meria japonica, ditto. Laurels and Arbutus a little browned in the leaves, but apparently not otherwise damaged. Yellow Jasmine in full bloom. Fruit buds few in number, but sound when cut into.

Roses here have suffered severely in consequence of the young wood not being sufficiently ripened last autumn-Noisettes and Teas, and even hybrid Perpetuals, requiring to be cut close in.

I enclose a shoot of Deodar, a bit of Cryptomeria [apparently C. Lobbi], a twig of the old Hawthorn, yellow Jasmine, and one or two Primroses, as a sample of our vegetation at this season.

18. From Mr D. CUNNINGHAM, Palace Gardens, Fulham.
9th February 1860.

The thermometer, at 4 feet from the ground, on the 25th December 1860, stood at 7 degrees. Tea Roses, Euonymus, and young plants of Cedrus Deodara, have been killed. Laurus nobilis, Myrtles, Magnolias, and Pampas grass, have been very much injured; an old cork tree, and old Deodars, have also suffered; Araucarias, Cryptomeria, and Wellingtonia, are uninjured. None of the forest trees have suffered. But in Essex, Herts, and Derbyshire, where the thermometer reached zero, Ash, Yew, and other forest trees have been split.

15. Report from Mr PETER BOYs, Jardine Hall Garden,
Dumfriesshire, 5th March 1861.

Thermometer on morning of 24th December 1860, at 7 A.M., was five degrees below zero; the exposure being due north.

The following plants appear to be killed by the frost :-Cryptomeria japonica, Cupressus MNabiana, Taxodium sempervirens, Gynerium argenteum (Pampas grass), Weigela rosea, Abies Mertensiana (most of them killed), Brocoli, Greens, and Savoys.

The following are injured more or less severely:-Araucaria imbricata, branches below killed, upper ones browned, ends of branches drooping; Aucuba japonica, leaves and branches black; China Roses, Perpetual Roses, Erica stricta and herbacea, Dabacia polifolia, Bay and Portugal Laurels, Common Yew and Ivy, in exposed situations, have their leaves browned. Laurustinus and Arbutus have never thriven well at Jardine Hall. Plants of Cedrus Deodara have their leaves browned in some instances.

The following plants seem to be uninjured :-Pinus Jeffreyi, Abies Douglasii, A. cephalonica, A. Pattoniana, Picea grandis, P. Nordmanniana, Wellingtonia gigantea, Thuja gigantea, Cupressus Lawsoniana, Juniperus virginiana, J. macrocarpa, Cedrus Libani, Rhododendrons, Kalmias, Andromedas, Berberis, Ribes, Jasminum, Lonicera, Cotoncaster, Box and Holly, Salisburia

adiantifolia, Deutzia scabra, Forsythia viridissima, Spiræa Lindleyana, Paeonia Moutan, Ledum buxifolium, Hibiscus syriacus, Kerria japonica, Nuttallia cerasiformis, Aristolochia Sipho, Cydonia japonica, Mistleto, Tulip-tree, Magnolias, Chestnuts, Plum, Apricot and Peach, Raspberry, Strawberry, Asparagus.

The following is a list of plants, shrubs, and trees, more or less injured (so far as is yet known) by the frost, in the garden and pleasure-grounds at Culloden: Escallonia rubra, killed; Erica vagans, much injured; China Roses, Tea-scented and Bourbon, almost killed; Phillyreas, all nearly killed; Laurus nobilis (Sweet Bay), killed to the ground; Aucuba japonica, much injured; Arbutus Unedo, killed; Laurustinus killed to the ground; Common Laurel (Bay and Portugal) slightly touched in some places. Some Peach-trees slightly touched, but Apricots safe.

Roses, Auracarias, Aucubas, Escallonias, Leycesterias, and Common Laurels, are all killed down to where they were covered with snow. Portugal Laurels, Common Ivy, Privet, Cedrus Deodara, the last year's wood of Pears, Plums, and several sorts of Apples, very much destroyed.

On Azimuthal Condensing Apparatus of Unequal Power adapted for Fixed and Revolving Lighthouses placed on Islands near the Shore. By THOMAS STEVENSON, F.R.S.E., Civil Engineer.

