1898.] PECKHAM — THE GENESIS OF BITUMENS. 125 



the occurrence of bitumens and the relation of such occurrence to 

 their probable origin. 



Leaving the problems of orography to the physical geologist for 

 solution, there are a few suggestions to be made relating to these 

 problems that I have not seen anywhere mentioned. If we regard 

 the dizzy heights of the Andes and Himalayas, or the profound 

 abysmal depths of the Pacific as isolated phenomena, they appear 

 on a scale of oppressive grandeur and immensity ; yet these irregu- 

 larities in the earth's crust reach a maximum of only about ten 

 miles in vertical height, which is only one twenty-five hundredth or 

 four hundredths per cent, of the circumference of the earth at the 

 equator. The local foldings of a few hundreds of feet in disturbed 

 strata are microscopic when compared with the earth's diameter ; 

 and yet we are accustomed to regard these plications of strata as the 

 result of sudden movements in the earth's crust. This is a pure 

 assumption. The period of time through which critical observa- 

 tions of geological phenomena have been made when compared 

 with the time that has elapsed since life dawned upon the 

 earth is also microscopic; it is a smaller fraction than four 

 hundredths per cent. The element of time in geological phe- 

 nomena is only just beginning to be appreciated. We have learned 

 from a few years of observation that some continental masses are 

 rising and others falling with reference to the sea level ; yet no 

 one has observed these movements through many centuries, nor 

 have these vertical movements of the coasts of the world been co- 

 related and the laws that govern such movements been determined. 

 We do not know whether a continent has emerged from an ocean 

 maintaining a constant level, or whether the ocean has receded as 

 the contracting mass has rendered the ocean depths more profound, 

 or, as is more probable, the shrinking of the crust has changed the 

 distance of the ocean surface from the centre of the earth, render- 

 ing the elevations apparently greater. It is not material to this 

 question that we should know. Nor is it of importance to consider 

 whether the continued operation of forces at present active through 

 countless centuries, or the repeated interjection of cataclysms of 

 world disaster, has brought the earth to its present condition. Vol- 

 canic eruptions, earthquakes and floods, separately and unitedly, 

 change the face of nature within our own generation ; it is reason- 

 able to suppose that they have acted from the earliest period of the 

 earth's history to the present time with constantly lessening vio- 



