294 ORDER AND SUCCESSION OP LIFE. 



the higher animals at least, by the subtler promptings of 

 the intellect and reason. In the one case we deal with 

 forms and forces that are extraneous j in the other, with 

 those to which we ourselves belong, and hence the higher 

 the interest excited, and the deeper the mysteries involved. 

 What is life 1 Whence its origin ? And how has it mani- 

 fested itself during the long ages throughout which geology 

 has traced its presence in the rock-formations of the globe 1 

 These are questions of the highest interest to science, and 

 how feeble soever the indication towards a solution which 

 human knowledge can offer, every tracing is of value so 

 long as it is founded upon fact, and sketched by an honest 

 hand. Such is the aim of the present Sketch a deduction 

 from the statements in the preceding chapters, a digest of 

 the discoveries of palaeontology, an indication, if not of the 

 nature and relations of life, at least of its order and succes- 

 sion as warranted by the truths of Geology. 



Concerning the origin of life, Geology ventures no opin- 

 ion. It may have started into being at the immediate 

 fiat of the Creator, or it may have arisen through secondary 

 causation, acting in obedience to Creative Law. It may 

 have sprung from a single primordial germ, or it may have 

 spread from several primordial sources. In its essence it 

 may be a thing per se, or it may be merely a manifestation 

 arising from the interactions of the subtler physical forces. 

 On such points Geology offers no opinion. It deals with 

 life as it finds it, and dates its commencement with the 

 earliest traces yet discovered in the stratified formations. 

 At one time this limit was found in the lower Silurians, 

 more lately in the Cambrians, and now, as we have seen in 

 Sketch No. 5, discovery has carried it back to the Lau- 

 rentian system a suite of strata of much higher antiquity. 

 Whether these Laurentian rocks are the oldest or earliest 

 in which traces of life can be detected, Geology does not 



