34 HATCH : THE KOLAR GOLD-FIELD. 



Of late Indian coals have practically superseded English, the 

 result being a considerable saving, which varies, however, according 

 to the prices ruling. Barakar coal from the Bengal Presidency has 

 been used principally, but Singareni coal from Hyderabad is com- 

 ing into favour. The Singareni coal has slightly less ash and less 

 clinker than the Barakar. It is preferred by the native firemen 

 because they find the work of firing is lighter. The cost of the three 

 coals is at present as follows :— 



M a. 



English . . . . . . . . 32 o per ton. 



Barakar . . . , . . . . 18 15 „ 



Singareni . . . . . . . . 15 8 ,, 



The consumption of Indian coal per indicated horse-power in 

 the most effective steaming plant, e.g., that of the Mysore mill- 

 engines, is about 47 lbs. per hour, boiler-pressure being maintained 

 at 80 lbs. per square inch. The average throughout the field is, 

 however, about 6 lbs. per hour. 



Prime Motors. — The prime motors employed on the Kolar gold- 

 field may be classified as follows : — 



1. Air-compressing engines. 



2. Engines for driving stamps, crushers, Wheeler pans, etc. 



3. Hoisting engines. 



4. Cornish pumping engines. 



AlR-COMPRESSORS. — Power is transmitted by the medium of 

 compressed air to the machinery employed underground. From the 

 receivers the air is carried down the shafts in 8 or 6-inch wrought 

 iron mains ; and underground is distributed to the different points 

 at which it is required by 4 and 2-inch pipes. 



The air-compressors at present in use on the gold mines are 28 

 in number, having an aggregate indicated horse-power of 3,450. 

 They are chiefly of Walker Brothers' manufacture. The air is com- 

 pressed either in one or two stages. At the Mysore Mine there are 

 two single-stage (20-inch air-cylinder) and three double-stage com- 

 pressors, supplying air to 60 rock-drills (Climax pattern), of which 

 an average of 55 are at work, 14 donkey-pumps (Cameron's) and 

 three airhoists. 



