414 Royal Society. 



which was however effectually prevented by the guides, who, alarmed 

 at the idea of a longer stay amidst those icy heights, destroyed all 

 the remaining provisions, necessarily compelling the De Saussures 

 to descend to Cormayeur. 



From this period we find Theodore De Saussure always accom- 

 panying his father, who was not slow in availing himself of the great 

 advantages derivable from his son's labours. In 1789, they made 

 the very difficult tour of Monte Rosa, it being the first time that 

 the gold mines of Macugnaga were visited by men of science. It 

 was during this excursion that young De Saussure restored by experi- 

 ments that confidence in the accuracy of the barometer for measu- 

 ring heights, which the assertion of Bouguerhad tended to weaken. 

 He made seventy experiments at different heights, and in calculating 

 the results, was always careful to make the necessary corrections 

 for temperature and humidity, which Bouguer appears to have neg- 

 lected. The enthusiasm and physical energy of young De Saussure 

 were almost too great for his father, who was now aged, and weak- 

 ened by various illnesses, and consequently we often find the latter 

 compelled to resist his son's desire to prolong their arduous excur- 

 sions. 



The storms of the Revolution, more powerful than those of the 

 Alps, at length put an effectual stop to these useful scientific excur- 

 sions, which had been continued for so many years. Theodore de 

 Saussure, in common with many men of his age, was compelled to 

 leave his country. He visited this country with Alexander Marcet, 

 who many years afterwards became his colleague in the Academy at 

 Geneva. After travelling over England and Scotland, he returned 

 to Geneva, and resolved henceforth to devote his life to scientific 

 pursuits. The taste which he had acquired for chemistry under his 

 father's tuition, had been strengthened in England and in France, 

 where that science was eagerly cultivated; and on his return to 

 Geneva, he determined to select the vegetable kingdom for the field 

 of his researches, and zealously applied himself to discover by ex- 

 periments the influence of the atmosphere and of soils upon plants, 

 and the various chemical changes which they undergo. With the 

 exception of some few accessory labours, M. de Saussure spent a 

 long life upon this branch of science ; and it may be truly said that 

 he has done more to advance the knowledge of vegetable physio- 

 logy than any other person. It is worthy of remark that he laboured 

 seven years silently, before publishing the results of his investiga- 

 tions. These were comprised in his work entitled "Recherches 

 Chimiques sur la Vegetation," which appeared in 1804. He sub- 

 sequently published in the Annales de Physique et de Chimie, the 

 results of his investigations into the action of the petals of flowers 

 upon the atmosphere. The great importance which he attached 

 to the nutritive power of carbonic acid upon plants, directed his 

 attention to the proportion of this gas in the atmosphere. In 1816, 

 he published, in the first volume of the Bibliotheque Universelle, 

 some researches on this subject, which being greatly extended, 

 formed afterwards a paper which was published in 1830 in the 



