BRITISH ASSOCIATION MEETING. 



399 



use of iron was lmkllo^vll, made a long sojourn in tliis region ; and I am re- 

 minded of a large Indian mound \vhich I saw in St. Simond's Island in Georgia 

 — a mound ten acres in area, and having an average heiglit of live feet, chiefly 

 composed of cast-avray oyster-sheUs, throughout which arrow-heads, stone-axes, 

 and Indian pottery are dispersed. If the neighbouring river, the Alatamaha, 

 or the sea, which is at hand, shoidd invade, sweep away, and stratify the con- 

 tents of this mound, it might produce a very analogous accmnulation of human 

 implements, unmixed, perhaps, with human bones. Although the accompany- 

 ing sheUs are of living species, I believe the antiquity of the Abbeville and 

 Amiens flint-instruments to be great indeed if compared to the times of history 

 or tradition. I consider the gravel to be of fluviatile origin, but I could de- 

 tect nothing in the structure of its several parts indicating cataclysmal action ; 

 nothing that might not be due to such river-floods as we have witnessed in 

 Scotland during the last haK century. It must have requii'ed a long period for 

 the wearing down of the chalk which supplied the broken flints for the forma- 

 tion of so much gravel at various heights, sometimes one hundred feet above 

 the present level of the Somme ; for the deposition of fine sediment, including 

 entire shells, both terrestrial and aquatic ; and also for the denudation which the 

 entire mass of stratified drift has imdergone, portions having been swept away, 

 so that what remams of it often terminates abruptly in old river-cKffs, besides 

 being covered by a newer unstratified cbitt. To explain these changes I should 

 infer considerable oscillations in the level o^ the land in that part of Trance — 

 slow movements of upheaval and subsidence, deranging, but not wlioUy dis- 

 placing, the coiu'se of the ancient rivers. Lastly, the disappearance of the 

 elephant, rhinoceros, and other genera of cpiadrupeds now foreign to Europe, 

 implies, in like manner, a vast lapse of ages separating the era in which the 

 fossil implements were formed and that of the invasion of Gaul by the Romans. 

 Among the problems of high theoretical interest which the recent progress of 

 geology and natural history has brought i^ito notice, no one is more prominent, 

 and at the same time more obscure, than that relating to the origin of species. 

 On tills difficult and mysterious subject a work will very shortly appear by Mr. 

 Charles Darwin, the result of twenty years of observation and experiment in 

 zoology, botany, and geology, by which he has been led to the conclusion that 

 those powers of nature which give rise to races and permanent varieties in 

 animals and plants are the same as those which, in much longer periods, pro- 

 duce species, and, in a stiU longer series of ages, give rise to differences of 

 generic rank. He appears to me to have succeeded, by his investigations and 

 reasonings, to have thrown a flood of light on many classes of phenomena 

 connected with the afl&nities, geographical distribution, and geological succes- 

 sion of organic beings, for which no other hypothesis has been able, or has even 

 attempted to account. Among the communications sent into this section, I 

 have received from Dr. Dawson, of Montreal, one confirming the discovery 

 which he and I formerly announced, of a land-shell, or pupa, in the Coal-forma- 

 tion of Nova Scotia. When we contemplate the vast series of formations inter- 

 vening between the tertiary and carboniferous strata, all destitute of air- 

 breathing moUusca, at least of the terrestrial class, such a discovery affords an 

 important illustration of the extreme defectiveness of om geological records. 

 It has always appeared to me that the advocates of progressive development 

 have too much overlooked the imperfection of these records, and that conse- 

 quently a large part of the generalizations in which they have indulged in 

 regard to the first appearance of the different classes of animals, especially of 

 air-breathers, T\ill have to be modified or abandoned. Nevertheless, that the 

 doctrine of progressive development may contain in it the germs of a true 

 theory, I am far from denying. The consideration of this question will come 

 before you when the age of the white sandstone of Elgin is discussed — a rock 



