Between 1791 and 1795 the same address was also occupied by a cooper named Michael Davenport, and from 1797 to 1801 by "the Widow Davenport," presumably widow of Michael. From 1802 to 1804 the same address is listed for William Davenport, "Mathematical Instrument Maker," apprentice to William Dean, and believed to be the son of Michael. During the next ten years Davenport's address was 45 South Front Street, and then, to 1820, was 25 South Front Street.[64] Several brass surveying compasses bearing his name have survived. Another maker of mathematical instruments about whom nothing further is known is Charles Taws, who was listed in this manner in the Philadelphia directory of 1795. [Illustration: Figure 30.--Brass surveying compass marked "F. Heisely Fred:*town." In collection of Ohio Historical Society, Ohio State Museum.] The making of instruments in glass appears to have been a specialized business in the Colonies, because those who worked in this field do not appear to have produced instruments in other materials. One of these makers of glass instruments--specifically barometers, thermometers and "Glass Bubbles to prove spirits, of different kinds"--was Alloysius Ketterer. He maintained a shop in the house of a Charles Kugler at "the sign of the Seven Stars," corner of Race and Fourth Streets in Philadelphia, in 1789. He moved to another address in Race Street in 1790 and was eventually succeeded in business by Martin Fisher, who increased the number of types of glass instruments made and sold at the shop.[65] Henry Voight (1738-1814) was a man with a varied career. Of German ancestry, he was trained as a clock-and watchmaker, and he was a skilled mechanic. He operated a wire mill in Reading, Pennsylvania, in 1780 and moved shortly thereafter to Philadelphia, where he established a clockmaker's shop on Second Street. He became a close friend of the inventor John Fitch in about 1786, and in the following year he became a shareholder in Fitch's company for producing steamboats. In 1792 he entered into a short-lived partnership with Fitch to manufacture steam engines. In 1793 he invented a process for making steel from bar iron. In the same year President Washington appointed Voight to the position of chief coiner of the Philadelphia Mint, and he continued in that position until his death in 1814. He was closely associated with David Rittenhouse, Andrew Ellicott, Edward Duffield, and others. Although there is no record of Voight's career as an instrument maker, there is nevertheless some evidence that he worked in that field. In the collection of the U.S. National Museum there is a brass equal-altitude telescope (fig. 31) made about 1790, that is signed "Henry Voigt." His name was spelled "Voigt" and "Voight" interchangeably.