THE MICROSCOPE. 21 
A few months since it was discovered that some manufac- 
turers were not only using in their lower grades of mustard ex- 
cessive quantities of flour, but were replacing the flour in part 
with terra alba, and were substituting for the tumerica coal-tar 
color—Martius’ yellow, scientifically termed “calcium dinitro- 
naphthalate.” This color, besides being as explosive as gun- 
powder when unmixed with anything else, was proved by ex- 
periments on dogs to be poisonous. 
That copper compounds have frequently been used to give 
a bright green tint to pickles and preserved green vegetables 
generally has long been known. It may perhaps not be known 
that minute quantities of copper have been found in almost all 
vegetable products, apparently as an accidental constituent, 
since the amount varies according to the soil upon which the 
cereals, potatoes, etc., have been grown, and the element is en- 
tirely absent. In an experiment connected with this investiga- 
tion, copper to the extent of 2.57 parts of the metal per million 
was found in fresh cucumbers bought in the market. In some 
molluses, and in the coloring matter of the feathers of certain 
tropical birds, copper is an essential constituent; it has fre- 
quently been detected in the human body. 
The question as to whether copper compounds are really 
poisonous has been vigorously disputed, and cannot be regarded 
as positively settled. It seems probable that to certain persons, 
possibly the larger portion of mankind, they are poisonous, 
while to others they are not. 
The westerner who visits this city on business or pleasure 
may “forget to taste ” the Croton water; but how would he feel 
if he were told that the sparkling effervescent water which he 
drank with his claret at some fashionable club, even though it 
bore some well-known foreign brand with the label and cork- 
fastening looking as though the bottle had just come from abroad, 
was drawn from a well sunk on Manhatten Island, and was con- 
taminated with the drainage of some of its busy streets and 
leaky sewers. Yet that has been often the fact. 
It must not be rashly inferred from the items which from 
time to time are published that everything which we purchase 
in the way of food and drink is bad or adulterated. Probably 
if the proportion of adulterated articles to the whole number 
