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the velocity of the water just above bridge, from many experiments, is not

greater than 24 feet per second.

Here b = 994; c = 820; v = 2; 4a = 64,3596.
Now 256

21850 21c 17220

= 1,443.

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Then 1,082 × 0,0786 = 0,084 feet, the fall sought. Which is about 1 inch; and is about half an inch more than the greatest fall observed by Mr. Labelye.

LXIV. Of the Earthquake in the West Parts of Cornwall, July 15, 1757. By the Rev. William Borlase, M. A., F. R. S. p. 499.

On Friday the 15th of July, 1757, a violent shock of an earthquake was felt in the western parts of Cornwall. The thermometer had been higher than usual, and the weather hot or calm, or both, for 8 days before; wind east and north-east. On the 14th in the morning, the wind shifting to the south-west, the weather calm and hazy, there was a shower. The afternoon hazy and fair, wind north-west. The barometer moderately high, but the mercury remarkably variable.

On the 15th in the morning, the wind fresh at north-west, the atmosphere hazy. Being on the sands, half a mile east of Penzance, at 10 A.M. near low water, Mr. B. perceived on the surface of the sands a very unusual inequality : for whereas there are seldom any unevennesses there, but what are made by the rippling of the water, he found the sands, for above 100 yards square, all full of little tubercles, each as large as a moderate mole-hill, and in the middle a black speck on the top, as if something had issued thence. Between these convexities were hollow basins of an equal diameter. From one of these hollows there issued a strong rush of water, about the thickness of a man's wrist, never observed there before nor since. About a quarter after 6, P.M. the sky dusky, the wind being at w.N.w., it fell quite calm. At half past 6, being then at Penzance, with some company, they were suddenly alarmed with a rumbling noise, as if a coach or waggon had passed near them over an uneven pavement; but the noise was as loud in the beginning and at the end as in the middle; which neither the sound of thunder or of carriages ever is. The sash-casements jarred: one gentleman thought his chair moved under him; and the gardener, then in the dwelling house (about 100 yards distant from them) felt the stone pavement of the room he was in move very sensibly.

The shock was not equally loud or violent. Its extent was from the isles of

Scilly eastward as far as Liskerd, and towards the north as far as Camelford. At Plymouth it was just sensible. In several places the houses shook, the windows rattled, the floors lifted, the chamber-bells rung, the pewter, &c. on the shelves were much agitated. Thus was this earthquake felt in towns, houses, and grounds adjacent; but still more particularly alarming in the mines, where there is less refuge, and consequently a greater dread from the tremors of the earth. In these it was heard and felt at all depths, to 70 fathoms or more, and seemed as below them.

LXV. On the Sleep of Plants; and of that Faculty which Linneus calls Vigili Florum; with an Enumeration of several Plants which are subject to that Law. By Mr. Richard Pulteney of Leicester. P. 506.

Acosta and Prosper Alpinus, who both wrote near the conclusion of the 16th century, appear to be the first who recorded that nocturnal change in the leaves of plants, which has since been called somnus. It is an observation indeed as old as Pliny's time, that the leaves of trefoil assume an erect situation on the coming of storms. The same is observable of our wood-sorrel; and Linneus adds, of almost all plants with declinated stamina. In the trifolium pratense album C. B. or common white-flowered meadow-trefoil, it is so obvious, that the common people in Sweden remark, and prognosticate the coming of tempests and rain from it.

The examples of sleeping plants instanced by Alpinus are but few. That author says, it was common to several Egyptian species; but specifies only the Acacia, Abrus, Absus, Sesban, and the tamarind-tree. Cornutus some time. afterwards remarked this property in the Pseudo-acacia Americana. From that time it has remained almost unnoticed, till Linneus, ever attentive to nature's works, discovered that the same affair was transacted in many other plants; and his observations have furnished us with numerous and obvious examples of it. Mr. Miller mentions it in the medicago arborea Linn. Sp. Pl. 778; and we may add to the list two other common plants not mentioned by Linneus: these are the phaseolus vulgaris, common kidney-bean; and the trifolium pratense purpureum majus, or clover-grass: in both which this nocturnal change is remarkably displayed. Doubtless the same property exists in numberless other species; and future observation will very probably confirm Dr. Hill's sentiment, that no plant or tree is wholly unaffected by it.

It is now more than 20 years since Linneus first attended to this quality in plants. In his Flora Lapponica, when speaking of the trifolium pratense album, as above-mentioned, he remarks, that the leaves of the mimosa, cassia, Bauhinia, Parkinsonia, Guilandina, and others in affinity with them, were subject to this change in the night-time: and he had then carried his observations so far, as to

find that heat and cold were not the cause of this quality; since they were alike influenced by it when placed in stoves, where the temperature of the air was always the same. The merit of reviving this subject is therefore due to the illustrious Swede; and the naturalist is greatly indebted to him for so far extending his observations on it.

