About 1850 Robbins & Lawrence took the first of the steps which led to their undoing. The railroad had just been completed through Windsor, and S. F. Belknap, a large railroad contractor, induced them to start in the car business, which, of course, had no rational relation with their main activity of building guns. Mr. Belknap assured them that he could control all the car work in that section, and put in $20,000 as a silent partner. The firm went to a large outlay, but just as they were finishing the first cars, Belknap quarreled with the president of the railroad and the firm could not sell a single car when they had expected to. After a considerable delay they were sold to other roads, and stock which proved valueless was taken in payment. The operation involved an actual loss of $134,000, which was later increased to nearly $240,000. [Illustration: FIGURE 38. ROBBINS & LAWRENCE ARMORY, WINDSOR, VT. FROM AN OLD LITHOGRAPH] In all of their gun work, Robbins & Lawrence used the interchangeable system, and they contributed very largely to its development. Lawrence, Howe, and later Stone, were constantly improving the methods of manufacture. Fitch’s article on Interchangeable Manufacture in the U. S. Census Report of 1880, describes and illustrates a profiling machine built by Howe as early as 1848. The design shown there was used for many years throughout all the gun shops in the country. He also designed a barrel drilling and rifling machine, and he and Lawrence designed and built a plain miller, which was the forerunner of the well-known Lincoln miller. One of these millers, built in 1853, is still running in the shop of the North Brothers Manufacturing Company in Philadelphia. This machine had a rack-and-pinion feed for the table, which chattered badly when starting a heavy cut. The principal improvement which F. A. Pratt introduced in the Lincoln miller was the substitution for this of a screw and nut. The original drawing of this Robbins & Lawrence machine is still on file in the office of the Jones & Lamson Machine Company and shows clearly that it furnished the basis of the design of the Lincoln miller. In 1851 Robbins & Lawrence sent to the Exposition in London a set of rifles built on the interchangeable system, which excited great interest and for which they received a medal. This led to the visit of an English commission which resulted in a large contract to Robbins & Lawrence for Enfield rifles, and for gun machinery which was installed in the Armory at Enfield, near London. It has been said that this contract caused the failure of Robbins & Lawrence. This is not true.