232 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[July, 



air to the required place. These conduits may be made of zinc or 

 iron pipes; but a cheajier mode is to make wooden boxes of suffi- 

 cient size. To prevent the damp from affecting these, the outside 

 Kliould be covered with two or three coats of a composition of tar 

 and sand (three of the former to one of the latter). The best place, 

 in the (fenerality of churches, to lead the air to, is the passages; 

 and, indeed, in most other public buildings. The apertures at the 

 ])l.ice of ingress to the interior should be covered with cast-iron 

 gratings. But in order to diffuse the air as much as possible in its 

 passage through the gratings, along the under side of these, plates 

 of zinc, with small perforations, should be fixed, or sheets of hgrse- 

 hair cloth. For this purpose we would also recommend the adop- 

 tion of "cocoa-nut fibre matting" — it is very cheap, porous, and 

 can be made of any closeness of texture: it is becoming much used 

 for the passages and aisles of churches. If used in this way, any 

 species of grating, however rough, would do, as it would be hidden 

 by the cloth laid above it. One thing in connection with the 

 gratings should be borne in mind, that is, to have the apertures 

 greater, at least equal in surface to those on the outside. 



"The apertures for the admission of fresh air should be disposed 

 at equal distances round the building, if possible on all sides, so that, 

 from whatever quarter the wind blows, an aperture may be placed 

 BO as to receive its influence: not that the force of the wind 

 is necessary, for air, as we have shown, will find its way wherever 

 it is required, unless prevented; but in windy weather more air 

 v/ill he forced in, in a given time, than in calm weather. Having 

 |.rovided means for the admission of fresh, we will now direct 

 attention to the means for withdrawing the foul air. The aper- 

 tures for its escape should be placed in all cases at the highest part 

 of the ceiling. If the nature of the building will admit of it, the 

 area of the aperture should be distributed over the ceiling in more 

 tiiaii one place. Supposing the area of aperture of a church is 

 required to ba 3 square feet — if three apertures of 1 square foot 

 eacli, be placed along thereof at regular intervals, the building will 

 be more speedily ventilated than if one aperture of 3 feet square 

 was alone used," 



III the next chapter the author explains how ventilation may be 

 applied to dwelling-houses and shops, and describes several kinds 

 of ventilators which are applicable to the purpose — such as 

 fJailley's glass louvres, perforated glass, Dr. Arnott's valve, and 

 Mr. Toynbee's suspension valve, consisting of a square iron tube, 

 3 to 6 inches square, and 4 to 6 inches long, with a piece of per- 

 forated zinc over the external orifice, and at the back a piece of 

 oiled silk, which acts as a valve, so as to allow the warm and vitiated 

 air to pass up the chimney, and to prevent any smoke entering the 

 phamber. 



Mr. Burn describes a method of ventilating a house by the 

 staircase; It is simple, and appears to be very effective. 



"In supplying fresh air to the lobbies, halls, or central staircases 

 of large mansions, from which all the apartments are to be su])plied, 

 care should be taken to have the quantity sufficient in volume. It 

 will materially assist the ventilation if the air is warmed as it is 

 admitted. The air should be led to the floor of the hall, in which 

 apertures may be made to allow it to pass through; or it may be 

 Jtaken to the back of the skirting, or beneath permanently fixed 

 tables, the fronts of which should have plates of perforated zinc. 

 If the staircase is provided with a skylight, this should be kept 

 carefully closed; the desideratum, in such cases as we are now con- 

 sidering being to supply each apartment with means of withdrawing 

 the used air, so as to draw their supply of pure air from the central 

 magazine; not only ventilating themselves, but also the staircases, 

 passages, &c., these being supplied with fresh air from the central 

 magazine. If the skyli^rht was left open, thus creating a powerful 

 upward current, the flow of air into the apartments would be 

 materially retarded, if not in some cases altogether stopped. There 

 is one danger connected with this plan of supplying air to the 

 apartments of large mansions, worth being noticed'; this is if each 

 Bpartment is not properly ventilated, the foul air from it will ;)l)tain 

 access to the central magazine whenever the door is opened; its 

 egress through such being easier — the air in the central magazine 

 being thus contaminated, .^gain, some apartments may, from more 

 l>((werful ventilating arrangements, draw tlieir sup)ily j'roni another 

 apartment; this shows the necessity of ha\ing tlie sujqdy to the 

 central magazine ample. If the mansion consists of many stories, 

 each landing may be supplied with a separate supply of pure air, 

 independent of the openings in the hall jtreviously mentioned." 



In the next chapter, Mr. Hum explains how ventilation may be 

 applied to agricultural structures; and in the concluding cliapter. 

