Jones Josephs conductance bridge
Date: circa 1940
Inventory Number: 1997-1-0373
Classification: Bridge
Subject:
Maker: Leeds & Northrup Company (1903 - 1995)
User: Chemistry Laboratory, Harvard College (founded 1850)
Cultural Region:
Place of Origin:
Dimensions:
17.3 x 59.5 x 59.5 cm (6 13/16 x 23 7/16 x 23 7/16 in.)
With Lid: 24 × 62.5 × 62.5 cm (9 7/16 × 24 5/8 × 24 5/8 in.)
Accessories: lid
DescriptionA large wooden box, square on top and stout on the side. The base, which is beveled, is somewhat damaged near the front left side. Also, the sides have a few small dents and scratches. The lid of the box extends beyond the base on all sides. The lid does not cover, however, two small metal protuberances on opposite ends; the protuberances feature slots into which something external can be plugged in.
Once the lid is removed, the small metal protuberances are revealed to be long, thin arms screwed directly into the box. Removing the lid also reveals the many dials and switches present on the console:
2 safe-style dials near the bottom each allowing the user to choose a setting between 1 and 100;
5 raised black dials in the middle of the console, each encircled by small numbered cylinders, and which each have the labels: '1 OHM,' '1 OHM,' '10 OHMS,' '100 OHMS,' '1000 OHMS';
4 raised dials at other parts along the console, two are brown, the others black;
6 switches, in a row along the top, labeled '10000 OHMS';
14 small cylindrical terminals, in patches along the periphery, some metal and some covered in plastic;
2 rectangular covers, one that reads 'DC,' and the other that reads 'REVERSING SWITCH.'
At least one dial is signed "Velvet Vernier". Overall, the console has a few stains and some of what was previously inscribed by the manufacturer, for example the circuit diagram near the top, has faded.
An orange tag on the instrument is the chemical lab inventory number: "E1209 / C.R.F / G.J."
Once the lid is removed, the small metal protuberances are revealed to be long, thin arms screwed directly into the box. Removing the lid also reveals the many dials and switches present on the console:
2 safe-style dials near the bottom each allowing the user to choose a setting between 1 and 100;
5 raised black dials in the middle of the console, each encircled by small numbered cylinders, and which each have the labels: '1 OHM,' '1 OHM,' '10 OHMS,' '100 OHMS,' '1000 OHMS';
4 raised dials at other parts along the console, two are brown, the others black;
6 switches, in a row along the top, labeled '10000 OHMS';
14 small cylindrical terminals, in patches along the periphery, some metal and some covered in plastic;
2 rectangular covers, one that reads 'DC,' and the other that reads 'REVERSING SWITCH.'
At least one dial is signed "Velvet Vernier". Overall, the console has a few stains and some of what was previously inscribed by the manufacturer, for example the circuit diagram near the top, has faded.
An orange tag on the instrument is the chemical lab inventory number: "E1209 / C.R.F / G.J."
Signedin tiny letters, near the bottom right: LEEDS & NORTHRUP CO.
FunctionThis bridge can be used to determine unknown resistances by balancing two branches of the circuit, one containing a standard resistance and the other an unknown.
Curatorial RemarksInstructions were found with the instrument, which are now in the instrument's file in the CHSI library.
ProvenanceFrom the Department of Chemistry, Harvard University.