On a New Method of Testing Milk. 
585 
on this inner small tube are marked black lines, which become 
invisible when milk is poured into the instrument, and only a 
little water is added to it, but which are clearly seen when more 
water is gradually added to the milk. The richer the milk is in 
cream-globules, or, in other words, 
in butter-fat, the more water must 
be added to it before the black lines 
on the inner tube of Feser's lacto- 
scope become visible in the watered 
Feser's Lactoscope (one-half 
the natural size). 
milk surrounding the inner tube 
and, on the other hand, if the milk 
is poor in cream or watered, less 
water is needed to show the black 
lines on the inner cylindrical tube. 
All that is required in testing 
milk by this instrument is to deliver 
by means of a pipette, B, a measured 
quantity of milk (4 cubic centi- 
metres), or, in other words, to suck 
into the pipette milk up to the 
mark in the narrow tube end of the 
pipette, and to let it flow into Feser's 
lactoscope, and to blow out the last 
drop from the pipette. Common 
pump-water is then gradually added 
to the milk, the contents of the 
lactoscope are shaken up, to secure 
perfect mixture, and the addition of 
water is stopped as soon as the 
black lines on the inner cylindrical 
tube become plainly visible. The 
figures on the right side of Feser's 
lactoscope then show at once the 
percentage of pure butter-fat in the 
milk, whilst the numbers on the liliHiiillA 
left-hand side merely show the 
quantity of water, in cubic centi- 
metres, that has been added to bring 
out the black lines : these numbers 
might as well be omitted, as they 
may lead only to confusion, and are not wanted. The whole 
operation of testing milk by this method occupies only a few 
minutes' time, and nothing can be more simple and easy in 
practice. 
This instrument, I am informed, is employed extensively in 
Germany, Holland, and Denmark, by dairymen, milk con- 
tractors, and officers appointed by the authorities to test the 
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