In the volume of this Journal for 1855, I described different methods of distributing the rays proceeding from a flame equally over any required azimuthal angle. These devices are now applied to such fixed lights as are situated on the shores

of Sounds or narrow seas, where the power of the light ought to vary according to the varying width of the channel to be illuminated. In fixed lights, as formerly constructed, the portion of the light which was next the shore was either allowed to be wholly lost, from its showing in the landward direction, or it was returned through the focus by means of a sector of a spherical mirror, so as ultimately to strengthen a corresponding arc of the sea horizon. Cases, however, very frequently occur, in which it is desirable to employ this spare light, not in the direction exactly opposite to the dark arc, but in some other direction better suited to the configuration of the coast line. For example, at Isle Oronsay, in the narrow Sound of Skye —which was one of the first places where the condensing apparatus was adopted the light throughout nearly the whole of the illuminated arc does not require to be seen at a greater distance than three or four miles; while in one direction down the Sound, towards A B, it may be seen from a vessel's mast for about fifteen miles; and in another up the Sound, towards CD, it should be seen for about seven miles. By means of con

densing apparatus similar to that which was first described in this Journal, the spare light is condensed so as to increase the power up and down the Sound, and in this way one small lamp and an apparatus of small size are found sufficient for the purpose. The practical effect thus secured is, that a lamp consuming only about 210 gallons of oil annually produces a beam of rays (in the only direction in which great power is required) equal in effect to a first-class light consuming about 750 gallons. Condensing lights have now been established at Kyleak and Isle Oronsay, both in the Sound of Skye;

Phladda Island near Easdale, Runa Gall in the Sound of Mull, Corran Point in Loch Linnhe, and another is now being fitted up at MacArthur's Head, in the Sound of Islay. It has been computed, that the saving in first cost and consumption of oil, consequent on adopting this improvement at these six lighthouses, amounts, on the most moderate estimate, to about L.385 annually.

Since the first application of this principle of allocating the light to the different azimuthal arcs in the compound ratio due to their lengths of range, and the number of their degrees in azimuth, various improvements and extensions of the same principle have occurred to me; and I now, as a supplement to my first communication, add the following cases, both for revolving lights, and for fixed lights which require to show all round the horizon :

Revolving Lights of Unequal Range which do not Illuminate the

whole Horizon.

Revolving apparatus, where the whole horizon does not need to be illuminated, may, like the fixed apparatus, be similarly condensed. The power may be increased in the required directions in different ways, according to the size of the apparatus and the local requirements of the coast line. As, for example, at the Skervuile Rock, in the Sound of Jura, (where I first thought of applying the condensing principle to revolving lights), the method that seemed most suitable was to have the vertically straight prisms or mirrors for diverting the light into the required arc (vide vol. i. p. 273) fixed outside of the revolving apparatus. By this arrangement, whenever the revolving lenses passed out of the illuminated arc into the dark arc, the beams of rays emanating from them would be reflected by the series of prisms or mirrors, so as to pass over the arc that needed strengthening, which would thus be illuminated at the same instant by a direct and a reflected beam. The erection of a light on Skervuile was, however, delayed, and still remains in abeyance, and nothing was done regarding this plan of condensing. At MacArthur's Head, which was at one time (1859) intended to revolve, the apparatus was so large that the lantern would not admit of reflec

tors being fixed outside of the apparatus, as proposed for Skervuile, and the mirrors were therefore to have revolved along with the lenses, &c.* Attached to each mirror was a rod or standard, projecting downwards, with a roller on its lower end, which in its transit over the dark are passed up an inclined plane fixed to the trimming-path. In passing over the inclined plane the rollers would of course rise upwards, and raise the mirrors to the level of the lenses, so as to intercept the beam of light, and reflect it parallel to a beam from one of the other faces of the revolving apparatus, and thus direct it to the azimuth where additional strength was wanted. At the other extremity of the dark arc, the rollers were to be lowered by descending another inclined plane, and the mirrors descending with the rollers below the level of the lens, became again inoperative. After the drawings had been nearly completed, the character of the light was altered from a revolving to a fixed light, so that the plan has never yet been carried into practice. Other mechanical arrangements may, however, be found preferable in some cases.

Fixed Lights of Unequal Range, which Illuminate the whole

Horizon.

At fixed light stations, which require to show all round the horizon, but which are placed, for example, on an island very near the shore-it becomes desirable to allocate the power in proportion to the lengths of range in the different azimuths. The light should for those azimuths (which require to be more or less powerful than the rest) be collected into beams of parallel rays by sectors of holophotes proportionate in horizontal angle to the power required. There should then be placed in front concave divergers, straight vertically, and of such horizontal curvature as to spread the incident parallel rays over the required arcs. The light will thus be made to show all round the horizon, of power equal to a fixed light of the ordinary kind, in those azimuths where the ordinary fixed light apparatus is placed, and of different powers in the azi

My friend, Mr James Balfour, C.E., has lately suggested to me, that where the apparatus is of small size, one continuous mirror might be employed instead of a series of separate mirrors. This mirror should of course be a logarithmic spiral.

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