The subject of the somnus plantarum cannot but be highly entertaining to the lovers of natural knowledge: and such, I apprehend, cannot be less entertained with that faculty which Linneus calls vigiliæ florum: of which we shall give a brief account.

Previous to our explanation of this affair it is proper to observe, that the flowers of most plants, after they are once opened, continue so night and day, until they drop off or die away. Several others, which shut in the night time, open in the morning either sooner or later, according to their respective situation in the sun or shade, or as they are influenced by the manifest changes of the atmosphere. There are however another class of flowers, which make the subject of these observations, which observe a more constant and uniform law in this particular. These open and shut duly and constantly at certain and determinate hours, exclusive of any manifest changes in the atmosphere; and this with so little variation in point of time, as to render the phenomenon well worth the observation of all whose taste leads them this way. This faculty in the flowers of plants is not altogether a new discovery; but we are indebted to the same hand for additional observations on this head also. It is so manifest in one of our common English plants, the tragopogon luteum, that our country-people long since called it John-go-to-bed-at-noon. Linneus's observations have extended to near 50 species, which are subject to this law. What we find principally on this subject, is in the Philosophia Botanica, p. 273. We will enumerate these plants, and mention the time when the flowers open and shut, that those who have opportunity and inclination may gratify themselves, and probably at the same time extend this branch of botanic knowledge still further.

It is proper to observe, that as these observations were made by Linneus in the academical garden at Upsal, whoever repeats them in this country will very probably find, that the difference of climate will occasion a variation in point of time: at least this will obtain in some species, as our own observations have taught us; in others the time has corresponded very exactly with the account he has given us. Whether this faculty has any connexion with the great article of fecundation in the economy of flowers, Mr. P. cannot determine: in the mean time it is not improbable. Future and repeated observations, and well-adapted experiments, will tend to illustrate this matter, and it may lead the way to a full explanation of the cause.

1. Anagallis flore phoeniceo c. в. pin. 252. Raii Syn. p. 282. Anagallis ar

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vensis Lin. Spec. plant. p. 148. The male pimpernel. The flowers of this plant open about 8 o'clock in the inorning, and never close till past noon. This plant is common in kitchen-gardens and in corn-fields; it flowers in June, and continues in flower 3 months.-2. The anagallis cærulea foliis binis ternisve ex adverso nascentibus C. B. pin. p. 252. Raii Hist. Plant. p. 1024. Anagallis monelli Sp. Plant. 148. Blue-flowered pimpernel with narrow leaves. The flowers of this plant observe nearly the same time in opening and shutting as the foregoing.-3. Convolvulus peregrinus cæruleus folio oblongo C. B. pin. 295. Convolvulus tricolor Sp. Plant. 158. Little blue convolvulus, or bind-weed. This opens its flowers between the hours of 5 and 6 in the morning, and shuts them in the afternoon.-4. Phalangium parvo flore ramosum C. B. pin. 29. Raii Hist. Pl. 1193. Branched spider-wort with a small flower. These open about 7 in the morning, and close between 3 and 4 afternoon.-5. Lilium rubrum asphodeli radice C. B. pin. 80. Hemerocallis fulvus Sp. Pl. 324. The day-lilly. The flowers open about 5 in the morning, and shut at 7 or 8 in the evening. -6. Plantago aquatica minor. Park. 1245. Raii Syn. 257. Alisma ranunculoides Sp. Pl. 343. Fl. Suec. 2, No 325. The lesser water-plantain, during its flowering time, only opens its flowers each day about noon.-7. Caryophyllus sylvestris prolifer C. B. pin. 209. Raii Syn. 337. Dianthus prolifer Sp. Pl. 410. Proliferous pink. The flowers expand about 8 in the morning, and close again about 1 afternoon.-8. Spergula purpurea J. B. iii. 722. Raii Syn. p. 351. Arenaria rubra. Sp. Pl. 423. Purple spurrey. These expand between 9 and 10 in the morning, and close between 2 and 3 afternoon. This little plant is common among the corn in sandy soils, and flowers in June.-9. Portulaca latifolia sativa C. B. pin. 288. Portulaca oleracea Sp. Pl. p. 445. Common purslain, opens its flowers about 9 or 10 in the morning, and closes them again in about an hour's time.-10. Ficoides Africana, folio plantaginis undulato micis argenteis adsperso Boerh. Ludg. i. p. 291. Mesembryanthemum chrystallinum Sp. pl. 480. Diamond Ficoides. The flowers of this plant open at 9 or 10, and close at 3 or 4 afternoon.-11. Ficoides Africana folio tereti in villos radiatos abeunte. Tourn. Mesembryanthemum barbatum Sp. Pl. 482. The flowers of this species expand at 7 or 8 in the morning, and close about 2 afternoon.—12. Ficoides folio tereti Neapolitana flore candido Herm. Ludg. 252. Kali crassulæ minoris foliis C. B. pin. 289. Mesembryanthemum nodiflorum Sp. Pl. 480. The flowers of this plant open at 10 or 11 in the morning, and close at 3 afternoon. 13. Mesembryanthemum folio linguiformi latiore Dillen. Hort. Elth. Mesembryanthemum linguiforme Sp. Pl. 488. Ficoides with a tongue-shaped leaf These open at 7 or 8 in the morning, and are closed about 3 afternoon.-14. Nymphæa alba J. B. iii. 770. Raii Syn. 368. Nymphæa alba Sp. Pl. 510Fl. Suec. 2. N° 470. White water lily. This plant grows in rivers, ponds,

