stone in Grange Quarry, Burntisland. The species is not rare in many places. Three or four others are also met with around Edinburgh. As this communication refers only to Stur's paper, I do not particularise them.

VIII. Low Night Temperatures in Relation to Slight Inequalities of Surface.. By ALEXANDER BUCHAN, A.M. (Read 12th April 1877.)

In a valuable paper on the Temperature and Humidity of the Air at Different Heights, recently published in the "Transactions of the Royal Society of Sciences" at Upsal, Dr Hamberg gives an account of some interesting observations made by him with the view of defining with some exactness the influence of the inequalities of the earth's surface on the temperature of the air during night. The instruments of observation were a dry and a wet bulb thermometer, at a height of 3 inches above the surface, and a similar pair of thermometers at a height of 5 feet. The thermometers were fixed to little posts, and their bulbs. were protected from direct radiation.

Over ground the surface of which is uneven and covered with grass the temperature close to the surface is generally higher over those portions which rise above the rest. Thus over even a small elevation of from 1 to 3 feet the temperature is frequently 2° or more higher than the general level of the plot of ground. On the other hand, a trench or depression 1 or 2 feet below the general level is often 2° or more colder than what is observed on the borders of the depression and over the general level. At the bottom of a ditch 5 to 8 feet deep, and width double the depth, the temperature fell on one occasion 10°.8 lower than that on the margin of the ditch.

Open drains for field irrigation always indicated, when covered with grass, 2° to 5°4 greater cold than the margins. of the drains. But when the sides and bottom of the drains were composed of bare clay, the reverse held good.

A tree, a bush, a pond, or a stream raised the tempera⚫ture all round, or, to speak more correctly, arrested to a great extent the fall of the temperature. The temperature was sensibly higher over short than over long grass, in

accordance with what Glaisher showed many years ago; and it was sensibly higher over sand than over grass. At the height of 5 feet the temperature also varied with the inequalities of the surface, but not nearly to the same extent as at 3 inches from the ground.

On a meadow the temperature fell one night to 40°5 and 48° 9 at the surface and at a height of 5 feet respectively; on the summit of a hillock, 150 feet high, at the same heights, it fell to 50°.2 and 51°3; whereas in a trench on the top of a hillock it fell to 43°3 and 50°, and on another night to 39°-9 and 45°.5. On a steep equalsloping side of a hillock 100 feet high, the differences between the temperature at the top and the temperature observed all down the sides almost to the foot were comparatively slight, being only from 2° to 3°.5. But at those places where it sloped less the difference became greater; where it expanded out into a little plain, still greater; and where it formed a depression the greatest differences were noted, in some cases greater even than the differences between the very summit and base of the hillock. In all these cases, when long grass took the place of shorter grass, the temperature was observed to fall more rapidly. In the streets of the town the temperatures at 5 inches, 5 feet, and 200 feet, were at midnight 57°2, 57°4, and 57°-9; and at 0·30 A.M. 56°.8, 57°, and 57° 6 respectively.

The bearing of all this on horticulture is evident. To secure the best protection for tender plants in spring when a night's frost may be productive of a ruinous loss, a gently sloping surface should, if possible, be selected. But if there be no choice, and the plant-beds must be made on a level piece of ground, let the beds slope slightly from the centre line on both sides to the trenches which separate them. Let the trenches furthermore be kept free from grass, weeds, leaves, and other litter, which being bad conductors of heat, will only retain and store up the cold of radiation; and let care be taken that the earth of the trenches be not kept loose by raking, but be beaten or trodden into as firmly compacted a mass as possible, so that the heat of the soil may the more readily be conducted to the surface. to counteract the cold rapidly increasing there through the effects of nocturnal radiation.

TRANS. BOT. SOC. VOL. XIII.

D

shire.

IX. Notes on the Alpine Flora of Ben Nevis, InvernessBy JOHN SADLER, F.R.P.S. (Read 11th January 1877.)

[The plants marked by an asterisk are not recorded in Mr H. C. Watson's "Topographical Botany" for his division of "Westerness."]

The Scottish Alpine Botanical Club met at Fort William on the evening of 24th July 1876, and took up their quarters in the Chevalier Hotel. Next morning our party, in number thirteen, including Colin Cameron, the guide, started for the summit of Ben Nevis, Inverness-shire. The distance from the village to the summit by the usual way of ascent is about 5 miles. At the height of 1000 feet our course was southward along a stream, which issues from a small lake at 1840 feet above the sea, called Lochan Meall an t-Suidhe.

