We have this week been much interested in inspecting an iron light-house just constructed by Messrs H and M D Grissell, and erected upon on their premises at the Regent's Canal Iron works, Hoxton. It is to be finally erected upon the island of Seskar, In the Gulf of Finland, some forty miles this side of Cronstadt. It was ordered some twelve months past by His Imperial Highness the Grand Duke Constantine, who is well known, takes great interest in all scientific pursuits. The tower is circular in form, and constructed of cast iron plates, one hundred in number, being ten in height and ten in circumference. The base of the tower is twenty feet in diameter.
The top under the gallery is twelve feet, whilst the height, being eighty-two feet, gives it the appearance of a column of good proportion. Round the top, on the outside of the column, is a gallery projecting three feet, supported by ornamental brackets, which bears the appearance of column cap. The plates forming the column vary in thickness from 1 ½ to 7/8 of an inch, and have strong internal flanges, which are made perfectly level and reduced to one uniform size under the planing machine. These plates are secured together by upwards of two thousand bolts and nuts of large size. In the centre of the tower is a large pipe eighteen inches in diameter, passing from the bottom to the top, which serves to assist in carrying the various iron floors, carries the dioptric light, and down which passes the weight of the light to revolve which produces the flashes.
There are five wrought iron floors carried upon wrought iron beams, supported by the internal flanges of the plates and centre column. These floors are reached from stage to stage by a neat wrought iron semi spiral staircase. The rooms are lighted by small plate glass windows, which are provided by a clever contrivance for keeping them shut or partially open to any angle, and so securely as to resist the force of the heaviest force of wind. On the summit of the column is placed the lantern, which is a twelve-sided figure, having a base of cast iron plates and surmounted with solid sashbars, framing thirty-six large panes of plate glass, each half an inch in thickness.
This is again surmounted by a galvanised wrought iron framed roof and covered by a fibrous slab which as justly gained so much celebrity at the new reading room, Britsh Museum, and in the ceiling of the new Convent Garden Theatre. This slab has the advantage of being fire proof, indestructible, and resisting excessive cold and heat. Upon the top of this slab covering is of copper, and underneath is a galvanised wrought iron ceiling. Upon the apex is mounted well-arranged cowl, surmounted again by an arrow forming a vane of no small dimensions. This cowl is a large hollow ball of copper open at the bottom, and into which passes the ventilating-chimney of the light. Upon the outer periphery on one side, and directly under the feather of the arrow, are pierced by many small square holes, forming, however, a less aperture than the diameter of the ball.
These holes always being under the feather are always sheltered from the wind; it follows that the wind in passing causes at the back of the ball a partial vacuum and into this the heated air from the lantern and light instantly passes, keeping the light-room nicely cool, and allowing of no down draught, thus preventing that flickering of the light so frequently seen in ill ventilated light rooms. The tower and lantern are painted bright red being the best distinguishing colour foe hazy and foggy weather. The internal portion of the lantern in daytime is hung with strong linen curtains to exclude the rays of the sun and this is very necessary. For when the sun's rays fall upon the foci of the lens of the rotatory portion of the light they form burning glasses of so much power that it would melt the brass of the lamp.
Underneath the glass windows on the inside of the lantern, is an ornamental gallery for the purpose of reaching all portions of the light, and enables the window and the light to be cleaned. The light is constructed according to the dioptric system of Freshnell, and was manufactured for Messrs; Grissell by Messrs Chance, at their glass works near Birmingham. By this system one single lamp placed in the focus of the apparatus suffices to throw a brilliant sheet of light in every direction of the horizon. This particular light belongs to the second order or size of the dioptric light, and what is termed a revolving light, with flashes every half a minute. The middle belt consists of twelve lenses, each of which comprises a series of concentric refracting rings, so as to have the effect of transmitting all the rays of light which fall upon it from the burner in pencil of parallel rays. So that the revolution of this belt of lenses will cause the appearance of a succession of flashes, the rate of this succession being a means of enabling the mariner to distinguish any particular revolving light.
Whatever rays from the lamp fall either above or below this system of lenses are intercepted by a series of horizontal circular prisms, of which thirteen are place and five below the lenses, each of them being formed as to reflect internally all light which enters it, and to cause all emerging rays to be parallel to each other and those which by transmitted by the lenses. This portion of the apparatus is designated technically as the "catadioptric" part from it's combining reflection with refraction in intercepting and transmitting the light; and it is necessary to observe that there is always a steady uniform light visible from this
Catadioptric portion, even during the interval of darkness of lenticular belt. The lamp which is used within the apparatus as a constant flow of oil, saturating and overflowing it's three concentric wicks by means of beautifully constructed internal pumps, moved by clock work; and there is a clever addition. Whereby the ceasing of the overflow and supply of oil puts in action an alarm to attract the notice of the attendant. The self acting rotatory machinery by which the lenses are made to revolve at the required rate is by a very nice piece of clock work, and performs it's work correctly, an does not seem likely to get out of order.
This article was transcribed from the Illustrated London News during Queen Victoria's visit to Aston Park March 6th 1858