138 



THE GEOLOGIST. 



have been produced by the last great convulsion that has affected our planet."* 

 Omitting any opinion upon the cause of those deposits, Sir Charles Lyell gives 

 the following definition of the diluvium : " Those accumulations of gravel and 

 loose materials whicli by some geologists are said to have been produced by the 

 action of a diluvian wave, or deluge, sw-eeping over the surface of the earth."f 

 More recent opinions upon the presumed agencies which have brought together 

 the heterogenous materials forming the gravel and clay beds, and deposited and 

 spread them over their present sites, have led to the adoption of the term 

 " drift," as more significantly expressing the modern view^s held on their mode 

 of transport. The " drift," therefore, includes the series of beds of gravel, 

 sand, loam, and boulder-clay, or till, the latter being but a northern provincial 

 term for the former. 



My late friend, the highly mtelligent geologist, Joshua Trimmer, whose well 

 known intimate acquaintance with these superficial deposits, from an extended 

 examination, has given high authority to his remarks upon them, was the first 

 to adopt, if not to originate, their more defined division into " lower drift, till, 

 or boulder-clay," "upper drift," and "warp of the drift." J My respected 

 friend afterwards divided his lower drift — till, or boulder-clay — into an upper 

 and lower boulder-clay ; founding this division upon what he and others had 

 observed in the Suffolk cliffs, at and near to Gorleston, During the many 

 agreeable gossips that I had with my late friend, I heard his views in relation 

 to the above-mentioned divisions, and as frequently combated them, from not 

 having observed anything in West Norfolk to warrant them ; and since my 

 residence at Yarmouth, after having repeatedly examined the cliff from Gorton 

 to Gorleston, and other localities, I have seen nothing to shake my scepticism 

 upon the subject. Trimmer wrote thus: "It appears that in the Gorleston 

 cliffs there are two boulder-clays, separated by a mass of sand, which, on the 

 authority of Woodward, has hitherto passed for the ' crag,' a term which has 

 now become as indefinite as that of ' drift,' or ' drifts.' The lower boulder- 

 clay is the tailing off of that so well known for its blocks of Scandinavian 

 origin, and which extends over the north of Europe and into the eastern side of 

 England. The upper boulder-clay is characterized by an abundance of oolitic 

 detritus ;" and he proceeds to say that, " the former overlaps the latter, with a 

 mass of sand interposed." § 



It ap])ears from the perusal of this cited paper that there were anomalies in 

 the structures of the superficial beds " which had perplexed" Mr. Trimmer ; 

 it also appears that these perplexities were removed by meeting with (for 

 thus he wrote) "some boulders of gneiss on the beach; and though during a 

 rapid examination we found none actually embedded, Mr. Gunu assured me he 

 had seen them in the cliff." || Erom having repeatedly examined these cHfis, 

 and having also dug into the so-caUed lower boulder-clay, or till, without meet- 

 ing with a boulder of any kind in situ, I cannot assent to the existence of two 

 bouldcr-chivs — an ui)per and a lower. 



Bem-ath tli(> sand underlying the true boulder-clay a highly ferruginous loam, 

 stained in ])la('(-s black by deconiposed vegetable matter, exists. Into this bed 

 I du{^ to the de[)lh of about five feet, and a trench, three feet by two, without 

 meeting with anything but one portion of black flint, about the size of my open 

 hand, with its angles rounded, and pebbles and small angulai' fragments of 



* T^olinna^ "Dilmnmw. p. 2. 1S23. 



t Clossiwy in "The Principles of Geolosr:^^" 



t " On the (^colosy of Norfolk, &c." published in the Journal of the R oval AgTicultural 

 Sonoty of En.irland. vol. vii.. psirt 2. IS 17. 



§ " On tho Upper and T.,mv(m- Houlder-clay of the Gorleston CUffs." Quart. Journal of the 

 Gooloixtcal Society, vol. xiii. IS.37. 



II Op. cit. 



