EVAPORATION.--All liquids have the property known as vaporization, and will change their form into a gaseous state at ordinary temperatures. All solids will vaporize, if sufficient heat is applied. But at the ordinary temperature, with which we have to deal, in considering the use of carbureters, air is the factor which facilitates the process. AIR SATURATION.--Gasoline, confined in a vessel, will vaporize up to a point where it completely saturates the air contained therein, and then ceases. If allowed to stand in the open air, it will, in time, entirely evaporate. This is true of water, also. It is well, in this connection, to observe another thing. If the same quantity of liquid is placed in two separate vessels, one very tall, with a small surface of air in contact with the two surfaces, and the other vessel very shallow, so it has a large surface in contact with air, the latter will produce the most speedy evaporation. This shows that contact with air is the factor of the greatest importance in making a vapor. AIR CONTACT WITH GASOLINE.--The office of a carbureter is to provide the proper amount of air to the liquid fuel,--that is, up to that point where it can be utilized as a fuel to the best advantage. If a drop of gasoline, in one case is broken up into five hundred tiny particles, and in the other case into one thousand, it is obvious that in the latter case the air comes into contact with double the surface of the liquid than in the former case, hence will be so much more efficient, for the following reason: _Perfect combustion_ is the desired object in the engine cylinder. The more nearly the vapor approaches an impalpable gas the quicker will it ignite. Furthermore, the more intimate the air and the vapor are mixed the better will be the explosion or combustion. COMPRESSION.--The compression of the carbureted air in the engine cylinder performs certain very important things: When any gas is compressed the temperature is increased, the theory being that at each compression to one-half its volume, the temperature is increased double its former heat. If, therefore, compression in a cylinder reaches, say, 90 pounds, the heat set up is sufficient to instantaneously break up the small globules of gasoline, and at the same time produce a more intimate unity, which tends to make a more efficient mixture than would be possible without the compression. COMPRESSION AS A MIXING MEANS.--It will also be understood, that compression permits the bringing together of a much larger amount of fuel at each charge than would be possible without it, so that the two factors, namely, the volatilizing action of the air, the mixing of the air and vapor, and the compression, all serve to mix together the elements which will produce an explosion when the proper heat is finally applied.