INCUBATION 
Buffalo, St. Louls, San Fran- Cario, 
5 
Month N. Mo. cisco. Egypt 
January ........5. 87 98 311 279 
February .......... 81 94 310 288 
March ..........-- 138 224 337 287 
APPL 05.5 ie tied es 171 283 332 311 
MIA iste dates eines 3% 301 423 317 328 
JUDO worded Os Rew w ie 466 550 345 365 
JULY ss csewesaeeses 546 599 374 413 
August .........005 496 627 382 435 
September ........ 429 506 389 372 
October ........648. 285 327 342 365 
November ......... 271 225 285 321 
December.. ....... 143 183 243 397 
A study of the extent of daily variations is also of interest. 
As a general thing they are less extreme in localities when 
the seasonal variations are also less. In Cario, however, which 
has a seasonal variation greater than San Francisco, the daily 
variations during the hatching season are much less than in 
California. This is due to a constant wind from sea to land, 
and an absolute absence of rainfall, conditions for which 
Egypt is noted. 
Nearness to a coast does not mean uniform vapor pressure, 
for with wind alternating from sea to land, it means just the 
opposite. 
As will be readily seen the months in spring which give 
the best hatches, occupy a medium place in the humidity scale. 
The fact that both hens and machines succeed best in this 
period, is to me very suggestive of the possibility that with an 
incubator absolutely controlling evaporation, much of the sea- 
sonal variation in the hatchability would disappear. 
The uniform humidity of the California coast is shown in 
the above table. This is not inconsistent with the excellent 
results obtained at Petaluma. 
The Egyptian hatcher in his long experience has learned 
just about, how much airholes and smudge fire are necessary 
to get results. With these kept constant and the atmosphere 
constant, we have more nearly perfect conditions of incubation 
than are to be found anywhere else in the world, and I do not 
except the natural methods. The climatic conditions of Egypt 
cannot be equaled in any other climate, but as will be shown 
in the last section of this chapter, their effect can be dupli- 
cated readily enough by modern science and engineering. 
Mr. Edward Brown, who was sent over here by the English 
Government to investigate our poultry industry, was greatly 
87 
