The Primus stove was the first pressurized-burner kerosene (paraffin) stove, developed in 1892 by Frans Wilhelm Lindqvist, a factory mechanic in Stockholm. The stove was based on the design of the hand-held blowtorch; Lindqvist’s patent covered the burner, which was turned upward on the stove instead of outward as on the blowtorch. The same year, Lindqvist partnered with and established J.V. Svenson’s Kerosene Stove Factory for manufacturing the new stoves which were sold under the name Primus. The first model was the No.1 stove, which was quickly followed by a number of similarly-designed stoves of different models and sizes. Shortly thereafter, B.A. Hjorth & Co. (later Bahco), a tool and engineering firm begun in Stockholm in 1889, acquired the exclusive rights to sell the Primus stove. The efficient Primus stove quickly earned a reputation as a reliable and durable stove in everyday use, and it performed especially well under adverse conditions: it was the stove of choice for Fridtjof Nansen's North Pole attempt, Roald Amundsen's South Pole expedition, and Richard Byrd’s North Pole expedition. Primus stoves also accompanied George Mallory's ill-fated expedition to Mount Everest in 1924, as well as Tenzing and Hillary's successful one in 1953. While many other companies also made portable stoves of a similar design to the Primus, this style is often generically referred to as a "Primus" stove, regardless of the manufacturer. Construction The Primus No. 1 stove, made of brass, consists of a fuel tank at the base, above which is a "rising tube" and the burner assembly. A steel top ring on which to set a pot is held above the burner by three support legs. Other Primus-style stoves may be larger or smaller, but have the same basic design. The No. 1 stove weighs about , and measures about high with an overall diameter of just under . The tank, about high, holds a little over of kerosene and will burn for about four hours on a full tank. Principle of operation To light the stove, the user pours a small amount of alcohol into a circular "spirit cup" just below the burner and lights it to heat the burner assembly. When it is hot, the user pressurizes the tank by means of a small hand pump integrated into the housing, which forces kerosene from the tank up through the rising tube (A) and the ascending pipe (B) to the pre-heated burner