Building on the work published in 1995 in the Directory of British Scientific Instrument Makers c. 1550-1851, a database is being created at the Royal Museums at Greenwich based on research into the scientific instrument trades in the second half of the nineteenth and the early twentieth century, up to 1914. The research so far has focused on trade directories and advertisements, with additional material from catalogues and family history and biographical sources. This material is providing a useful resource for tracing some of the links between different manufacturers, such as which firm succeeded another at a particular address, changes in partnerships and company organization, evolution of the kinds of instruments offered for sale, and who was supplying instruments made by someone else. Examples will be given of some of the links which have been traced and an attempt made to examine the light these throw on changes in the industry during the period under review.