A. Bennett. A plant, not only new to Norfolk, but to Great Britain, which one of my daughters and myself-my daughter being the actual discoverer-had the pleasure of finding last July. It was growing in from four to ten feet of water, accompanied by Chara stelligera, polyacantha, aspera, &c.

It is widely distributed in Europe, occurring in Scandinavia to France, and Belgium to Russia, also in Asia; more sparingly in Africa, America, and Australasia.

It is an interesting addition to our Flora, because it is not a critical species, and there can be no question of its being indigenous. CAREX TRINERVIS, DEGLAND. Another addition to Norfolk, and also to Great Britain, yet one that might well have been expected; indeed, M. Crepin, in his interesting Notes sur quelques plantes rares, ou critiques de la Belgique,' expresses his surprise it had not been found on the English coasts. Its history may be told in a few words. Last December, accompanied by Mr. W. W. Reeves, I was spending an evening with Mr. H. G. Glasspoole (whom many of you know well), and looking over his duplicates, when I saw, among other Carices, four specimens of a Carex which I felt sure was trinervis, Deg. But they were young; and I sent one of the smaller specimens to M. Lloyd, of Nantes. His reply was: "I believe your specimen is trinervis, but it would be well to get more developed specimens." Since then I have carefully examined the largest specimen (kindly given me by Mr. Glasspoole), and compared it with the beautiful plates in Boott's Illustrations of the genus Carex,' and with a series of specimens from the West of France, and I have no doubt it is the plant of Degland.

Dr. Boott remarks: "Drejer (in his Symbolæ), allies this species to C. glauca and C. hispida; the affinity, I think, is with the last." Most authors rank it near C. vulgaris, or C. acuta. Other names for it are C. frisica, Koch, and C. acuta, var. nervosa, C. A. Meyer. It is strictly a West European plant, occurring on the sand-dunes of the coast of Schleswig, the East and West Friesian Islands, Holland, Belgium, West of France, and, rarely, in Portugal.

Mr. Glasspoole's specimens were gathered either in 1869 or 1870, but he does not recollect the exact locality; however, where it does occur, it usually grows in abundance, and he hopes to refind it this year (1884).

CAREX EXTENSA, GOOD. Still grows at Cley. July, 1883.

Mr. F. Hanbury. I have specimens gathered by Mr. G. Fitt in 1843, and by Mr. Priest in 1844, at Caistor, both of which I owe to the kindness of Mr. Glasspoole.

SCLEROCHLOA PROCUMBENS.

1877. A. Bennett.

Near the Fish Wharf, Yarmouth,

Banks of the Bure, near Yarmouth, with S. distans, 1883. A. Bennett.

Only one locality is given by the Rev. K. Trimmer in his Flora, i.e. "The Meals, Stiffkey."

CHARA ASPERA, WILLD. In profusion at Hickling Broad, covering acres of the bottom, to the exclusion of almost all other aquatic vegetation. I believe this to be the Pochard Grass mentioned by Mr. Southwell in the second edition of Lubbock's 'Fauna of Norfolk.'

Somerton Broad, 1883. H. Groves.

CHARA POLYACANTHA, A. BR. Sparingly at Acle, 1883. A. Bennett. Sparingly at Hickling Broad and Heigham Sounds.

Somerton Broad. Messrs. Hanbury and Holmes, 1883.

Both the two last additional species for this County.

CHARA HISPIDA, LIN.

CHARA FOETIDA, A. Br.
NITELLA OPACA, AG.

1}

Acle, 1883. A. Bennett.

CHARA STELLIGERA, BAUER. A third station for this species can now be recorded,--Somerton Broad," where it is plentiful on one side of the broad." July, 1883. Messrs. Hanbury and Holmes.

Norfolk is still the only county in which this plant has been gathered, but I should quite expect it in Suffolk.

FRANKENIA LEVIS. Is still abundant at Cley. July, 1883. Mr. and Mrs. F. Hanbury.

Not as occurring in Norfolk, but because so interesting a 'find,' I would name Corynephorus canesceus, P. de B. 'On the sandy warren near Lakenheath, Suffolk,' July, 1883. Messrs. King and Druce. A (present) inland station for a sand-dune species, and another link in the chain of evidence for the 'Breck lands.' It should be looked for between Thetford and Brandon, on the Norfolk side.

IX.

EARTHQUAKES AND SUBSIDENCES IN NORFOLK.

BY HORACE B. WOODWARD, F.G.S.

(Of the Geological Survey of England).

Read 25th March, 1884.

In the peaceful agricultural county of Norfolk our thoughts are not often directed to those grand and awful workings of Nature, elsewhere too well known in the form of volcanoes. Happily for us, and for mankind in general, the districts ravaged by volcanic action have remained very much the same during historic times. Nevertheless here and there the associated phenomena of earthquakes have unexpectedly and painfully aroused attention to the instability of the earth's crust, and led to the uncomfortable feeling that home on terra firma (in certain situations at any rate) may be no more secure than life on the ocean wave.

