IIARJDWICKE'S SCIENCE-GOSSIP. 



where at which a great development of lignite might 

 be expected, the lignite-bearing strata being there 

 represented by pebble beds. 



Indeed, it seems to me that no theory based upon 

 the natural inferences of a geologist will explain the 

 existence of the popular tradition. Yet we should 

 certainly expect to find, as in the case of the Cum- 

 berland Lias, that it is by no means without an 

 apparent basis in facts, the errors in it arising from a 

 misinterpretation of the facts, not from a disregard for 

 them. And I have little doubt that the true explana- 

 tion of the tradition is to be found in the following 

 considerations. 



Long before the geology of the district was under- 

 stood, the attention of large numbers of persons must 

 have been drawn to the excavations made for various 

 purposes in the alluvium of the Thames in and near 

 London. These always reveal the existence of large 

 quantities of peat and drift-wood in the mud of the 

 marshes, and as the alluvium must have been dug 

 into from time to time, here and there, during many 

 centuries, wherever the construction of docks etc., 

 etc., made it necessary, the existence of a very con- 

 siderable thickness therein of more or less coal-like 

 material would be manifest. And not only does the 

 quantity of this material vastly exceed that visible 

 anywhere in the Woolwich beds, but excavations in 

 the marshes must have always been much more 

 numerous and the nature of the beds exposed much 

 better known than those of the other formation. 



Of course to the geologist of the present day, who 

 knows that the alluvium of the Thames marshes is 

 confined to the river valley, and that its thickness 

 seldom exceeds thirty to forty feet, the notion that 

 any persons once thought this peaty alluvium a 

 deposit of much greater thickness, not confined to 

 the Thames Valley, and with coal in its lower and 

 more consolidated beds, does not readily occur. But 

 the very difference of our stand-point, in this as in 

 other questions of folklore, is the chief hindrance to 

 onr understanding of the way in which the matter 

 would naturally present itself even to the intelligent 

 in the prescientific ages. It is, indeed, generally 

 recognised that the only way of obtaining insight into 

 the meaning of the customs, etc., of primitive man is 

 to learn in what way they are regarded by those who 

 observe them. And as regards the case before us, I 

 was fortunate enough to be able to look through a 

 paper sent to the secretary of a scientific society on 

 coal in south-eastern England, in which the writer 

 dwelt largely on the evidence of the drift-wood, etc., 

 of the Thames marshes, as an indication (if I 

 remember rightly) that coal was, in all probability, 

 to be met with lower down, in the more consolidated 

 beds. I could not get from the paper any definite 

 notions as to the writer's views with regard to the 

 relations between the Thames marsh deposits and 

 the Chalk, but it appeared to me that he did not look 

 on the alluvium as confined to the Thames Valley, 



but as having a much broader lateral extension. 

 And though he said nothing about Blackheath, it at 

 once occurred to me that this paper incidentally 

 threw much light on the way of looking at things 

 which had given Blackheath its popular reputation 

 as a probable coal-bearing locality. 



For if we grant, for the sake of argument, an 

 increased lateral extension to the alluvium of the 

 Thames Valley, both northward and southward, it 

 seems evident that under the high ground of the 

 plateau extending from Blackheath to Erith we might 

 fairly expect to find the southerly continuation ot 

 the marsh beds specially well preserved and con- 

 solidated. If, on the other hand, we look at the 

 Essex side of the river opposite, we see that on the 

 northern edge of the marshes there is a broad, low flat 

 of river gravel extending to a distance of four or five 

 miles from the Thames. But residents at Plaistow, 

 Barking, Ilford or Romford would know that beneath 

 this river gravel there was nothing but London clay, 

 as their well sections would plainly show. Residents 

 on the Blackheath-Erith plateau, on the other hand, 

 would get their water-supply from the lower part of 

 the Blackheath pebble beds, and never penetrate 

 deeply enough to ascertain whether the drift-wood 

 deposits existed beneath them at the level of the 

 river or not. And as beneath the gravel of London 

 there is London clay at a moderate depth, just as 

 beneath the gravel flat east of the river Lea, it would 

 be evident that if the drift-wood deposits of the 

 marshes, thickened, consolidated and coal-like, were 

 to be met with anywhere under the higher ground 

 bordering the Thames, the most likely spot was 

 decidedly the plateau between Erith and Blackheath. 



THE YELLOW ARCHANGEL (LAMIUM 

 GALEOBDOLON, CRANTZ). 



THIS plant, Lamium galeobdoloii or Galeobdolon 

 liitm m, Huds., the yellow archangel, is one of 

 the most interesting and representative of the British 

 Labiatai. The annexed description is from my note- 

 books, and may be useful and instructive to those 

 who might be unfamiliar with this beautiful "dead 

 nettle." 



Ordinal character, Labiata?. Usually hairy herbs, 

 with stoloniferous root-stocks, stems quadrilateral, 

 leaves opposite decussate, aromatic. Flowers ani- 

 somerous, in axillary whorls or verticillasters. Calyx 

 gamosepalous persistent inferior, 5-fid, often bilabiate. 

 Corolla gamopetalous, deciduous, irregular, labiate. 

 Stamens four, or less by imperfection or suppression, 

 didynamous, epipetalous, I anthers 2-celled. Ovary 

 deeply 4-lobed, 4-celled, or less by abortion. Style 

 slender, gymnobasic, stigma furcate, ovules solitary, 

 erect, anatropous, fruit constituting indehiscent 

 achisnia composed of the component lobes of the 

 ovary. 



