280 SKETCHES OF CREATION. 



no productive and paying well has ever been opened in 

 this formation. 



The Niagara limestone has proved locally a similar 

 cause of mistaken ventures. In the neighborhood of Chi 

 cago some of the beds of this limestone are eminently bi 

 tuminous. Chicago has several times made discoveries 

 which were destined to enrich her if we could believe 

 the newspaper accounts of the amount of fatness in her 

 rocky substratum. Indeed, &quot;the spirits&quot; themselves, in 

 looking down through the rocks which underlie the city, 

 were egregiously humbugged by this rock &quot; of color.&quot; 

 Samples of this Chicago humbug may be examined in the 

 old ivy-mantled and oil-bedraggled walls of the Second 

 Presbyterian Church in that city. The oil fried out of 

 the rock by the summer s sun has admirably imitated the 

 dusky brush of antiquity, as modern art has learned to im 

 itate the time-scarred products of the pencil of a Rubens 

 or a Raphael. 



The Coal-measures, also, from the wide-spread belief that 

 they are the source of native petroleum, have been faith 

 fully explored and expensively bored, with scarcely better 

 success than in the Corniferous limestone. There has hard 

 ly been a good well that is known to have been supplied 

 from the Coal-measures. 



Crude petroleum is not a product of definite composi 

 tion. It seems to be a varying mixture of several hydro 

 carbons, some of w r hich, as naphtha, volatilize with rapidi 

 ty when exposed to the atmosphere ; others, as kerosene, 

 slowly ; while others, as bitumen, are nearly fixed. It con 

 tains also varying quantities of aluminous matters and oth 

 er impurities. 



It occurs in stratified rocks of all ages, from the Lauren- 

 tian to the recent. It has even been observed in some 

 rocks of a granitic structure. The mere presence of petro- 



