SOME EVIDENTCES OF A GLACIAL EPOClI. 



Til 



snow, in sufficient quantities for 

 glacier building-. 



Tlie astronomical deductions made 

 bj^ Herschel, Arago, and latef by 

 Croll and others, have be^n of iaacl:i 

 value to geologists, by giving them 

 data- whicli shews that a much 

 lower temperature was proba'olo at the 

 time assigned for the Glacial Period. 

 This, at any rate, would be the case 

 in the northern hemisphere. Then 

 we have the suggestions that the 

 warm ocean currents were so deflected 

 from the countries whose climatic 

 ngors they now so much modify, that 

 a great change of temperatui-e 7.-oij]d 

 ensue. As an instance : — If the Gulf 

 Stream were to have its coursa turned, 

 say into the Pacific Ocean through an 

 opening in the Isthmus of Panama, 

 London would have a mean tempera- 

 ture about 40 degrees below the pre- 

 sent one. 



The prevalence of certain winds 

 might prove another passible factor; 

 though these would probably be the 

 result of a changed temperature, father 

 than the producer of it. 



I have, of course, only tr-uched upon 

 the possible causes which might aid 

 in bringing about the epoch of frigi- 

 ditj-; to attempt even to slietch out 

 the different theories, would need 

 much more time than I now have at 

 my disposal. 



The particular specimens brought to 

 illustrate the subject of this paper, 

 came from what is known as the 

 tipper Glacial Boulder Drift. They 

 were collected from that depcS"t during 

 the excavations made for a new rail- 

 way tunnel, which was being con- 

 structed in Bedfordshire, East Mid- 

 England. 



The organic remains, of which some 

 55 species were found, belong almost 

 entirely to the Mesozoic Period, and 

 consist of fossils derived principally 

 from the Lias, Oolitic and Cretaceous 

 Formations. These are in a much 

 more perfect condition than fossils of 

 the Drift usually are. Cephalopoda, 

 especially Ammonites, of which some 

 20 varieties were collected, were abun- 



ant. A piece of -wood Was founri 

 in good preservation; it was probably 

 a portion of some Pilocene Conifer. 

 One specimen of Trigonia Pulchella 

 was unearthed; this bivalve has only 

 before been found in the Urper Li :s 

 Clay near Lincoln, some 70 miles north 

 of the tunnel. Quite a heterogeneous 

 collection of rock fragments were gath- 

 ered, igneous, metamorphic, and sedi- 

 mentary, with numbers of septaria. 



Such a mass of debris has sufficient 

 internal evidence to show that it was 

 not laid down in the ordinary strati- 

 fied form; either by the action of 

 denudation, or by the aid of the re- 

 mains of a marine or a terrestrial 

 flora, or fauna, as is the case with the 

 rocks of the Laurentian age, leading 

 onward through all the Palaeozoic, 

 Mesozoic, and Tertiary periods, and 

 still upward to the immediate Pre- 

 glacial age, represented by such beds 

 as that of the Norfolk Forest deposit 

 of East Anglia. 



Some of the earliest geologists con- 

 sidered such accumulations to be the 

 result of ice action, in the form of 

 bergs. To this theory there are 

 weighty objections. These are the 

 two most important : — 



1st. There is no trace of stratification 

 in the deposit. 



2nd. There are no remains of the in- 

 habitants of the sea in which the ice 

 would float when it deposited its 

 gleanings, as all fossil remains belong 

 to clearly defined strata of a much 

 more ancient date; so much s:), that 

 we may speak of the Ice Age as be- 

 longing to yesterday, by comparison 

 with the deposits from which the 

 fossils were derived, which in that 

 case, might be spoken of as pre-his- 

 toric. The one exception, is the fossil 

 wood which was found, but this is 

 terrestrial, not marine. 



It seems from all the evidence that 

 can be adduced, that the vast accu- 

 mulations of clay, known as the Upper 

 Glacial Boulder Drift, must have been 

 deposited by the direct action of mov- 

 ing ice upon the land. Today the 

 same force may be seen at work in 



