How to Keep Eggs for Incubation.
The above is only one case out of many that are constantly taking place. In nine cases out of ten, failure with good machines may be traced directly to the operator or the eggs. Occasionally there is a defect in a machine overlooked by the maker, which he is in honor bound to make good.
The best way to secure good eggs is to engage them beforehand from reliable parties, who will gather them carefully several times each day in cold weather to prevent them chilling, and turn them at least every other day. If these eggs are kept on end it is not necessary to turn them as often.
I have egg boxes for the purpose, in which the eggs are set on end, like the common market box. These boxes and contents can be turned as readily with a dozen as when full. Eggs intended for incubation should always be kept in a cool place,—duck eggs especially,—as the fertile eggs will change at a temperature of eighty-five to ninety degrees, and spoil within three or four days. One may safely calculate on one-half of them being spoiled in a week at a temperature of 80 degrees. All kinds of eggs can be safely kept three weeks for purposes of incubation, say, at forty-five to fifty degrees, though I always like to have them as fresh as possible.
In filling orders for eggs at a distance I make it a point never to send eggs more than four days old, or with less than seventy-five per cent of fertility. Transportation, even over rough roads, does not affect their hatching, except in extreme warm weather, when the contents, becoming thin and slightly evaporated through the heat, are apt to mix, when they will surely cloud and rot. I have often sent eggs 2,000 miles, with the report that every egg produced a duckling. With machine ready and running steadily the eggs may be introduced at once. They need no moisture now, and it is not necessary to disturb them for the first forty-eight hours.
How to Choose and Use Thermometers.
Place your thermometer on the eggs in middle of egg-tray. Be sure, in the first place, that you get a good glass, as all depends upon its accuracy. Do not use one with the mercury bulb lying upon a solid metal plate, as the refraction of heat upon the plate from the tank above will always run that glass one or two degrees higher than the heat in the egg-chamber, but get one, if possible, with a hole in the plate opposite the bulb, so that the heat can play around the bulb and through the plate, giving the correct heat of eggs and chamber. Do not hang your glass up over the eggs, or put it down between the eggs, but lay it on them, for the reason that, though either of these positions may be all right during the first twelve days of the hatch (if your eggs are fertile), they will surely be all wrong during the last part.
I will endeavor to explain this thing, so that the novice will understand how important it is. Before circulation begins in the embryo chick or duck, and there is no animal heat in the egg, the temperature of the egg chamber regulates that of the eggs. But after circulation begins, and especially during the latter part of the hatch, when the rapidly-developing young bird throws out a great deal of heat, the thing is often completely reversed. For instance, a glass may be hung one inch above the eggs and another placed immediately on the eggs beneath. The one above may register 102 degrees; the one below, on the eggs, will register 105 degrees,—conclusively showing that the eggs are now, by their own caloric, heating the egg-chamber.
I have often, during the last part of a hatch, when the thermometer was ranging from 70 to 80 degrees outside of machine, placed a glass on the hottest part of the boiler, where but one lamp was dimly burning, carefully covering the glass. In that position it would register perhaps 96 to 98 degrees, while a glass inside the machine, and on the eggs, would register 103 degrees, proving beyond a doubt that the eggs, by their own caloric, were not only heating the egg-chamber, but contributing their quota towards heating the water in the tank. Now, who will pretend to say that a glass hanging above the eggs will give the correct heat of the egg after circulation begins. So that, even in cold weather, the amount of oil consumed during the last week of the hatch is less than half the amount required during the first part.
The operator must not expect the eggs to heat up at once. On the contrary, they will cool the air in the egg-chamber very sensibly, though they will not affect the heat of the water in the tank. It will be from five to eight hours before they arrive at their normal heat.