"So it would; and when you can produce a machine with a perfect uniformity of heat in the egg-chamber, I should be most happy to use an automatic tray, but I have never yet seen that machine." In our own double-cased Monarch, in cold weather, there is at least one degree difference between the end and centre of egg-tray. In single-cased machines this difference must be largely increased, and in automatic trays the eggs must necessarily remain where they are placed through the entire hatch. Now, under these conditions, if the heat is right in the centre of trays it must be all wrong in the ends. The hatch will be protracted long after the proper time, and if those on the ends of trays come out at all it will be forty-eight hours behind time and with weakened constitutions, keeping one in constant stir with their sickly plaints. It is needless to say that there is a great mortality among birds of that description, and at the end of ten days they are usually among the things that were. Hatching the Eggs. The next thing is testing the eggs. This matter is essential as well as economical, with both hens and incubators. I once knew a man who ran a six hundred-egg machine for three weeks on one fertile egg. The other 599 proved infertile, and he did not know it until they refused to hatch at the end of three weeks--a great waste of oil, but a greater waste of time,--three whole weeks in the best part of the season. Another man kept forty hens sitting three weeks with an average of one fertile egg to each bird, when three of them could have done all the hatching just as well, and then, at the end of four days, could have had the rest put upon better eggs. A great waste of hen power, you will say, with time lost, together with forty dozen eggs, which would have been just as good for table use had they been tested out in four days. It often happens in the winter, when eggs are apt to be infertile, that, after testing the contents of four trays, they can be contained in three, when the other can be filled with fresh eggs. Here is where the advantage of adjustable trays comes in. Often the operator running a large machine has not eggs enough to fill it without a part of the eggs becoming very old, and also losing ten or twelve days of valuable time; with the adjustable tray, eggs can be introduced at any time, and the same heat preserved on all. I usually test duck eggs at the end of the third day. The fertile germ is then plainly visible, and the eggs can be passed before the light, several at a time.