Original indenture of agreement for erection of a rotative engine

Original indenture of agreement for erection of a rotative engine, dated March 1st 1786, between James Watt and Matthew Boulton of the one part and Samuel D. Liptrap of the other, framed and glazed in Museum

This indenture of agreement, made March 1st, 1786, between James Watt and Matthew Boulton of the one part and Samuel D. Liptrap and partners of the other, is for the erection and maintenance by the latter of a double-acting rotative beam engine at a distillery near Whitechapel Road (i.e., where Durward Street now stands), and for the payment to the former of an annual premium during the unexpired term (i.e., of 14 years) of Watt's patent. The engine was to be of 10 h.p., having a cylinder 17 in. diam. by 5 ft. stroke, to be used for grinding malt or other grain and for pumping liquids in the distillery The very important step of adapting the engine to produce rotative motion in order that it might enter the wide field of industrial employment was made by Watt in 1781-84. Forestalled in the use of the crank, he schemed several equivalent mechanisms (see No. 174-8); he made the engine double-acting and invented the parallel motion to take the place of the flexible connection between the piston rod and the beam. Boulton and Watt sold their pumping engines on a royalty of one-third of the saving in coal resulting as compared with an atmospheric engine doing the same work, and on the introduction of their rotative engine adopted a premium similarly based on the saving resulting as compared with the power (e.g., of horses) which was replaced.