ADULTERATION OF MILK-LACTOSCOPE. 
milk lie proposes to sell, to stand until the richer portion forms 
a creamy stratum at its surface, then skims off this stratum 
which he sells at a high price, as cream. The remainder and 
impoverished portion of the milk is then undoubtedly heavier 
than before it was deprived of the cream, and its poverty would 
be detected by Quevenne’s hydrometer : but the crafty milkman, 
aware of this, has the adroitness, not only to correct the too great 
weight of the fluid, but to do so to his own increased profit. He 
knows that the addition of water will diminish the specific 
gravity of his skimmed milk, and he accordingly mixes with it 
just so much of that cheap liquid as will reduce its weight to that 
of milk of the proper richness. 
96. This manoeuvre is attended also with another deceptive 
effect; it is found that the mixture of water with milk facilitates 
the disengagement of cream, and expedites its collection at the 
surface. Whatever creamy particles, therefore, may remain in 
the milk thus impoverished and adulterated, will rise quickly to 
the surface, and collecting there, will deceive the consumer, pro¬ 
ducing the impression that the milk on which cream so quickly 
collects, must necessarily be rich. 
The great importance of discovering such an easy and practi¬ 
cable test of the quality of an element so important to the 
sanitary condition of the people, as milk, ought, one should have 
supposed, to stimulate scientific men to such an invention. The 
frauds practised so extensively by the vendors of milk on great 
public establishments, such as hospitals and schools, are notorious. 
An eminent medical practitioner says, that in conversing with one 
of the great milk contractors of the public establishments in 
Paris, during a season in which forage had risen to a very high 
price, the milkman observed frankly, and with a smile, “in 
common seasons, we do put a little water to the milk, but at pre¬ 
sent we are obliged to put milk to the water.” 
97. Dr. Donne has invented an instrument to ascertain the 
richness of milk, which he calls a lactoscope, which was presented 
to the Academy of Sciences, and favourably reported upon by a 
committee consisting of MM. Thenard, Chevreul, Boussingault, 
Regnault et Seguier, who experimented with it and verified its 
results. This instrument is based upon the fact, that while the 
butter globules, which float in milk, are opaque, the liquid which 
surrounds them is nearly transparent. It follows from this, that 
the transparency of milk will diminish as its richness increases, 
and vice versa . 
The lactoscope consists of two plates of glass, set parallel to 
each other, so as to form a cell in the end of a tube, like an 
opera-glass, the cell being at the wide end of the tube. A screw- 
ICd 
