43 
of determining the amounts of copper which are dissolved 
by water charged with carbon dioxide under a pressure of 
several atmospheres : the results are subjoined. 
The apparatus were the same as that employed in the 
experiments with lead. 
Surface of copper exposed = 2100 sq. mm. 
Table G. 
Copper dissolved by water charged with carbon dioxide 
at a pressure of about 6 atmospheres. 
1 
Salt. 
Mgms. 
per 
Litre. 
Grains 
per 
Gallon. 
Mgms.p 
24 hrs. 
lopper c 

er Litre 
48 hrs. 
.issolved 
Grains j 
24 hrs. 
\ 
)er Gall. 
48 hrs. 
Potassium Carbonate ... 
40 
2-8 
ro 
D 2 
07 
•084 
Ammonium Nitrate 
16 
1-12 
0-8 
» • • 
•056 
Ditto 
80 
5-60 
i -2 
1-4 
•084 
•098 
Distilled Water 
... 
... 
0-4 
0-6 
•028 
•042 
Distilled water, charged with carbon dioxide, under a 
pressure of (approximately) 6 atmospheres, dissolves about 
three times as much copper as the same water charged at 
the ordinary atmospheric pressure. Nitrates increase this 
action and carbonates diminish it. 
III. Influence of house cisterns upon the water supply. 
There appears to be a somewhat wide-spread feeling 
against the use of cisterns in dwelling-houses, which is, I 
suppose, chiefly due to the fact that the waste pipe from 
the cistern is generally in connection with the soil pipe 
which carries off the drainage of the house. 
The hurtful sewer gases may thus readily find their way 
into the cistern, and so contaminate the water therein 
stored. On the other hand, however, it may be urged that 
inasmuch as the water in cisterns is frequently changed 
there is no great probability that the water actually used 
for domestic purposes will be, at any rate largely, con- 
taminated by sewer gas. I have attempted to obtain 
some definite measurements of the amount of contamination 