On our way we noted the ordinary vegetation met with on similar mountain slopes in Scotland, along with Rhynchospora alba, Polygonum viviparum, Plantago maritima, and other subalpine species. At the north end of the lake there was abundance of the alpine aquatic form of Carex vulgaris, and at a considerable distance from the shore Isoetes lacustris,* Subularia aquatica,* and Lobelia Dortmanna* were obtained by wading. On the north side. there are patches of beautiful strand composed of disintegrated granite and porphyry, with which the mountain abounds. We failed to find Arctostaphylos alpina, which has been reported as occurring in the neighbourhood of the lake. Leaving the lake we continued the ascent till we reached a point about 2700 feet, where there is a rocky ravine or gorge called Coire na h-Urchaire, through which a small stream runs. This stream has its source in the last spring met with before reaching the summit. It flows westwards, and has an abrupt and precipitous course. In the ascent from the loch to this point we gathered Saxifraga aizoides, S. hypnoides, Gnaphalium supinum, Alchemilla alpina, Silene maritima, S. acaulis, Luzula spicata, Poa alpina and Cryptogramme crispa. The ravine is only 200 or 300 feet in length, and is certainly the best botanising spot on this side of the mountain. Here we met with

Thalictrum alpinum, Sagina saxatilis,* Rhodiola rosea, Epilobium alsinifolium, E. alpinum, Armeria maritima, Cochlearia officinalis, Polypodium alpestre, beautiful specimens of Cerastium Smithii, and C. trigynum, the last being in great abundance near the upper part of the ravine, and for 200 feet above it. The most remarkable plant of all was a form of Saxifraga stellaris, which grew in large mossy-looking patches, resembling Montia fontana, the leaves being as small, the branches as delicate, and the flowers nearly as minute. Several Hepatice were also collected, including Jungermannia cochleariformis and two varieties of Scapania undulata. Between the upper end of the ravine and the spring, 3363 feet above the sea, we gathered fine specimens of Sibbaldia procumbens, Aira alpina, Ranunculus acris, alpine form; Veronica humifusa, Salix herbacea, Cerastium pubescens, and C. compactum, the last in considerable quantity and in fine flower. At a short distance above the spring, or about 3500 feet, Phanerogamic vegetation and soil almost wholly disappear, only lichens and a few mosses are seen on the large blocks of porphyry with which the upper part of the mountain is covered. At 3900 feet we reached the verge of the precipices immediately overlooking Coire na Ciste, where there is a cairn. From this we proceeded along the top of these precipices, which face north-east, and form the back of the mountain. All the corries were filled with snow. The summit was reached amidst sleet and rain, thick mist, and a fierce cold wind, which unfortunately prevented us from seeing one of the most extensive prospects in Scotland.

On a clear day are seen mountain ranges in all directions, intermingled with extensive water surfaces; the view ranges from the Moray Firth and the mountains. of Ross and Sutherland in the north and north-east to Ben Lomond and the island of Colonsay in the south and south-west, comprehending a distance of about 180 miles. The scene can scarcely be equalled, or at least surpassed, in the diversity of magnificence and striking objects, and in majesty and grandeur.

On looking beneath us, a few paces from the summit, we see the edge of a frightful precipice, which cannot be approached without caution, and from which the boldest

must shrink. The edge is wholly composed of loose fragments, which a little pressure is often sufficient to displace, when they roll down the precipice with a rushing noise and tremendous crash, The sound produced by the rattling of the stone, as it impinges successively on projecting points of the perpendicular rock, is reverberated among the surrounding cliffs, and thunders along the valley below. The effect on the ear is grand and impressive, and has occasioned the dangerous amusement of heaving stones from the top of the precipice into the dreadful abyss.

The summit of the mountain, which is 4406 feet above the sea, is crowned by a cairn about 6 feet high. Close by the cairn a single very small plant of the starry Saxifrage (Saxifraga stellaris) was picked, thus being the highest flowering plant in Britain. A few feet below the summit, and on the verge of the precipice, we met with Andreæa nivalis, in great cushion-like masses, a moss confined to the summits of a few of our highest mountains.

The next day (26th) we visited the precipices or snow corries" on the north-east side of Ben Nevis. Our course was along the Stone Burn, or, in Gaelic, Allt a Mhuilinn, which takes its rise in Coire Leas, a little to the south of the snow cofries. In the ascent we again observed many species common to similar moorish and subalpine situations in the North of Scotland. Several mosses and lichens were collected, including Mnium subglobosum, Dicranum falcatum, magnificent specimens of Sphagnum compactum, and Cladonia deformis. At about 2000 feet above the sea we noted in one or two spots abundance of Cornus suecica, in flower and fruit, along with Lycopodium alpinum, Empetrum nigrum, Rubus Chamomorus, and Hookeria lucens, a moss not usually found at such an elevation. On the northmost rocks, nearest, the point of ascent, little of interest was met with.

Proceeding southward, and climbing into all accessible places, we met with Vaccinium uliginosum, Thalictrum alpinum, Silene acaulis, Potentilla alpestris,* Saxifraga oppositifolia, S. nivalis,* Cherleria sedoides,* Salix reticulata,* Oxyria reniformis, Veronica humifusa, Silene maritima, Armeria maritima, and Carex atrata* sparingly. C. rigida was more plentiful, and very large, but most of the