(1.) The motive-power to be employed in producing electricity and its applicability for the purpose. (2.) The description of machinery to be employed. (3.) The value of the light produced, and its adaptability to the requirements of any town. (4.) The comparative cost of the electric light as compared with gas. (1.) Whatever motive power is employed, whether water-power, steam or gas, it is essential that it should be steady and unfailing; steady, because the regularity and uniformity of the light depends upon the evenness of the speed with which the power works, and unfailing, because a stoppage means the immediate extinguishment of the lights: electricity, unlike gas, is not stored after manufacture, but is used as fast as it emanates from the producing power.[116] Sensitive governors and careful bedding of the machinery greatly tend to lessen unsteadiness, and are points of considerable importance. (2.) The machinery consists of the dynamo machines, the conducting wires and the lamps. I will not here enter into the question of which is the best dynamo machine to employ, as to discuss the merits of them all would involve a large amount of space; but for this and other valuable information upon the subject of electric lighting I will refer my readers to Mr. Hedges’ excellent little book entitled ‘Useful Information on Electric Lighting,’[117] but the following points should be attended to. The dynamo machine should be fixed in a dry place, and not be exposed to dust or flyings, it should be kept perfectly clean, and its bearings well oiled, its coils and conductors should be perfectly insulated, and it should, where practicable, be fixed on an insulated bed. With regard to the wires, the following ‘Regulations for the prevention of Fire Risks arising from Electric Lighting,’ published by the Society of Telegraph Engineers and of Electricians, are given in full, as they leave nothing to be desired in the way of their careful selection and fixing: “(7.) Every switch or commutator used for turning the current on or off should be constructed so that when it is moved and left to itself it cannot permit of a permanent arc or of heating, and its stand should be made of slate, stoneware, or some other incombustible substance. “(8.) There should be in connection with the main circuit a safety fuse constructed of easily fusible metal which would be melted if the current attain any undue magnitude, and would thus cause the circuit to be broken. “(9.) Every part of the circuit should be so determined that the gauge of wire to be used is properly proportioned to the currents it will have to carry, and changes of circuit, from a larger to a smaller conductor, should be sufficiently protected with suitable safety fuses, so that no portion of the conductor should ever be allowed to attain a temperature exceeding 150° F.