MECHANICS AND USEFUL ARTS. 25 



cleansing of the bars is also effected by this motion : the bars 

 have a stroke of about 3 inches, and we find in the average of 

 cases that a complete stroke about every 2 minutes is sufficient 

 to give the progressive motion necessary to maintain a proper 

 thickness of fire. As the bars themselves form an important part 

 of the machine, we have found it necessary to make special pro- 

 vision for their preservation. Each movable bar is provided with 

 a trough containing water, and there is a centre rib cast on each 

 bar which is immersed in the water. The other part of the bar 

 forms a perfect cover for the trough to exclude ashes, etc. ; these 

 troughs are supplied with water from a small cistern, and the 

 level is maintained by a very sensitive float and valve. In conse- 

 quence of the slow motion of the machine, veiy little wear and 

 tear occurs in the working parts. There is no part of the appa- 

 ratus exposed to any injurious action of fire except the upper sur- 

 face of the bars, and these are effectually protected by the trough 

 arrangement. Our experience shows that with moderate care 

 the amount of wear and tear is not greater than what occurs in 

 most ordinary furnaces. 



" With regard to the economical results obtained, you will find 

 some particulars given in our circular. As compared with the 

 best hand-firing, where ordinary fuel is used, the results do not 

 exceed 10 to 12 per cent. We find that the system adopted by 

 the careful stoker and the machine system are very similar. In 

 both cases frequent charges at short intervals are adopted instead 

 of heavy charges at longer intervals ; but, in the case of hand- 

 firing, the incessant opening of the doors, and the interruptions 

 caused by cleaning the bars, are drawbacks that are avoided in 

 the machine. Of course, when the machine is compared with 

 ordinary random hand-firing, its economical superiority is very 

 decided ; but the chief source of economy arises from our being 

 able to use the smallest and cheapest fuel, fuel much of which 

 cannot be used at all in ordinary hand-fire furnaces. The saving 

 from this cause varies in different districts, and will range.from 

 20 to 100 per cent. In most cases, perhaps, the appreciation that 

 leads to the adoption of any machine or system is the most satis- 

 factory evidence of its value ; yet this is not a rule without 

 numerous exceptions, and on no subject is there more reasonable 

 ground for a justifiable scepticism as to the merits of any remedy 

 that may be propounded than that of smoke prevention. For 

 many years the public have had plans constantly brought under 

 their notice that were to end the nuisance arising from smoke, 

 but it still continues a very substantial nuisance, and appears to 

 have a very wonderful vitality. As evidence of approval of the 

 furnace, I may state that since we commenced manufacturing this 

 form of furnace, about 18 months ago, we have fixed and put 

 to work more than 120, with the most satisfactory results, and 

 approval of the furnace is extending. We are at present sending 

 out more than 20 per month ; in the town of Bradford alone, 

 which appears to be taking the lead in the enforcement of sanitary 

 improvements we have orders for between 50 and 60 furnaces in 

 a single street or road, Thornton Road. 



