THE GOVERNOR, which can be dispensed with in most ordinary domestic acetylene lighting installations provided with a good gasholder of the rising-bell type, is designed to deliver the acetylene to a service-pipe at a uniform pressure, identical with that under which the burners develop their maximum illuminating efficiency. It must therefore both cheek the pressure anterior to it whenever that is above the determined limit to which it is set, and deliver to the efferent service-pipe acetylene at a constant pressure whether all or any number of the burners down to one only are in use. Moreover, when the pressure anterior to the governor falls to or below the determined limit, the governor should offer no resistance--entailing a loss of pressure to the passage of the acetylene. These conditions, which a perfect governor should fulfil, are not absolutely met by any simple apparatus at present in use, but so far as practical utility is concerned service governors which are readily obtainable are sufficiently good. They are broadly of two types, viz., those having a bell floating in a mercury seal, and those having a diaphragm of gas-tight leather or similar material, either the bell or the diaphragm being raised by the pressure of the gas. The action is essentially the same in both cases: the bell or the diaphragm is so weighted that when the pressure of the gas exceeds the predetermined limit the diaphragm or bell is lifted, and, through an attached rod and valve, brings about a partial closure of the orifice by which the gas flows into the bell or the diaphragm chamber. The valve of the governor, therefore, automatically throttles the gas-way more or less according to the difference in pressure before and after the apparatus, until at any moment the gas-way is just sufficient in area to pass the quantity of gas which any indefinite number of burners require at their fixed working pressure; passing it always at that fixed working pressure irrespective of the number of burners, and maintaining it constant irrespective of the amount of pressure anterior to the governor, or of any variations in that anterior pressure. In most patterns of service governor weights may be added when it is desired to increase the pressure of the effluent gas. It is necessary, in ordering a governor for an acetylene-supply, to state the maximum number of cubic feet per hour it will be required to pass, and approximately the pressure at which it will be required to deliver the gas to the service-pipe. This will usually be between 3 and 5 inches (instead of about 1 inch in the case of coal-gas), and if the anterior pressure is likely to exceed 10 inches, this fact should be stated also. The mercury-seal governors are usually the more trustworthy and durable, but they are more costly than those with leather diaphragms. The seal should have twice or thrice the depth it usually has for coal-gas. The governor should be placed where it is readily accessible to the man in