456 S. F. Peckham—The Pitch Lake of Trinidad. 



of asphalt water shows it to be very rich in sulphates. As has been 

 elsewhere shown, sulphates, especially those of the alkalies, when 

 in solution are decomposed, when the water containing them flows 

 through strata impregnated with organic matter, into hydrogen 

 sulphide, and a carbonate of the oxide present. When hydrogen 

 sulphide infiltrates strata containing carbonate of lime, gypsum 

 is formed and sulphur deposited, or converted into free sulphuric 

 acid.^ 



The Miocene bituminous strata of Southern California are full 

 of sulphur springs and numberless deposits of sulphur. One such, 

 deposit in the southern part of Kern County is supposed to contain, 

 several thousand tons of sulphur. 



The reaction between sulphates present in the lake water and 

 the bitumen or other organic material of the formation furnishes 

 a ready explanation of the presence of hydrogen sulphide ; but 

 I must confess that the odour of that gas was much less apparent 

 about the lake than I had been led to expect. Analysis will alone 

 show what the gases are that inflate the asphalt, but of their 

 presence in enormous volume there can be no question. At a 

 rough estimate, I should say that from one-third to one-half the 

 volume of the mass as it exists in the centre of the lake is gas. 

 I also hazard the opinion that this gas makes the mass specifically 

 lighter than water, else the tables described by Manross and 

 Kingsley would not rise and spread on the surface of the water, 

 and further the masses of asphalt would coalesce, and the water 

 would float upon the asphalt. Moreover, it is without any doubt 

 that through this motion or ebullition which is produced, not by 

 escajDe of vapour generated by heat, but by gases" forced upward 

 by their own specific gravity through a yielding mass, that the 

 asphalt and mineral matter which forms the floors and sides of the 

 crater are mixed together until the asphalt is saturated ; i.e. it 

 reaches such a condition of plasticity and viscosity, that it will 

 no longer absorb any more mineral matter in presence of water. 

 I cannot account for the almost uniform character of the mixture 

 of water, bitumen, and mineral matter on any other hypothesis." 



Asphalt is very inert to changes of temperature. It is a very poor 

 conductor of heat, and even under a tropical sun the daily surface 

 changes of temperature and consequent expansions and contractions 

 are wholly inadequate to produce conditions affecting such enormous 

 masses of material as the crater contains. 



The frequent use of the term " volcanic " in connection with 

 the supposed origin of this mass of bitumen is, in my judgment, 



1 Proc. Amer. PMlos. Soc, vol. x, p. 445. BiscliofP, Chem. and Phys. Geol. 

 (Cav. Soc. Ed.), ii, p. 28 ; ibid., vol. i, pp. 15, 340. T. S. Hunt, Chem. and Geol. 

 Essays, pp. 23, 87, 99, 111. 



2 Mi\ Richardson asserts that 90 per cent, of the 80 per cent, of insoluble mineral 

 matter in the pitch is silica. As a possible explanation of the presence of so much 

 silica, I would suggest that the hot water that distilled the bitumen might have 

 held silica in solution, which has been precipitated within the pitch as it has cooled. 

 The fact, if it be a fact, that so much silica exists in the pitch as hydrate, may 

 account for the large amount of water held in the pitch. 



