blenkinsop (1783-1831) was one of the pioneers of the locomotive and was engaged in the Middleton collieries near Leeds. In 1811 he obtained a patient for a double cylinder locomotive worked by means of racked rails and toothed wheel. From the design of this steam locomotive Stephenson developed his Killingworth locomotive.

The description and sketch was made by Leighton Dalrymple two weeks after the opening of the Middleton-Leeds railway in 1812. The letter also includes an enthusiastic description and sketch of newly built ‘Cloth Hall’ which revolutionised the weaving industry. The letter is part of a longer incomplete document where the first page appears to be missing.