Nov. 20, 1879] 



NATURE 



67 



large quantity of Romano-Brit sh pe'.tcry, but it was duS 

 with metal implements, probably of iron. 



There are two caves at Crayford within 3 feet 3 inches 

 of each other ; they are exposed in the side of a chalk- 

 pit connected with the brick-fields. One of them mea- 

 sured, from the surface to the chalk, about 18 feet ; thence 

 to the floor, 17 feet 6 inches. The floor was of flints, 

 about 6 inches thick, which had been taken up at one 

 part and piled in a heap on the other side of the cave ; 

 about a quarter of the area, an irregular oval of iS feet 

 diameter, had been so treated. From this floor rose an 

 obtuse cone of sandy clay 6 feet high, washed in very 

 slowly and evenly by the rain. In the cone were found 

 flint flakes, and one worked scraper with a rough core, 

 from which flakes had been chipped, but no pottery. 

 Above this, coarser soil and lumps of chalk, with several 

 sorts of broken pottery, very coarse, black, spongy pot, 

 scarcely baked, containing a large quantity of crushed 

 shells not calcined, and a few pieces of pot made with 

 coarsely-pounded chalk — all these either without ornament 

 or only finger-nail marked : then finer pot of Roman 

 moulds, and fine black ware, with a Samian plate. All 

 were accompanied by large quantities of the bones of 

 domestic and food animals for about a foot, then coarse 

 earth and bones to the surface. 



From about the period of the Roman deposit until now 

 we know the value, and it would not be excessive to date 

 the commencement of the deposit of mud and the 

 abandonment of the cave perhaps at half that period 

 earlier. 



On the walls of this cave there are no marks of the im- 

 plement by which it was excavated, and the conclusion is 

 that the blocks were prised out. 



The cave adjoining this fell in early and was soon 

 obliterated. 



Before knowing of these caves flint flakes and two 

 " pot boilers " were found on the surface. 



Clusters of these pits are either huddled into small 

 areas sometimes or are spread out into lines, and they are 

 frequent in spots which, from the supply of water, must 

 have been thickly wooded, and so difficult [of access, or 

 from the bleakness of the situation unlikely to be noticed. 



There is a cluster at Bexley of thirty-five in about three 

 and a half acres, and another of forty-four. 



Some pits which are mostly filled up now, in the woods, 

 are part of a system and are connected by banks and 

 ditches, and the same banks with earthworks which are 

 of a late stone age, and also with clusters of hut circles, 

 and there is great probability that they served two uses- 

 retreat and storage, and as pitfalls, as to the last with an 

 ingenious contrivance in one instance for driving animals 

 down a deep covered way, either past a pit or, by an 

 arrangement of a simple barrier, shunting them into it for 

 the use of the camp. F. C. Spurrell 



PROF. CEIKIE ON THE GEOLOGY OF THE 



FAR WEST 

 C\& Monday the 10th inst. Prof. Geikie reopened the 

 v class of geology in the University of Edinburgh by 

 giving an account of his recent exploration of the western 

 territories of North America. There was a large attend- 

 ance of students and others. 



The Professor, in the outset, reminded his students 

 that last session he pointed out the remarkable lessons to 

 be learned from the geology of the western regions of 

 North America, more particularly in reference to the 

 changes which had taken place on the surface of the 

 earth from ordinary atmospheric causes. It was with 

 special reference to those changes that he took a journey 

 to the West. Had geology begun in those western terri- 

 tories, instead of among the old broken, gnarled, and con- 

 torted rocks of Europe and the east of America, its 

 progress, at all events in some departments, would have 



been far more rapid than it had been. He had three 

 objects in the expedition:— (1) To study the effects of 

 atmospheric and river erosion upon the surface of the 

 land ; there being no region where these lessons could 

 be learned with more wonderful impressiveness than in 

 those great plateaux and table lands. (2) To mark the 

 relation which the structure of the rocks underneath 

 bore to the form of the surface. In this country and in 

 Europe generally one was continually brought face to 

 face with evidence of dislocations, protrusion of igneous 

 rocks, contortions, and other complicated forms of geo- 

 logical structure which, save to experts in the subject, 

 made it often difficult to realise how much of the present 

 irregularity of the surface should be attributed to unequal 

 waste by ordinary atmospheric causes, and how much to 

 thedirect effects of underground movements. The Western 

 States and Territories of North America over which the 

 strata, for thousands of square miles, retained their 

 original horizontally, presented remarkable facilities for 

 the investigation of this subject, and had already, in the 

 hands of King, Hayden, Powell, Dutton, and others, 

 furnished ample materials for satisfactory discussion. 

 (3) To watch with his own eyes some of the last phases 

 of volcanic action. He had been familiar with the 

 phenomena of active volcanic vents as displayed in Italy 

 and the Lipari Isles ; but he was anxious to see some of 

 those marvellous evidences of the gradual decay of a vast 

 volcanic area so well displayed in the famous region of the 

 Yellowstone. The Professor went on to give a brief ac- 

 count of his journey. He stated that he was accompanied 

 throughout by a former student of the class, Mr. Henry 

 Drummond, F.G.S., whose constant hearty co-operation 

 had been one main element in the success of the expedition. 

 His route first lay westwards by railway into Colorado. 

 In crossing the prairies towards the Rocky Mountains he 

 noted, in the few sections that occurred, soft grey creta- 

 ceous or tertiary clays and marls. Getting down at some 

 of the stations, and looking at the ant-hills and burrows of 

 the prairie dog, he found that the surface of the prairies 

 was veneered with a thin coating of a pinkish, fine- 

 grained sand, sometimes approaching to gravel, its colour 

 being due to the presence of a great many small pieces of 

 fresh felspar. It was clear that this mineral, as well as 

 the quartz and occasional fragments of topaz, which he 

 saw, did not belong to the strata on which they lay. In 

 going west, the grains of sand, getting coarser, assumed 

 the form of distinct pebbles, till, when he reached the 

 mountains, they became huge blocks and boulders, 

 evidently derived from the heights beyond. The cause 

 of this wide diffusion of sand and gravel over the 

 prairies was constantly present to his mind during the 

 rest of the journey, and he took occasion on returning 

 eastward to halt and make a more detailed examination 

 of the subject. 



The term "Rocky Mountains,'' he remarked, was a 

 singularly unfortunate designation, under which had been 

 included a great many independent and totally distinct 

 mountain ranges. On most maps of North America a 

 continuous line of lofty ridge was inserted down the axis 

 of the continent and marked " Rocky Mountains." But 

 no such ridge existed. The great plateau had been 

 wrinkled by innumerable meridional folds which, dying out, 

 were replaced by others. Some of these folds formed 

 notable ranges of mountains with wide basins or plateaux 

 between them. It was thus possible to cross the axis of 

 the continent without traversing any mountains, rocky or 

 otherwise. The line of the Union Pacific Railroad 

 followed one of these natural routes. At its highest point 

 (upwards of 8,000 feet), so little did the landscape suggest 

 the altitude, that it had been found desirable to erect there 

 a wooden placard with the title " Summit of the Rocky 

 Mountains." 



Crossing the Missouri River at Kansas City, and strik- 

 ing westwards to Denver, the Professor said he halted for 



