3d. In a dense fog, to an observer at a distance of two miles, neither the gas-light of 108 jets nor the oil-light from a four-wick burner gives any indication, however slight, of its existence.

of steam sufli

the sun.

It has been observed by Professor Tyndall, in his experi- A slight cloud ments in Dublin, that a steam-cloud of even a few feet of cient to obscure thickness is sufficient to totally obscure the rays of the sun itself, and as either the four-wick oil-lamp or the 28-jet gaslight is sufficiently powerful to illuminate the horizon corresponding to the ordinary elevations of sea-coast lighthouses, i. e., at distances from eighteen to twenty nautical (twenty-one to twenty-three statute) miles in clear weather, it is evident that the increased intensity of sea-coast lights is desired for those intermediate states of the atmosphere between dense fog on the one hand and clear weather on the other.

the atmosphere for which the most powerful

sired.

are de

In these conditions of the air, including all the varieties Conditions of of haziness and "thick" weather, up to dense fog, (and also in snow-storms,) light-houses are most useful; for these the lights light-house engineers of Europe are striving to find the most powerful lights, and to meet this want the electric light (which I have described at South Foreland, and which I shall more clearly exhibit in an account of my visit to the light-houses at the mouth of the Seine) and the gas-light (such as I have described at Haisborough and afterward saw on the coast of Ireland) have been introduced within a few 'years.

tric and gas

creased when

While both these lights can be maintained at moderate Power of elec power in fair weather, they have this advantage: they can lights can be inbe increased almost without limit when it becomes hazy needed. and thick; this can be done without any increase in the size or cost of the lenticular apparatus, since the electric light requires a lens much smaller than that required for an oil-lamp, and as I shall illustrate farther on, 324 jets can be burned in Wigham's triform gas-light without increasing the size of the lenticular apparatus or the diameter of the flame beyond the maximum (108 jets) which I saw at Haisborough.

It is this power of being increased, (according to the conFlexibility of ditions of the weather, from 28 jets by steps of 20 at a time, the gas-light. till 324 jets the beam from which, even when uncondensed, is equal to more than the united beam from 6,000 candles can throw their rays in a solid beam through the lenticular apparatus,) which gives to the gas light of Mr. Wigham its great "flexibility," to adopt the term so hap pily used by Professor Tyndall when speaking of this light,

Economy in use of gas.

Absence of flexibility in oil. light.

Question of the relative penetrat

and I believe in this regard it is superior to the electric
light.

In the gas-light in clear weather only a sufficient quantity
of gas is used to carry the light distinctly to the horizon.
The large quantity required for "thick" weather remains
stored in the reservoir till wanted, and the expensive light
is burned only when needed, whereas in the electric light,
though the engine-power is doubled in "thick" weather, yet
the ordinary fair-weather expense of the engines is much
greater than the fair-weather cost of the gas light-houses;
and, further, the gradations of power to which the gas-
light is subject are much more varied than in the electric
light, and the former can be suited by intelligent keepers to
any state of the atmosphere.

Of course the oil-light which we use in the United States has no 66 flexibility" and burns the same in fair weather as in foul, in the twilight of the evening as in the darkness of the night. This is a fact of very great importance in this country, and particularly in high latitudes in Great Britain. In the long twilights of the last summer, while between the mouths of the Tyne and Tweed, I found no difficulty in reading on the deck of the Vestal at half past 10 o'clock, and indeed it could hardly have been said to be dark during the entire night. In these long twilights and in clear nights great economy can be attained in the use of illuminating power, which can be stored up, as it were, to be used only when the weather demands that it shall be put forth in all its strength.

It is to be observed in this connection that the relative ing powers of the penetrating powers of the oil, the electric and gas lights, yet deter have not yet been sufficiently tested at a distance and in all

different lights

not mined.

Illustration of

of London.

sorts of weather. This is a matter of great importance, and
should be made the subject of an exhaustive series of ex-
periments.

