340 Sir Boverton Redwood [June 7, 



various oil-fields of the world is that which is known as percus- 

 sion drilling. The plant consists of a tall pyramidal wooden, or 

 occasionally steel, structure, sometimes as much as 80 feet in height, 

 with an engine-house attached. This model, beautifully carved by 

 Burmese natives, gives a good idea of the plant, notwithstanding 

 the artistic disguise, for it is made to scale. The "string," as it is 

 called, of drilling-tools consists of the " bit " or cutting-chisel, the 

 " auger-stem," the " jars," and the " sinker-bar." Some idea of the 

 nature of the work to be done may be formed when it is stated that 

 the length of a standard deep-drilling Californian string of tools is 

 over 60 feet and the weight 2^ tons. The bit alone, for a bore-hole 

 of 23 inches diameter, of which a full-sized model, kindly made for 



i 



Fig. 2. — Burma, Oil Well. 



me by the Oil Well Supply Company, is in front of the lecture-table, 

 has a length of 6 feet and weighs over a ton. The string of tools is 

 suspended by a manilla cable or wire rope from one end of an 

 oscillating beam, the other end of which is connected by a rod with 

 a crank on a shaft driven by the steam-engine. It is thus caused to 

 rise and fall, so that the bit delivers a series of blows on the rock at 

 the bottom of the well, the tools being gralually lowered as the depth 

 increases. The jars may be l)roadly likened to a pair of flattened 

 links of a chain, and its function is to strike an upward blow when 

 the bit l)ecomes jammed in the rock. From time to time the string 

 of tools is drawn up into the derrick, and the detritus is removed 

 from the borehole bv the use of a valved cvlinder, termed a sand- 



