Professor Haughton's Geology. 203 



which Mr. H. Woodward made an excellent drawing, which 

 we published in November, 1863. 



A student not duly cautioned against the deficiencies of 

 Professor Haughton's book would be grievously misled by his 

 remarks on the total thicknesses of different strata, and the 

 periods of geological time which they -represent. He takes 

 what he calls ' ' Azoic rocks," in which he seems to include 

 the formation containing the Eozoon Ganadense, to be 4'333 

 geographical miles thick, the Lower Palaeozoic 5*082, the 

 Upper Palaeozoic 4*458, and the Neozoic 4*512 ; and as these 

 figures approximately coincide, he says, "It is therefore ex- 

 ceedingly probable that these four great periods of the earth's 

 history are of nearly equal value in point of duration." In this 

 calculation no notice is taken of the breaks in the succession of 

 the various strata, and the consequent gaps in the records 

 which the geologist has to decipher. If we knew from phy- 

 sical reasons, that at a given number of millions of years ago 

 every portion of our globe was too hot for the existence of any 

 organized creatures analogous to those now living upon it, we 

 should be justified in stating that previous to that time all 

 formations would belong to the lifeless or Azoic age; but 

 notwithstanding the repeated proof of the vanity of arriving at 

 this class of positive decision upon merely negative evidence, 

 Professor Haughton endeavours to fix in the minds of his pupils 

 a philosophy which is obviously unsound. It happens, and may 

 happen to an extent far greater than is yet known, that leaves 

 and chapters of the Stone Book, wanting in some editions, 

 may be supplied in others — that is to say, for example, that 

 strata omitted in England are or may be detected elsewhere ; 

 but there is little hope that a complete series will be made 

 out, and as the matter at present stands, the gaps are of 

 immense importance when we have to consider either the 

 time spaces represented by groups of formations, or the changes 

 that have been experienced by the organic life of the globe.* 

 Professor Huxley has shown that it is common to make a great 

 exaggeration in speaking of the differences that are traceable 

 when existing plants and animals are compared with those of 

 past geological epochs. He says,t "We are all accustomed to 

 speak of the number and extent of the changes in the living 

 population of the globe during geological time, as something 

 enormous ; and indeed they are so, if we regard only the 

 negative differences which separate the older rocks from the 

 more modern, and if we look upon specific and generic 

 changes as great changes, which from one point of view they 

 truly are. But leaving the negative differences out of con- 



* See " Missing Chapters of Geological History," in our vol. yi., p. 12. 

 f Quarterly Journal Geological Society, May, 1862, p. xlviii. 



