Early Designs One problem with early the still air design was maintaining equal and proper temperatures throughout the egg chamber as the eggs radiated heat releasing carbon dioxide. Due to the amount of heat that the chick would produce the success of still air incubators would rely on a means of being able to automatically make adjustments to heightened temperatures as incubation progressed. Mercury and gas regulators were used in the early stages. If the incubator was too hot the flame could be reduced or raised if the incubator cooled. Problem was a cold draught would cool the incubator quickly before the regulator could supply the heat. All required persistent monitoring. With the development of temperature regulators started by Cornelius Drebbel in 1600 a more effective means of temperature control was added. In 1750 French scientist de Beaumur used radiant heat methods of the Egyptians. By using fermentation to heat the incubator and the early type thermostat invented by Drebbel.   Dampers or vents could be opened allowing for the release of heat, or when the chamber was opened for turning of the eggs. Some were designed with dampers that were at the bottom to receive cool air and were activated by the regulator installed. Hearson would soon contribute by installing an automatic temperature regulator within the incubator. But the still air or hot water incubators did not allow for settings at different intervals. There were no means of compensation for early developing embryos. The only ventilation for some would be the opening of the chamber to turn the eggs at intervals. Over 100 years of design and experimentation led to at least seven different "still air" incubators for sale in 1885. By 1919 there were about 50 different types being offered, all based upon the same principals but having different designs with electric thermostats. Most were capable of hatching 200 eggs in one hatch. What we see is a design established for the small breeder or farm holder. England seemed to prefer the hot water incubators in part due to the fuel shortages that often plagued the European economy. What is note worthy about the work that was done in Europe with the hot water incubators was the contribution to science for premature infants, based solely off the inventions and inventors of poultry incubators. What will undoubtedly change the success of the artificial incubator will be the electric "forced draught" or " forced air" incubators.   This still air Incubator has a damper door placed at bottom to release hot air and accumlated gasses while allowing fresh cooling air in.