142 The Hen at Work 



embryo either dies or becomes so weakened that it 

 fails to break the shell. 



Other much more extended and more careful 

 experiments have been made which show that 

 turning the eggs has -a vital effect on the number 

 hatched. If we turn them five times during the 

 twenty-four hours, five or six per cent, more chick- 

 ens may be expected than if we turn only twice. 

 It is, however, no small task to turn eggs five 

 times, at intervals of about five hoiu-s, during day 

 and night, and as the return is a small number of 

 chicks, which are probably not the strongest in the 

 lot, most of us will be content with turning twice 

 each day, unless the eggs are of vmusual value or 

 interest. 



Testing. — ^At about the sixth day it is time to 

 test each egg to see if it has a growing embryo 

 within. There are several devices for testing eggs. 

 When many are to be examined a box is arranged 

 to hold a lamp or electric light. The eggs are then 

 placed against a hole in the box. If the room is 

 dark the light from within the box will penetrate 

 the egg-shell and show much of what is going on. 



Where there are not many eggs to be handled a 

 very simple and practical tester is provided by 



