Negretti & Zambra Mining Borehole Thermometer.
This instrument is what is believed to be a mining borehole thermometer. The glass mercury filled thermometer tube is encased in a cut-away brass tube with a screw top and suspension hanger. The bottom of the brass tube is pierced around the area where the mercury reservoir sits.
Made from brass and glass. Size 11″ x 3/8″ inch.
The back of the glass thermometer tube is etched with the makers name as Negretti & Zambra Ltd. The company went limited in 1948.