40 CONSTRUCTION AND MANAGEMENT OF SMALL GASWORKS. 



good working result. The arches may be both narrower 

 and lower than is usual in works of average size, because 

 too much space round the outside of the retorts means a 

 waste of fuel. There should not be more than is necessary 

 for the proper circulation of the furnace gases. The waste 

 of heat by radiation, also, is in some proportion to the square 

 feet of surface in the setting, and will not be so great with a 

 small as with a larger setting. There is no economy in 

 putting in larger arches than are, for the present, required, 

 in view of some indefinite future requirements, such, for 

 example, as an arch large enough for five retorts and setting 

 only two in it. The economy in structural cost is more 

 than offset by bad working results, and it is better to put 

 down no more than is wanted for present requirements, 

 and to replace when necessary. 



Taking the designs all round, there is apt to be too much 

 blind imitation of the practice at larger works. Two beds 

 cannot be run as a fraction of twenty, as the circumstances 

 are altogether different. If the working manager has pre- 

 viously held an appointment as engine house hand, or one 

 of a retort house gang, he is apt to overlook this point. 

 Six, five, or even four-hour charging may prove best when 

 the retorts can be run continuously, but with a scale of 

 operations too small to admit of this being done, there is 

 room for considerable skill in deciding upon the best con- 

 ditions as to hours of charging and weight per charge, that 

 will minimize idle time and banking up. Another problem 

 peculiar to the small works at certain seasons of the year is 

 whether it pays to run a bed of four on three charges per 

 twenty-four hours, and bank up at night, thus avoiding the 

 necessity for a second " hand," or a bed of three on four 

 charges per twenty-four hours, which cannot be managed 

 with less than two men. It is a question of fuel and wear 



