RARE 19th Century Lord Kelvin (Sir William Thomson) Vertical Force Magnetometer

Up for auction is a highly collectible and historically significant Lord Kelvin Vertical Force Magnetometer, manufactured in Glasgow by Kelvin's preferred instrument maker, James White. This scientific instrument was designed to measure variations in the vertical component of the Earth's magnetic field - a critical tool for the late 19th-century terrestrial magnetic surveys and maritime compass calibration. Because the firm changed its name to Kelvin & James White Ltd. in 1900, the "J. White" signature on this unit securely places its manufacture in the late Victorian era.

The instrument features deep, crisp historical engravings: "SIR WM THOMSON'S VERTICAL FORCE INSTRUMENT No. 115 J. WHITE GLASGOW". The original black patinated brass finish is present with normal surface scuffs and light wear from field use. The top glass viewing port is clear and intact with zero cracks. The brass screws are original.

The instrument comes in its original matching mahogany transit box featuring its vibrant blue protective felt lining. The bottom of the inner wood compartment features a clear hand-scrawled matching pencil inventory mark "115", proving the box and instrument have lived together for over a century.

Tucked inside the box is a fascinating handwritten graphite ledger slip detailing local field calculations, dates and locations, adding historical context.

This delicate scientific antique will be securely packed with ample bubble wrap to ensure safe transit. Fully insured shipping.