 ^various systems of warn\ing of buildings, construction of fire- 



places, and smoky chimneys. Here we must stop, before we are 

 tempted to make a few more extracts, as we have already intruded 

 farther than we at first intended upon the work. 



A Rnilimentarij Treatise on the History, Construction, and Illumina- 

 tion of Lighthouses. By Alan Stevenson, M. Inst. C.E.. Engineer 

 to the Board of Northern Lighthouses. London: M'eale. 1850. 

 It must certainly be esteemed a great recommendation for this 

 rudimentary treatise that it is written by the constructor of one of 

 the greatest lighthouses in the world — that at Skerryvore. .Mr. 

 Stevenson is the author of a description of this work, and therein 

 has laid the foundation of the present treatise, which applies to 

 lighthouses generally those principles which were discussed before 

 in especial reference to Skerryvore. Much space is given to the 

 various systems of illumination adopted; and of the remainder of 

 the book, although most valuable, it is so well known we are 

 almost deterred from making a quotation. At all risks, however, 

 we give some account of Skerryvore. 



"The Skerryvore Rocks, which lie about 12 miles w.s.w. of the 

 seaward point of the Isle of Tyree, in Argvllshire, were long 

 known as a terror to mariners, owing to the numerous shipwrecks, 

 fatal alike to the vessels and the crews, which had occurred in 

 their neighbourhood. A list, confessedly incomplete, enumerates 

 thirty vessels lost in the forty years preceding 181-i; but how 

 many others, which during that period had been reported as 

 "foundered at sea," or as to whose fate not even an opinion has 

 been hazarded, may have been wrecked on this dangerous reef, 

 which lies so much in the track of the shipping of Liverpool and 

 the Clyde, it would be vain to conjecture. The Commissioners of 

 the Northern Lighthouses had for many years entertained the 

 project of erecting a lighthouse on the 'Skerryvore; and with this 

 object had visited it, more especially in the year 18U, in company 

 with Sir M'alter Scott, who, in his diary, gives a graphic descrip- 

 tion of its inhospitable aspect. The great difficulty of landing on 

 the rock, which is worn smooth by the continual beat of Atlantic 

 waves which rise with undiminished power from the deep water 

 near it, held out no cheering prospect; and it was not until the 

 year 183t, when a minute survey of the reef was ordered by the 

 Board, that the idea of commencing this formidable work was 

 seriously embraced. 



" The reef is composed of numerous rocks, stretching over a 

 surface of nearly 8 miles from w.s.w. to e.n.e. The main nucleus, 

 which alone presents sufficient surface for the base of a lighthouse, 

 is nearly 3 miles from the seaward end of the cluster. It is com- 

 posed of a very compact gneiss, worn smooth as glass by the inces- 

 sant play of the waters, and is so. small that at high water little 

 remains around the base of the tower but a narrow band of a few 

 feet in width, aiul some rugged humps of rock, separated by gullies 

 through which the sea plays almost incessantly. The cutting of 

 the foundation for the tower in this irregular flinty mass occupied 

 nearly two summers; and the blasting of the rock in so narrow a 

 space, without any shelter from the risk of flying splinters, was 

 attended with much hazard. 



" In such a situation as that of Skerryvore everything was to be 

 provided beforehand and transported from a distance; and the 

 omission in the list of wants of e\en a little clay for the tamping 

 of the mine-holes, might for a time have entirely stopped the 

 works. Barracks were to be built at the workyard in the neigh- 

 bouring island of Tyree, and also in the Isle of Mull, where the 

 granite for the tower was quarried. Piers were also built in Mull 

 and Tyree for the shipment and landing of materials; and at the 

 latter place a harbour or basin, with a reservoir and sluices for 

 scouring the entrance, were formed for the accommodation of the 

 small vessel which attends the lighthouse. It was, besides, found 

 necessary, in order to expedite the transport of the building 

 materials from Tyree and Mull to Skerryvore Rock, to build a 

 steam-tug, which also served in the early stages of the work as a 

 floating barrack for the workmen. In that branch of the service 

 she ran many risks while she lay moored oft" the rock in a perilous 

 anchorage, with tiro-thinls of the horizon of foul ground, and a 

 rocky and deceitful bottom on which the anchor often tripped, 



" The operations at Skerryvore were commenced in the summer 

 of 1838, by placing on the rock a wooden barrack, similar to that 

 first used by ilr. Robert Stevenson at the Bell Rock. The frame- 

 work was erected in the cr)urse of the season on a part of the rock 

 as far removed as possible from the proposed foundation of the 

 liglithouse tower; but in tlie great gale which occurred on the 

 night of tjie 3rd of November following, it was entirely destroyed 