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and ditches, and the flowers lie upon the surface of the water. At their time of expansion, which is about 7 in the morning, the stalk is erected, and the flowe more clevated above the surface. In this situation it continues till about 4 afternoon, when the flower sinks to the surface of the water, and closes again.-15. Papaver erraticum nudicaule flore flavo odorato Dillen. Hort. Elth. 302. Papaver nudicaule Sp. Pl. p. 507. Wild poppy with a naked stalk and a yellow sweet-smelling flower. The flower of this plant opens at 5 in the morning, and closes at 7 in the evening.-16. Alyssoides incanum, foliis sinuatis Tourn. Inst. 213. Alyssum sinuatum Sp. Pl. 651. Hoary madwort with sinuated leaves. The flowers of this plant expand between 6 and 8 in the morning, and close at 4 afternoon.-17. Abutilon repens alceæ foliis, flore helvolo Dillen. Hort. Elth. Malva Caroliniana Sp. Pl. 688. Creeping Indian mallow with leaves like vervain mallow, and a flesh-coloured flower. These open at 9 or 10 in the morning, and close 'at 1 afternoon.-18. Tragopogon luteum Ger. 595. Raij Syn. 171. Tragopogon pratense Sp. Pl. 789. Yellow goats beard, or go-to-bed at-noon. The latter of these names was given to this plant long since, on account of this remarkable property. The flowers open in general about 3 or 4 o'clock, and close again about 9 or 10 in the morning. These flowers will perform their vigiliæ, if set in a phial of water, within doors for several mornings successively; and they are sometimes observed to be quite closed, from their utmost state of expansion, in less than a quarter of an hour. It flowers in June.-19. Tragopogon gramineis foliis, hirsutis. C. B. pin. 275. Raii Hist. Plant. 253. Rose-coloured goats beard. These open between 5 and 6 in the morning, and close about 11. Tragopogon hybridum Sp. Plant. 789. -20. Tragopogon, calycibus corolla brevioribus inermibus, foliis lyrato-sinuatis. Hort. Ups. 244. Sp. Pl. 790. Hall. Hort. Gotting. 2. p. 419. The flowers of this plant open at 6 or 7 in the morning, and shut between the hours of 12 and 4 afternoon.-21. Sonchus Tingitanus papaveris folio. Tourn. Raii Suppl. 137. Scorzonera Tingitana Sp. pl. 791. African sowthistle with a poppy leaf. This plant opens its flowers between 4 and 6 in the morning, and closes them in about 3 hours.-22. Sonchus repens, multis hieracium majus J. B. ii. 1017. Raii Syn. 163. Sonchus arvensis Sp. Pl. 793. Tree sowthistle. These flowers expand about 6 or 7, and close between 11 and 12 in the forenoon. This is common in cornfields, and flowers in June, July, and August.-23. Sonchus lævis Ger. Raii Syn. 162. Sonchus oleraceus Sp. Pl. 794. Smooth or unprickly These open about 5 in the morning, and close again at 11 or 12.-24. Sonchus lævis laciniatus cæruleus C. B. pin. 124. Raii Hist. pl. 225. Sonchus alpinus Sp. Pl. 794. Blue-flowered mountain sowthistle. These open about 7, and close about noon.-25. Sonchus tricubitalis, folio uspidato Morr. pin. Raii Syn. 163. Sonchus asper arborescens C. B. pin.

sowthistle, hares lettuce.

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