n8 THE HOUSE AND ITS EQUIPMENT. 



AIR-GAS IN THE COUNTRY HOUSE. 



The Demand for More Light Broad Principles of Air-gas Plants Motor Drive versus Weight 

 Drive Rich versus Weak Mixtures of Petrol and Air Costs of a Typical Small Plant. 



THE newest &quot; Darwinism &quot; asserts that environment has a greater effect than inherited faculties 

 on the development of the race. The almost &quot; cat-like &quot; sight whereby our great-grandmothers 

 could thread a needle by the light of a wax candle at the far end of the room has certainly not 

 descended to us, and every improvement in the quality of artificial light has resulted in an 

 immediate demand foi a greater quantity, till we are led to wonder what amount of light our 

 grandchildren will consider essential for their comfort. The problem of lighting the smaller country 

 house entered upon another phase with the advent of what we may call single-house lighting installations. 

 The householder who requires only some twenty-live or thirty lights in his house may be rather alarmed 

 at the idea of installing a miniature gasworks or electric-light station of his own ; but it is often to his 

 advantage to do so, even in places where there is a public supply. 



The apparatus used for the manufacture of air-gas is very simple and requires no skilled attendance ; 

 the plant described below is worked with complete success by the housemaid. Air-gas is merely a mixture 

 of petrol vapour and air. The difference between the mixture used in the cylinder of the motor-car engine 

 and that used in the burner of an air-gas system is simply that a much larger quantity of air is added in 

 the latter case, whereby it is rendered non-explosive. The broad principle on which most air-gas generators 

 work may be described as follows : A small motor drives an air-pump or blower which sucks or forces air, 

 either directly or through a small air-container, into a carburettor, where it mixes with the petrol vapour 

 and then passes directly to the gas pipes and burners, or into a small gas-container connected with the supply 

 pipes. The function of the container is to keep the pressure constant, so that those systems which use 

 an air-container do not require a gas-container, and vice versa. The motor takes various forms to suit 

 particular cases. Where there is a disused well available, or the clear side of a house wall, the gradual 

 falling of a weight, as in a grandfather s clock, can be made to drive the pump. If there is a cheap water 

 supply, a water motor can be installed for this purpose ; but the form of motor applicable to the case where 

 these conditions do not exist is a small hot-air engine driven by means of the gas it generates. A few 

 turns have to be given by hand to the motor at starting. This is sufficient to generate a little gas, which 

 j lasses to the burner under the motor cylinder. When this has been burning several minutes a few more 

 turns will set the motor running, and the rest of the control is entirely automatic. If it is desired that a 

 supply of gas shall always be available at times when the engine is not running, a small gas-holder of limited 

 capacity can be installed without adding greatly to the capital cost ; but this is rarely necessary, as 

 in most houses gas is only required during certain hours. An electric switch can be fixed in the house 

 holder s bedroom, or any part of the house, by means of which the engine can be stopped. This is found 

 to be an exceedingly useful contrivance by those who have tried it, saving as it does a visit to the engine- 

 house the last thing at night, such a visit being particularly tiresome on a dark winter night when the 

 engine-house is situated some distance away from the residence, as has happened in some instances we 

 have known. In the case of the weight-driven machines, when no gas is being used, an automatic inlet 

 valve cuts off the supply of air from the pump. The partial vacuum so created is sufficient to hold up 

 the weight, which ceases falling until the gas is turned on again, and the air inlet is automatically opened 

 in consequence. It should be noted, however, that with some plants the pressure of the gas drops when 

 the weight is wound up, and any burners in use at the time would probably go out. Care should therefore 

 be taken not to wind up the weight when gas is being used. 



The machines driven by water motors are usually provided with an automatic regulator, which 

 turns off the water supply and the gas when no light is on, and turns it on again as soon as the first burner 

 is lit. Some systems are arranged to use a gas much richer in petrol vapour than others. These 

 naturally require a less volume of gas to give the same light for a given time, so that the strength of mixture 

 adopted does not materially affect the cost of illumination. The advocates of a weak mixture claim that, 

 as all the air required for perfect combustion is supplied in the gas, no vitiation of the atmosphere takes 

 place. Those who favour the use of a richer air-gas and employ a Bunsen burner claim that the additional 

 air drawn in by the gas during combustion has a cooling effect on the burner and results in a longer life 

 for the mantles and fittings. Arrangements are made in most forms of generator for automatically 

 controlling the mixture of petrol and air and for keeping the proportions constant at the strength found 



