The Dollar Hen

by Milo Hastings

The attempt just referred to was made several years ago by one of the most successful of incubator manufacturers and because of his failure other inventors were inclined to steer clear of the proposition. Meanwhile the need of such an incubator has grown enormously. At the time that above effort was made no duck ranch existed whose annual production ran over thirty or forty thousand ducklings, whereas we now have several in the one hundred thousand class.

Much more remarkable has been the growth of the day-old chick business. The discovery that newly hatched chicks could be successfully shipped hundreds of miles with less loss than shipping eggs for hatching, has resulted in a few years' time in the growth of hatcheries of considerable size where chicks are hatched by means of common incubators. Still another opportunity for the use of large hatcheries has been by the growth of poultry communities. There are other communities besides those mentioned in this book which would amply support public hatcheries. If half the poultry growers of Lancaster County, Pa., were to be prevailed upon to patronize a public hatchery, the county would support between fifteen and twenty 100,000 egg incubators. Any of the numerous trolley centers in Indiana, Ohio and Southern Michigan would likewise be profitable locations for the establishment of public hatcheries.

The demand for the incubator of large capacity has, within the last year or so, brought two or three "mammoth" incubators into the market. The devices I now refer to consist of a row of box incubators which, instead of being heated by single lamps, are heated by continuous hot water pipes. This scheme effects a considerable saving in fuel cost and labor, but the bulkiness of construction and the woeful lack of evaporation control are still to be dealt with.

The writer now wishes briefly to describe the plan of construction and operation of a new type of hatchery, the success of which has recently been made feasible by inventions and technical knowledge hitherto unavailable. The plan of the hatchery is on that of a cold storage plant as far as insulation and general construction go. The eggs are kept in bulk in special cases which are turned as a whole and may rest on either of four sides. At hatching time the eggs are spread out in trays in a special hatching room, which is only large enough to accommodate chicks to the amount of one-sixth of the incubator capacity, for twice a week deliverings, or one-third if weekly deliveries are desired.

There are no pipes or other sources of heat in the egg chambers. All temperature regulation is by means of air heated (or cooled as the case may be) outside of the egg rooms and forced into the egg rooms by a motor driven cone fan, maintaining a steady current of air, the rate of movement of which may be varied at will. The air movement maintained will always be sufficiently brisk, however, to prevent an unevenness of temperature in different parts of the room.

So simple is this that the reader will doubtless wonder why it was not developed earlier. The reason is that air subject to the climatic influences will, with any forced draft sufficient to equalize temperature, result in a fatal rate of evaporation. Sprinkling the air has not generally been thought practical because of the notion that air must not be used in the egg chamber but once, which involved quite a waste of heat necessary in warming a large bulk of air and evaporating sufficient water. Moreover, no means has, in the past, been available for making a sufficiently accurate measurement of the evaporating power of the air.

The hair hygrometers commonly sold to incubator operators are known by scientists to be absolutely unreliable. The range between the wet and dry bulb thermometers was found in the Ontario experiments to give readings with and without fanning that varied 15 to 20 per cent. in relative humidity which, at the temperature of an egg chamber, would amount to a variation of three to four hundred of vapor pressure units, which, with the forced draught plan, would ruin a hatch of eggs in a few hours. The sling psychrometer as used by the U.S. Weather Bureau should, in the hands of an expert, give results making possible measurements accurate to two or three per cent. of relative humidity or forty to sixty units of vapor pressure. In contrast with these blundering instruments we now have available an instrument with which the writer has frequently determined vapor pressure accurately to within a range of two or three vapor pressure units and the instrument is capable of being constructed for even finer work.

As it is only by means of air with the moisture content absolutely controlled that the use of a large room becomes possible, we can now see why this type of hatching remained so long undeveloped. By means of such vapor pressure control the large egg chamber is not only feasible but the rate of evaporation at once becomes subject to the control of the operator and we achieve a perfection in artificial incubation hitherto unattained.

The means by which the air moisture is regulated is similar to that used in up-to-date cold storage plants where the air is made moist by sprinkling and dried with deliquescent salts. The regulation of vapor pressure, like that of temperature, may be by electrically moved dampers which switch a greater or less proportion of the incoming current to the sprinkler or dryer as the case may be. The ordinary incubator thermostat gives the necessary impulse for the control of the temperature dampers, while the instrument above referred to is used for the vapor pressure control.

As the entire air circuit is closed, the chemical composition of the air may also be regulated at will. This results in a reduction of the quantity of heat required to a minimum; in fact, with the incubator in full swing, the air will, at times, need cooling rather than warming.