Sentence:  In England about this time the problem of constructing maximum and minimum thermometers was actively taken up. Lord Charles Cavendish first solved this question in 1757, and later in a similar way Magnus, in Berlin, for the <WSD>geothermometer</WSD>, and Walferdin, in Paris, by the "metastatischen" thermometer.” 
Meaning of the word marked with <WSD> tags:  A thermometer designed for measuring extremely high temperatures below ground level.