108 Scientific Proceedings, Royal Dublin Society. 
quantity only with the air of the atmosphere. To this particular 
species I gave the name of fixed air.”” 
The elder De Saussure? employed diluted lime water as a test 
for carbonic anhydride on the summit of Mont Blane and the. 
Col du Géant, and also detected the gas by a second method, viz. 
by means of strips of paper moistened with caustic potash solution, 
which after exposure to the air for about an hour and a half 
became dry and then gave a brisk effervescence with acids. He 
further states that he repeated the experiment with lime water on 
the seashore (the lake of Geneva ?), and found that in the same 
time a thicker deposit of chalk was produced. 
“<The first chemists who have left us instructions concerning 
the investigation of atmospheric carbonic acid admit that free air, 
when washed with alkaline solutions in a eudiometric tube suffers 
a diminution in volume, which indicates, according to circum- 
stances, one or two hundredths of carbonic acid; for, as they inform 
us, its proportion, as well as that of the oxygen, vary in different 
places.” 
The younger De Saussure? (Théodore), to whom the above 
statement is due, mentions the names of Fourcroy* and Humboldt® 
as the first chemists who sought to determine atmospheric carbonic 
anhydride. According to Blochmann,’ Humboldt’ initiated this 
1 Thorpe (Chem. Soc. Journ., 5 [1867], p. 189) attributes Black’s discovery to 
M‘Bride of Dublin, in 1764, and the same statement has been made by others 
(Symons and Stephens, idid. 69 [1896], p. $69); but this is incorrect, for Black tells 
us (Lectures, vol. ii., p. 88), ‘‘Some time after I had made and published, in my 
inaugural dissertation, the experiment you have seen, the attention of some other 
persons was excited, and keenly engaged with this new aud interesting subject. The 
late Dr. M‘Bride of Dublin began to attend to it, in consequence of some letters which 
I wrote to my friend Dr. Hutcheson, then lecturer on chemistry in Trinity College.” 
Moreover, M‘Bride himself (‘‘ Experimental Essays,’’ p. 178) distinctly gives the 
credit of the discovery to Black, and does not appear to have made any experiments of 
his own to prove the presence of carbonic anhydride in air. He merely made use of 
lime-water as a test for that substance in the gases evolved from putrefying vegetable 
and animal matters. 
* Horace Bénédict De Saussure, ‘*‘ Voyages dans les Alpes,” 4 [1796], par. 2010. 
3 Théodore De Saussure, ‘“‘ Annales de Chimie et de Phys.,’’ 44 [1830], p. 5. 
# Fourcroy, ‘‘ Syst. des Conn. Chim.,’’ vol. i. [1801], p. 158. 
6 Humboldt, ‘Journ. de Phys.,’’ 47 [1798], p. 202; ‘‘Gilbert’s Annalen,”? 
8 [1800], p. 77. 
6 Blochmann, “ Liebig’s Annalen,’’ 237 [1887], p. 39. 
7 A. y. Humboldt, “Versuche iiber die chemische Zerlegung des Luftkreises,’’ 
Brunswick, 1797. 
