New York — Joseph Gatty (fl. 1794); barometers, thermometers and phil- 



Continued osophical instruments. 



James Ham (fl. 1754-1764); mathematical instruments. 

 William Hinton (fl. 1772); mathematical instruments. 

 A. Lamb & Son (fl. late 18th century); mathematical instru- 

 ments. 

 Anthony Lamb (1703-1784); mathematical instruments. 

 John Lamb (1735-1800); mathematical instruments. 

 M. Morris (fl. 1785); protractors. 



Widow Balthaser Sommer (fl. 1753); optical instruments. 

 Charles Walpole (fl. 1746); mathematical instruments. 

 James Youle (1740-1786); surgical instruments. 

 John Youle (fl. 1786); surgical instruments. 



OHIO 



Columbus: Augustus Piatt (1793-1886); mathematical instruments. 



Benjamin Piatt (1757-1833); surveying instruments and clocks. 

 Gallipolis: Joseph (fl. 1792) and Francois Devacht; watches, compasses, 



and sundials. 



PENNSYLVANIA 



Bucks County: W. L. Potts (late 18th century); surveying instruments. 



George Wall, Jr. (fl. 1788); surveying instruments. 

 Germantown: Christopher Sower (c. 1724-1 740); mathematical instruments 

 and clocks. 

 Christopher Witt (fl. 1710-1765); mathematical instruments 

 and clocks. 

 Harrisburg: Frederick A. Heisely (1759-1839); clocks and mathematical 



instruments. 

 George Heisely (1789-1880); clocks and mathematical instru- 

 ments. 

 Lancaster: George Ford (late 18th century to 1842); surveying and nautical 



instruments. 

 George Ford II (fl. 1842); surveying and nautical instruments. 

 Frederick A. Heisely (1759-1839); clocks and mathematical 



instruments. 

 George Hoff (1740-1816); clocks, surveying instruments. 

 Thomas Mendenhall (fl. 1775); mathematical instruments and 

 clocks. 

 Norristown: David Rittenhouse (1732-1796), practitioner; astronomical and 



surveying instruments. 

 Philadelphia: Owen Biddle (1737-1799), practitioner. 



Thomas Biggs (fl. 1792-1795); surveying instruments. 

 Isaac Brokaw (fl. 1771). 



Benjamin Condy (fl. 1756, d. 1798); mathematical instruments 

 and sand glasses. 



163 



