212 MY POULTRY DAY BY DAY 
added occasionally, in order to provide for evaporation. An egg 
preserved by this method can be easily recognised by the roughness 
of the shell. When the egg is boiled the shell will crack, a result 
due to the effect of the lime upon the outer covering, causing it to 
be hard and brittle. Preserved eggs are not recommended for 
boiling, but, if it is desired to use them in this way, the cracking 
may generally be prevented by pricking the broad end with a 
needle when the egg is about to be boiled. 
WaTER-GLASS 
Water-glass is a strong solution of silicate of soda in water vary- 
ing in specific gravity, according to the amount of silicate dis- 
solved. The strongest solution usually found in commerce has a 
specific gravity of 1-7 and contains approximately equal parts by 
weight of sodium silicate and water. A ready means of ascer- 
taining whether the water-glass is uniform in different supplies 
would be to weigh a measured ounce of the water-glass. One 
ounce by measure of the concentrated solution of specific gravity 
1:7 should weigh 1-7: 0z., or nearly 13 0z.; if it weighs less than 
this it contains less silicate, and more of the water-glass should 
therefore be used in making the dilute solution. 
In preparing the water-glass for use, five or ten times its bulk of 
pure boiling water should be added to the concentrated solution 
according to its strength. The preparation should be quite cold 
before it is used. Experiments in America have shown that a 
8 per cent. solution (7.e. 8 parts by measure of the concentrated 
solution to 97 parts of water) yields as good results as that generally 
recommended—namely, 10 per cent. A 5 per cent. solution may 
be used with safety, and with this strength there is less danger of 
giving the eggs an objectionable flavour than with the stronger 
solution. When the water-glass is added to the water the two must 
be very carefully and thoroughly mixed. The eggs may be dipped 
in the water-glass and dried off, leaving a film on the shell, and 
then stored upon shelves, or they may be kept in the liquid until 
sold or used. The latter method is to be preferred. When taken 
