experimental geology, devising an elaborate series of chemical 

 experiments in order to ascertain the composition of different 

 rocks, and whether one variety could by fusion be transmuted 

 into another. 



Having been initiated by Monget, the explorer of the South 

 Seas, into the art of using the blowpipe, de Saussure employed it 

 extensively in mineralogy. He invented a method of soldering 

 fragments of rock to small glass tubes for the purpose of sub- 

 mitting them to intense heat and decomposing their constituents. 

 He thus ascertained the fusibility of one hundred and thirty 

 minerals, and divided them into six classes, forming a scale of 

 fusibility. His results were published in a treatise, Sur Vusage 

 du Chalumeau. 



De Saussure was not content with determining heights. He 

 was very active in taking observations of the temperatures and 

 depths of ten of the Swiss lakes, and on two occasions (in 1780 and 

 1787) proceeded to do the same in the sea deeps off the Mediter- 

 ranean coast. For this purpose he devised a special form of 

 thermometer capable of resisting the pressure at great depths, 

 constructed on a principle which is still in use. 1 



During the last five years of his life de Saussure made several 

 attempts to determine the temperature of the earth at different 

 depths, a matter which has since his time been made the subject 

 of more detailed observations. 



Much interested by the efforts of Montgolfier at Lyons for the 

 raising of balloons by means of heated air, he made experiments 

 on his own account. He ventured a prophecy, the fulfilment of 

 which seems close at hand, that aeronautics would one day play a 

 part in mountain exploration. He introduced, not without con- 

 siderable opposition, the use of lightning conductors at Geneva and 

 in Italy ; he also invented a self-adjusting windmill, with vanes 

 that opened or closed according to the strength of the wind, the 

 construction of which, according to the Report of a Committee of 

 the Genevese Society of Arts, 'involved difficult and curious 

 physico-mathematical problems.' 



The desire to collect flowers for his invalid mother, the object 

 of de Saussure 's boyish rambles, had been the origin of his earliest 

 vocation, botany. Under Haller's influence, it developed into a 

 1 See Dr. Mill's Note. 