A study of the geological history of England clearly proves that our country has during several epochs in the past been affected by great volcanic eruptions. The fiery records are preserved more particularly in the hilly country that lies to the north and west; and they are to be deciphered from the old lava-flows and ash-beds, and the altering or metamorphism of neighbouring strata.

Long ages have elapsed since the last of these eruptions, but even in our own county some of the relics have been handed down to us. An old writer remarked, on account of the variety of its soils, that "all England may be carved out of Norfolk," and to a certain extent this has really taken place. For the boulder clays and gravels, so well shown in the cliff sections east of Weybourn, and scattered over the length and breadth of the county, contain fragments from nearly every British rock-formation, And among these we find boulders of granite, gneiss, mica-schist, basalt, and greenstone, that tell the tale of volcanic action in the distant past when their parent rocks were formed, altered, or erupted.*

*Some of the igneous and metamorphic rocks are probably of Scandinavian origin.

Earthquakes are, however, occasionally felt in England, even in Norfolk, and then we read of persons alarmed, or slumberers disturbed by the violent rattling of window-frames and pictures, the clatter of jugs and basins, the opening of doors, and the ringing of bells; while much serious damage may be done to old and decayed buildings.

Similar manifestations of disturbance are sometimes afforded to those who reside near a railway, or in a road along which much heavy traffic passes. The vibration of the house is felt, and this shaking due to the passage of heavy bodies on the earth's surface, is naturally not very unlike that which would be caused by the passage of the equivalent to a heavy body acting on the earth's crust from beneath.

Earthquakes are due to internal pressure, which acts either in a wave-like form, commencing feebly in one place, attaining a maximum force further on, and finally dying away, as if the energy were exhausted; or again, the pressure acts on a centre, the force dying away in ripples in continually widening circles.

Such earthquake waves are of a very varied nature. Those which make themselves known to us are no doubt, and fortunately so, of a comparatively mild form; but others are often sufficiently violent to rupture the earth's surface; and if they undulate beneath the sea-bottom, the waters are violently agitated, and may cause much destruction of life and property when the waves are forced over the land.

These phenomena are indeed catastrophic, and although this term has been much abused, there is a tendency now-a-days to admit, that while uniformity has prevailed in the laws regulating life and matter, yet catastrophic effects are ever and anon produced by agents governed by these same laws. Thus, as the Rev. O. Fisher has pointed out, any pressure affecting the earth's crust might accumulate enormously before the crust yielded, but when ruptured a sudden movement might take place.*

While earthquakes accompany and often precede volcanic eruptions, so they sometimes cease to occur when the outburst takes place; but it is remarkable that they are felt in our own country, and in other lands far away from active volcanoes. Hence, if due

* Quart. Journ. Geol. Soc. vol. xvii. p. 4.

to similar causes, the subterranean forces must in these instances exhaust themselves in producing the earthquakes without giving rise to volcanic eruption. Professor Judd remarks that "there can be no doubt that in the great majority of instances the forces originating earthquake vibrations and volcanic outbursts are the same, and independent lines of reasoning have conducted us to the conclusion that these forces operate at very moderate distances from the earth's surface."* The distances he mentions are from seven or eight to thirty miles.

While several distinct causes may help to originate volcanic action, the actual eruption is now mainly attributed to the escape of imprisoned watery vapour and gases. Still we have yet much to learn on this subject, for Professor A. H. Green says: "What it is that starts the wave we do not exactly know. But earthquakes always precede great volcanic eruptions, and in their case may be reasonably supposed to be produced by the jar occasioned when imprisoned steam rends asunder a rocky barrier that has held it in. It is therefore not unlikely that some similar action originates all earthquakes."+

Some earthquakes, however, may be simply due to shrinkage and fracture of the earth's crust, and of such disturbances we have abundant evidence in the joints, faults, and contortions seen in our rocks in many places, as on the Devonshire coast near Torquay and Clovelly; but not in Norfolk, for there the contortions in the Drift are due to glacial action.

The oxidation of metallic substances in the interior of the earth is also admitted to be a likely source of local disturbance.

The following is a list of all the earthquakes affecting Norfolk of which I have been able to obtain a record, the principal authorities being given below, or cited with the record :—

PRINCIPAL AUTHORITIES.

Rev. Francis Blomefield. 'An Essay towards a Topographical History of the County of Norfolk.' 5 vols. (vols. 3 to 5 by the Rev. C. Parkin). Folio. Fersfield and Lynn.

R. Mallet. The Earthquake Catalogue of the British Association, 1852-1858.' Reprinted 1858.

*Volcanoes' (1881), p. 344.

+ 'Physical Geology' (1882), p. 387.