By a further study from the Ontario data of the relation of the evaporation to the results in livable chicks, it can be readily observed that all good hatches have evaporation centering around the 12 per cent. moisture loss, and that all lots with evaporations above 15 per cent. hatch out extremely poor.

The general averages of the machines supplied with some form of moisture was 35 per cent. of all eggs set, in chicks alive at four weeks of age, while the machines ran dry gave only 20 per cent. of live chicks at a similar period.

Now, I wish to call attention to a further point in connection with evaporation.  If the final measure of the loss of weight by evaporation were the only criterion of correct conditions of moisture in the chick’s body, the hatches that show 12 per cent., or whatever the correct amount of evaporation may be, should be decidedly superior to those on either side.  That they are better, has already been shown.  But they are far from what they should be.  An explanation is not hard to find.  The correct content of moisture is not the only essential to the chick’s well being at the moments of hatching, but during the whole period of incubation.  Under our present system of incubation, the chick is immediately subject to the changing evaporation of American weather conditions.  The data for that fact, picked at random, will be of interest.  The following table gives the vapor pressure at Buffalo, N. Y., for twenty consecutive days in April: 

April 1..................170
2..................130
3...................95
4..................103
5..................110
6..................106
7..................154
8..................183
9..................245
10.................311
11.................342
12.................286
13.................219
14.................248
15.................217
16.................193
17.................241
18.................306
19.................261
20.................204

Supposing a hatch to be started at the beginning of the above period, by the end of the first week, with the excessive evaporation, due to a low vapor pressure, the eggs would all be several per cent. below the normal water content; the fact that the next week was warm and rainy, and the vapor pressure rose until the loss was entirely counterbalanced, would not repair the injury, even though the eggs showed at the end of incubation exactly the correct amount of shrinkage.  A man might thirst in the desert for a week, then, coming to a hole of water fall in and drown, but we would hardly accept the report of a normal water content found at the post-mortem examination as evidence that his death was not connected with the moisture problem.