Aug. 1, 1894.] Supplement to the " Tropical Agriculturist." 
145 
The following is the average composition of 
genuine cakes and meals in common use : — 
Albumi- 
Carbo- 
noid. 
Oil. 
hydrates. 
Linseed .... 
21 
37 
20 
Linseed cake . . 
29 
11 
32 
Rape cake 
31 
10 
30 
Poppy cake . . 
35 
10 
22 
Hemp cake . . 
30 
8| 
17 
Sunflower cake 
33 
9 
27 
Cotton cake . . 
28 
7| 
30 
„ (decorticated) 
44 
15" 
20 
Gingelly cake 
. 37 
13 
21 
Rice meal 
11 
10 
50 
Rye meal 
. 14A 
H 
60 
Palm kernel cake 
. 17" 
10 
41 
Palm kernel meal . 
. 19 
3^ 
44 
Earth-nut cake 
(shelled) 
! 47 
7i 
25 
Locust bean meal 
2 
74 
Dried grains . . 
. 20 
8 
50 
Bran 
. 13a 
3i 
56 
THE LACTOMETER IN ITS TRUE LIGHT. 
The lactometer, or lactodensimeter, as it has 
been called, to distinguish it from another simple 
instrument, the creamometer, was at one time 
a great favourite. In France, a few years ago, 
if not indeed now, the Police would take action 
at once on a reading of that instrument, and 
turn milk out into the gutter if it were con- 
demned. And in London, the lactometer is ex- 
posed for sale in shop windows, and both the 
public and milk dealers trust to it. Even in. 
some recent manuals intended for the guidance 
of medical officers of health, the use of the 
lactometer is recommended. In one of them in 
particular — Dr. Edward Smith's — which claims 
a sort of pseudo-government sanction, the lacto- 
meter is very prominently put forward, and 
commended as being for milk what the hydro- 
meter is for alcoholic fluids. 
But, although it is so very popular, and al- 
though it has been so implicity trusted, the 
lactometer is a most untrustworthy instrument. 
There hardly ever was an instrument which has 
so utterly failed as the lactometer. It confounds 
together milk which is exceptionally rich, with 
milk which has been largely watered ; and many 
a poor French peasant, bringing the best and 
unadulterated produce of his dairy into a French 
town, has been ruthlessly stopped by the Police, 
who have dipped their lactometer into the milk, 
and forthwith sent it down the gutter as if it 
had been milk and water. 
Very curious things, too, are done in this 
country by reason of trust in the lactometer. 
There is a prison not far from London, and the 
prison authorities are specially particular about 
their supply of milk. They allow no milk to 
enter the prison unless it comes up to the M. 
mark on a certain lactometer. The M. mark is 
pitched very high, and the milk purveyor readies 
the M. mark by skimming the milk. 
A very little consideration will suffice to make 
intelligible the obliquity of the indications of 
the. lactometer, and to show how untrustworthy 
it must be. The lactometer, as, of course, will 
bu understood, is simply the hydrometer applied 
to milk ; and readings of the instrument are 
neither more nor less than specific gravities. 
The more milk-sugar and caseine and mineral 
matter there is in a given specimen of milk, 
the greater (other things being equal) will be 
its density or specific gravity, and the higher 
the lactometer reading. 
If, however, fat globules (as happens in the 
instance of milk) be diffused through the fluid, 
then, because fat is lighter than water, the effect 
of the other milk-solids on the gravity of the 
liquid will be more or less neutralized. The 
density of milk-fat is about 09 water being 1-0. 
Now, if a solution of caseine aud milk-sugar, 
of specific gravity 1-030, be sufficiently charged 
with fat globules, its specific gravity may be 
sent down even below the gravity of water. How 
much would be required to bring about such a 
result is a matter of simple calculation. 
This being understood, it will be obvious that 
if the specimens of milk differ in specific gravity, 
there must be two distinct and equally valid 
ways of accounting for the difference. The milk 
with the lower gravity may be milk let down 
with water, or let down with fat, i.e., milk let 
down by being enriched. 
By way of example, I would just refer to 
the specific gravity of the so-called striplings, 
which are the last portions of milk wrung out 
of the udder at the termination of the milking. 
These are richer in cream than the average mass 
of the milk, and they have a much lower density 
than average milk. 
I have myself examined strippings with a 
specific gravity of T020, and a specific gravity of 
1-025 is by no means uncommon. In the instance 
of stippiugs of the latter gravity, I found the 
percentage of solids to be 18-74. 
Now, if all we knew concerning a sample of 
milk was that its gravity was 1025, we might 
with equal reasonableness conclude, either that it 
contained fifteen or twenty per cent, of extraneous 
water, or that it was surcharged with cream. 
If, by adding fat to milk, the specific gravity is 
lowered, it follows that by substracting fat (i.e., 
by skimming) the s pecilic gravity is raised ; and 
hence the explanation of the reaching of the 
high M. mark by skimming. 
A certain trick of the milk trade ia fostered 
by the employment of the lactometer. The milk 
is partially denuded of cream (accomplished 
conveniently by adding a certain quantity of 
skimmed milk to the fresh milk), and thereby 
raised in gravity. That being accomplished, it 
is dosed with water, and its gravity is thereby 
lowered to the normal standard. 
Let no one think that he would discover such a 
trick by making an estimation of cream ; for 
watered milk throws up its fat in the form of 
cream more perfectly than unwatered milk. 
Another objection relative to the lactometer 
(which, however, pertains to the application of 
the hydrometer to organic fluids generally) is 
drawn from the circumstance that a comparatively 
small change in density corresponds to a great 
change in composition. Making tuial abstraction 
of the difficulty and uncertainty dependent on 
the cream, and regarding milk as a solution of 
caseine and milk-sugar, it will be seen that whore- 
as the specific gravity of water rises only from 
I '000 to 1-032 in passing into milk, the water 
