601 MEANS OF DETERMINING TIIE QUALITY OF MILK. 
whatever may have been the original density of a given 
sample of the fluid, it is capable of being lowered by the 
fraudulent admixture of warm water, and raised again to 
the former figure by the abstraction of a portion of the 
cream; for the latter will separate rapidly, owing to the 
previous addition of warm water, and thus the double decep¬ 
tion is capable of being carried into effect within a very 
short period after the milk has been first drawn, and will of 
course fail to be detected by the hydrometer. It has, there¬ 
fore, been suggested that the lactometer should always be 
used in combination with the hydrometer, one being supposed 
to serve as a check upon the indications of the other. 
A very ingenious mode of determining the richness of milk 
was devised some years since by M. Donne. The instru¬ 
ment which he employed, called a lactoscope, is constructed 
on a different principle altogether from either of the fore¬ 
going, and professes to enable one to judge of the richness 
of a sample of milk, by measuring the thickness of a film 
of this fluid through which a voluminous body, placed at a cer¬ 
tain distance, can be discovered ; the more dilute the milk, the 
thicker will be the film through which the light will be trans¬ 
mitted, and the measure of the thickness is provided for by 
a scale attached to the instrument. The chief objections to 
the employment of the lactoscope, at least for ordinary every¬ 
day use, would appear to be not only its high price, but the 
difficulty of keeping it in good working order, owing to the 
delicacy of its construction. It requires to be taken asunder 
every time it is used, and if not thoroughly cleansed and 
dried in every part, the screw become clogged and its action 
embarrassed ; in fact, if it gets into careless or unskilful 
hands, it will not fail to become, in a short time, unservice¬ 
able. Lastly, of the microscope. \\ ith the aid of this valu¬ 
able instrument, the number, size, and shape of the oil, or 
cream-particles, can be easily recognised by any one who 
has become expert in its manipulation, and in this way may 
be formed a tolerably fair estimate of the quality of any given 
sample of milk; it must be admitted, however, that few, 
comparatively speaking, have attained to the requisite degree 
of skill and experience to enable them to pronounce at once 
a decisive opinion from the use of this instrument without 
some collateral aid. The expense of a good microscope is 
also a serious impediment to its general adoption as a lac- 
toscopic instrument. It will appear, therefore, from what 
lias been stated in the foregoing remarks, that an instrument 
which, in the hands of ordinary observers, will supply the 
means of determining approximately, or in a rough way, 
