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ANNALS NEW YORK ACADEMY OF SCIENCES 
Exp. 1. The residue weighed 0.0378 gramme 
Exp. 2. “ “ “ 0.0367 
Average 0.0372 “ 
Hence one liter of water acting for sixteen days on 500 grammes of this 
broken trap would dissolve 0.1860 gramme of its constituent material. 
The above residues were chiefly white, and dissolved almost entirely in 
hydrochloric acid, with slight effervescence. A small quantity of a brown¬ 
ish material, apparently organic matter, remained. With the spectroscope, 
the solution gave lines of sodium and calcium. 
In the residue No. 2 above silica and alumina were determined as follows: 
Si0 2 
Al 2 0 3 + 5 Fe 2 0 3 
0.0052 gramme 
0.0023 
Hence one liter of water acting for sixteen days on 500 grammes of the above 
broken trap would dissolve 0.0260 gramme of silica and 0.0115 gramme of 
alumina. 
The greenish flocculent matter collected on the filter was dried, ignited 
and weighed, as follows: 
Experiment 1, 0.0514 gramme 
Experiment 2, 0.0936 “ 
Hence one liter of water acting for sixteen days on 500 grammes of the 
above trap would remove 
Experiment 1, 0.2570 gramme 
Experiment 2, 0.4680 “ 
This substance before ignition resembled diabantite. After ignition, 
it had a ferruginous orange color. A small quantity of the natural soft 
coating was taken from one side of a crevice in a specimen of trap, and after 
ignition it had a similar color. 
Trap rock being thus soluble in pure water, it would probably be still 
more soluble in meteoric water which had absorbed carbonic acid, oxygen, 
organic acids or other such substances before reaching it. Rain becomes 
charged with gases acquired from the air in falling, taking up from 3 to 30 cc. 
per liter. The oxygen is found in larger proportion than in air, being some¬ 
times as much as 38% of the dissolved gases. It also contains about 3% of 
carbonic acid anjd traces of carbonate and nitrate of ammonia and free nitric 
acid, besides small solid particles of dust, salts and organic matter. 1 In 
1 V. B. Lewes': Service Chemistry, p. 102, London, 1895. 
