These were used for keeping hot water to replenish the teapot
Silver Tea Urns, also known as samovars, They were not usually found before about 1765 and the early ones were heated with charcoal. About 20 years later more sophisticated designs were produced after the introduction of a pre heated iron rod which could be placed into the tea urn within a central tube. By the year 1800 the use of spirit lamps underneath the urn became popular. Smaller urns were also made for coffee and these normally didn’t have a heating device.
Silver Tea Kettles date from Queen Anne times. These were made until the 1770's when the tea urn took over the job of providing hot water. Although kettles were still made between 1770 and 1840 they were less common until Victorian times when they were reintroduced, probably because of the discovery of odourless spirit for the burners