Almost any illuminant is good enough for fair weather,
but the light which will be finally adopted by all nations
will be that which will send its rays to the greatest distance
in storm and thick weather.

The gas referees of London, to whom the English Board the gas referees of Trade have referred the matter of light-house illumination by gas, very cleverly illustrate this desideratum as follows:

"Suppose the case of two regiments armed in the main with short-range rifles, but each comprising a body of marksmen twenty in number in one regiment, and forty in the other, armed with rifles of the longest range.

"At 1,200 yards the power of these regiments would be represented solely by the numbers of their long-range riflemen-the power of the one at that distance being double that of the other, although at close quarters their destroying-power would be equal.

"Every flame of gas or oil may be said to be a sheaf of rays of various lengths or penetrating power, so that two lights which are equal near to their source may become unequal when viewed from a distance; and an analogous effect to that of distance will be produced by mists and fog, obstacles with which it is most desirable that light-houses should be able successfully to contend."

THE NEWARP LIGHT-SHIP.

size.

Material

and

Lights.

This light-ship marks one of the sands which form a per- Position. fect labyrinth off the coast of Norfolk and Lincolnshire. It is built of wood, is registered as 212 tons builders' measurement, and has three masts carrying fixed lights; the fore and mizzen being 24, and the main-mast light 34 feet above the sea. It is anchored in 17 fathoms of water by an anchor weighing 45 cwt., having 210 fathoms of 13-inch chain, and carries besides, two bower-anchors of 20 and 14 cwt. respectively, with 150 fathoms of chain each.

Moorings.

pet.

The ship carries a Daboll fog-trumpet, which is sounded by Daboll trummeans of an Ericsson hot-air engine with an 18-inch cylinder, placed below the deck and near the bow of the vessel. Both the smoke-funnel and the trumpet are placed forward of the foremast. The latter, which is removable, is kept below deck when not in use; when sounding it revolves once a minute.

provided.

A Chinese gong is provided for use in case of accident to Chinese gong the trumpet or engine, and it was sounding when we left the vessel, but we ran out of its range at a very short distance; I thought it inferior to the bells used in our lightships.

ed.

The trumpet was also sounded after we left the vessel, Trumpetsoundand although I judged it to be pitched at too high a note, according to the conclusions arrived at in our American experiments, we heard it with remarkable distinctness. At a distance of two miles it sounded very loud and clear; at six miles the sound had sensibly decreased, but it was quite audible when the Vestal was under way, and it was not until we had gone eight miles that it ceased to be heard.

Heard at eight miles.

necessary on

There was no wind to interfere with the sound, but my Fog-signals experience on this occasion satisfied me that, for localities light-ships. where fogs are as prevalent as at the stations occupied by

S. Ex. 54--8

Arrangements of lights on the masts.

English lightships' crews.

Table of rates

of pay.

our light-ships off our northern coast and in Long Island Sound, powerful fog-signals, operated by steam or hot-air, would be extremely useful to the immense commerce depending on these vessels for safety.

In order to assist in determining at night the direction in which light-ships are riding at their anchors, the lights on the mizzens are placed at lower elevations than those on the main masts.

In the English service each light ship has the following crew: one master, one mate, three lamp-lighters, and six able seamen, one of whom may be a carpenter. No applicants under thirty-two years of age are admitted. The following table shows the uniform rates of pay in the service:

Table of The master furnishes the provisions per the following

tions.

Uniform.

ra

table:

Meat, 10 pounds per week each man.

Bread, 7 pounds per week each man.
Flour, 2 pounds per week each man.
Peas, 1 pint per week each man.
Potatoes, 7 pounds per week each man.
Suet,pound per week each man.
Tea, 2 ounces per week each man.
Sugar, pound per week each man.
Beer, 3 gallons per week each man.

When on shore 18. 7d. per day is allowed each man in lien of provisions.

The master and mate are furnished a regulation uniformsuit, and the crew a cap, one shirt, and one pair of trousers