MINING 387 



According to the French regulations, safety catches, for holding the cage in the shaft, in 

 the event of a breakage of the winding rope, are compulsory, in this respect differing from 

 British practice. Many British inventors have during the past few years endeavoured to 

 provide a satisfactory catch, but the rope and rail guides almost universal at British collieries 

 are not suitable, and there is a considerable prejudice against the use of such appliances, 

 especially under the exacting conditions met with at many of the new collieries. Several of 

 the recently-opened shafts in Yorkshire and Nottinghamshire are equipped with four-decker 

 cages, capable of raising 70 men. On the Continent the practice is to sink a greater number 

 of shafts in proportion to the mineral area and the engines are designed for lower duties. 



At the Maltby colliery steel rail guides have been fitted across the centre of the shaft, 

 owing to the depth and increased demands of the loads. The cost per yd. was if6.i7s.8d. 



At modern collieries the use of hydraulic lifts at pit tops and bottoms is now general. 



BLASTING EXPLOSIVES. On May 21, 1912 the Home Secretary issued in England a 

 new order regarding the use and storage of explosives in coal-mines. The main features of 

 the order are the more detailed restrictions respecting the use of explosives in mines, the 

 standardisation of cartridges, regulation of the size of rock-drill bits, precautions to be 

 taken in the case of miss-fires, special stringent provisions for fiery mines, and regulations 

 in the case of sinking operations. After March 31, 1913, the standardisation of cart- 

 ridge diameters is made imperative. The sizes of drill bits are also specified, and this 

 is provided for by the regulation that the drill bit must afford a clearance exceeding the 

 diameter of the cartridge for which the hole is intended. The standard sizes of the cart- 

 ridges are to be |, - 1 /-, --^, Vs V inches, and the drill bits for each size must not be less in 

 diameter than | in. in excess. The diameter of a drill bit for the smallest permitted 

 size of cartridge must not be less than i in. 



In Belgium and France further tests have been carried out with a view to establish- 

 ing the safe limit-charges of explosives under varying conditions. 



The United States Government has for sonie time past conducted experiments at 

 their testing station at Pittsburg, in order to discover which of the many grades of short- 

 flame explosives possess the qualities that render an explosive most effective and least 

 dangerous for mining coal. As a result a " permissible " list has been issued. 



A new type of instantaneous fuze has recently been introduced known as "Cordeau 

 Detonant," or, "Cordeau Bickford," consisting of a core of trinitrotoluol enclosed in a lead 

 sheath, which has a speed about 15,000 feet per second. This requires a detonator to initiate 

 the explosion, but is sufficiently powerful in its action to 'induce detonation in a cartridge 

 through which it is threaded. It is largely used for certain experimental work as a standard 

 for comparing the speed of detonation of other explosives. 



DEEP MINING. Of all physical causes that underlie the development of mining the 

 question of depth may be said to be the most important and far-reaching. Its influence 

 upon the operations of winding and pumping, the methods of working, the transmission 

 of energy, ventilation, and last, but not least, the support of the surface, is of ever-in- 

 creasing gravity. The question of temperature is of particular importance. A differ- 

 entiation in the conditions of labour where abnormal temperatures are encountered is a 

 feature of recent industrial mining legislation, and in this respect the earlier example of 

 Germany has been followed by Belgium and France. By the new French regulations 

 work is prohibited in places where the temperature reaches 35 degrees C. on the dry 

 thermometer or 30 degrees C. wet bulb reading, but any temperature exceeding 25 de- 

 grees C. wet bulb is considered high. 



Some valuable records are given by G. J. Young as to the conditions encountered on 

 the Comstock lode (" Ventilating System at the Comstock Mines, Nevada," Trans. 

 Amer. Inst. of Min. Eng., Vol. 41, p. 3, 1910). He finds that moderately high- temper- 

 atures from 95 to 105 degrees F., with moderate humidities from 50 to 70 per cent rela- 

 tive humidity and with air currents of velocities from 200 to 300 feet per minute, do not 

 prevent work nor are particularly uncomfortable. A higher temperature, from no to 

 115 degrees, with high humidity and moderate velocity air-currents, very greatly im- 

 pairs efficiency, and a still higher air-velocity, under the same conditions, renders work 

 more bearable, though miners cannot work very long at one time. A moderately high 

 temperature, from 95 to 105 degrees in a saturated atmosphere with no current, becomes 

 very trying. Prolonged exposure with much exertion is dangerous. A moderate tern- 



