282 CHEMICAL DISCOVERY ANp INVENTION 



of burning and lubricating oils by distilling shales and other 

 low-grade coal-like minerals was introduced in 1850 by James 

 Young of Kelly, and it is probable that the recognition of the 

 similarity between these oils and the natural petroleum led to 

 experiments on the latter. It was soon found that on distillation 

 a number of useful products could be obtained, including oil 

 suitable for burning in lamps and a denser oil applicable as a 

 lubricant and preservative to machinery. 



The extraction of petroleum from the earth is accomplished 

 by operations which are very simple in principle, and which 

 have not changed in fundamental character during the sixty to 

 seventy years since the commencement of the industry in the 

 United States. Petroleum is usually associated with more or 

 less salt water, and the strata which contain it are commonly 

 charged with inflammable gas often existing there under enor- 

 mous pressures. It may, however, happen that one of these 

 products may exist without the others, and either salt water 

 alone, or gas alone may be obtained when oil was expected. 



The first business in commencing to bore for oil is the erection 

 of a wooden structure, called the " derrick," about 70 feet high, 

 tapering upwards from a base of about 20 feet square to about 

 4 feet square at the top (Fig. 78). 



The derrick has a wheel at the top over which passes a rope 

 which hangs vertically and carries the steel boring tools at one 

 end, while the other end, by means of an arrangement worked 

 by a steam-engine, placed at a little distance from the derrick, 

 is alternately pulled and let go, so that the tools are alternately 

 raised and dropped in an iron tube previously inserted upright 

 in the ground. The tools have various forms according to the 

 character of the rock which has to be pierced. From time to 

 time the tools are lifted out of the pipe, and a " sand pump " is 

 introduced in order to withdraw the pulverised rock and sedi- 

 ment at the bottom of the hole. 



The wells thus sunk vary in depth in different oil fields, those 

 in Pennsylvania ranging from 300 feet to 3700 feet (Redwood). 

 In a district which has been found to be productive the borings 

 of wells soon multiply and the numerous derricks form a curious 

 and striking feature in the landscape. This is shown in the 

 accompanying pictures. An early stage is shown in the erection 

 of a derrick in a new field in Southern Russia (Fig. 78), and 

 when compared with the other pictures it will be seen that in 



