Rare Negretti & Zambra rail expansion thermometer for 45 and 60 foot rails

Dating to the 1930's, this unusual instrument by Negretti & Zambra is designed to gap train rails allowing for expansion according to ambient temperature during installation. Comprising of a fahrenheit thermometer encased in a copper block, it's a highly conductive device which measures expansion from 1/8 to 5/8 inches. This particular example is quite rare as it has a dual scale for both 45 and 60 foot rail lengths, indicating it was made after 1929 when 60 foot rails were introduced, but still having to facilitate transition from the previous 45 foot standard. Housed in an oak box measuring 6"x2"x1 it weighs just over 300 grams and in very good condition with the thermometer in good working order and no gaps in the line.

Please study the photos as they are part of the description, and I will be happy to answer any questions if I can. Please check out my other auctions for more interesting items.

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