the engine-boilers, or pass through a steam-chest, or encircle the steam-pipe,-a constant renewal of the entire air between decks would go on. The current might be checked and regulated by valves, working in a very simple manner, before entering the chimney. In winter, the comfort of the passengers might be materially increased were the air warmed before being discharged into the cabins,―cold offensive currents would thus be avoided. It is singular that the same idea had occurred to Buchanan, when he wrote, in 1810, on heating by steam. "It is worthy of the consideration," he says, "of those acquainted with nautical affairs, how far it is applicable to ships, particularly to men-of-war." There is generally in steamers very little spare steam; but a very small portion would be requisite to warm the cabins; or hot water could be even more effectively employed. In this case, the external air, before entering the cabins, might pass through boxes or cases filled with iron or copper pipes heated with hot water or spare steam from the boiler; or the air itself might pass through the interstices of iron cases similarly heated, and then enter into the cabins through numerous small apertures. Thus warmth and the supply of fresh air

could in winter be combined.

I have alluded to the wind-fan having been made use of to supply fresh air or cool the furnace-room, the power being taken from the paddle-shaft. The fan admits of easy extension to the general ventilation of the steamer.*

In some recent instances, ventilators, on the principle of the Archimedian screw, have been tried for this purpose. Ventilators or revolving fans, on this plan which I have seen, are stated to have long been in use in factories. In an extensive flaxmill in Yorkshire, a very powerful fan on the principle of the screw propeller, driven by steam power, has been most suc-cessfully adopted, and the plan there in use for imparting mois

* In September 1842, a patent was granted to Robert Hazard, of Clifton, near Bristol, for improvements in ventilating carriages and cabins of steam-boats. He proposed to remove the vitiated air within a carriage by means of a fanner fixed at a convenient place, and set in motion by the revolution of the wheel, or by other motive power. He does not specify how he intended to apply his fans to cabins, but as regards the application to the latter, there is little scope for novelty.-Rep. Soc. of Arts, May 1843.

ture to the air, is highly deserving of general application, and ought never to be overlooked in ventilating arrangements.

The importance of keeping the furnace-room cool is of great consequence, especially in warm climates, as the heat is injurious to the health,-the cold air rushing to the furnace, falls like lead on the heads of the stokers. To remedy the over-heating, though it cannot prevent the draught, a plan, proposed by Mr Holdsworth of Dartmouth, has recently been tried in the Victoria and Albert, Royal Steam Packet, of having the bulkheads of two plates of sheet iron, and a stream of cold water kept constantly flowing between.

Another plan of ventilating, suitable for steam-ships, which the small space it occupies recommends, is the very ingenious method adopted by Mr Oldham at the Bank of England, of forcing in fresh air, by an air-condensing pump, through the interstices of iron cases heated by steam, the power being taken from the steam-engine, as described in the Civil Engineer's Journal, March 1839. This plan gives both fresh air and a modification of its temperature.

Mr Taylor's plan, described in the Transactions of the Society of Arts, London, 1810, of pumping out impure air from mines by an air-exhausting cylinder, likewise admits of application to steam-vessels. Mr Taylor's engine discharged more than 200 gallons of air per minute.* The idea of a motive power to work ventilators is of very old standing. A plan is given in the Phil. Trans. 1758, of using the fire-engines at mines for this purpose.† Various other suggestions might be made to apply ventilation to steam-ships—even the suction from the motion of the paddle-wheels might be made subservient to this purpose; but it is superfluous to say more on what admits of so many ways of attainment.

It is unquestionable, that the same share of attention has

* Mr Taylor's plan consisted in attaching a pump of simple construction to a small fall of water of about 12 feet. Steam-power could be substituted for water.

It was first proposed by Erasmus King, to have ventilators worked by the fire-engines of mines; and Mr Fitzgerald, in 1758 (see Phil. Trans.), suggested an improved method of doing so. I have alluded to the similarity of mine-ventilation with that of ships; thus, by having a series of flexible pipes connected with a wind-engine, or an air-pump attached to the steam-engine, immense supplies of air might be driven in, or drawn out, where required.

not been paid to the advancement of ventilation, as to other branches of the arts and sciences. A wide field is therefore open for improvements. But to be successful, these things must not be left to chance; they must form part of the construction of ships and steamers, and the naval architect and ventilator, as has been well observed by Dr Reid, "must work together."

While undue currents of cold air must be avoided-which are often troublesome, and must be injurious-ventilation, to be perfect, should be so arranged as to admit of being increased or diminished, according to the number of inmates. In our climate, in steamers, whether in coasting or long voyages, it would be of importance to have the power of raising the temperature of fresh air before admission to cabins; merely giving it, however, that slight degree of warmth that will not be injurious to its hygrometric condition. This would in

sure a larger volume of air being admitted. The plan is so easily attainable, that it might lead to the dispensing, in a great measure, with close arid stoves, so detrimental to the health in confined situations. It is remarked, that even Celsus, amongst the ancients, recommended large rooms for the sick, or a fire in the chimney to draw off bad air. Where fire-heat is made use of in cabins, it ought, if possible, to be in open fire grates. An ample exposition of the injurious effects of close stoves will be found in the Architectural Magazine, May 1838, p. 231, by Julius Jeffreys, Esq.

It is important for nautical men to know the great value of fire-heat as a purifier of the air of lower decks and close places, in the estimation of many of the most experienced navigators and naval commanders: Cooke and Nelson may be named.* How conspicuously the importance of sanatory regulations were illustrated in the remarkable voyage in 1773-75, of Captain Cook, who, during three years, out of 118 persons on board, lost four, and of these only one by sickness.† We have likewise several similar examples in the arctic and

An excellent paper on this subject, written nearly a century back, will be found in the Gent. Magazine, on the method of Preserving the Health of Seamen in long cruizes and voyages, where ventilation and fumigation are strongly nforced. Vol. xvii., 1747-8.

↑ Naval History 1773, p. 349.

antarctic voyages. See Expeditions of 1821, 1824, and later ones, where the advantages of warmth, combined with ventilation, are clearly shewn.

A very simple contrivance might be found useful for purifying lower decks when unoccupied : a grate, formed like a circular basket, hung in gimbals, which, like a pendulum, has its point of rest in the perpendicular.

The value of lime and vinegar washings and fumigations in destroying the bad effects of impure air, did not escape the older philosophers.* The knowledge of these facts was of vast utility in the days of Howard. Professor Daniel, and other chemists, have, in these times, recommended the use of chlorine gas and chloride of lime for a similar purpose. In combination with ventilating arrangements in ships, the value of such antidotes-especially where sickness prevails—should not be overlooked.

If we turn to the graphic pages of Smollett, we may at once perceive, by contrasting his description of a man-of-war with the inspection of one now-a-days, what great improvements have been made. But still, much is yet to be done in ship-ventilation generally throughout the world. The air, being invisible, deceives many a one, leading us to consider it pure, while it may be stagnant and corrupt; hence the necessity of impressing the admission of fresh air at all times, as we do light; and the absurd idea cannot be too soon exploded, of people enclosing themselves in an air-tight box or cabin. With improved means of ventilation of ships and steamers, the energies of all on board will be promoted. By in

* Dr Stephen Hales made many experiments recorded in his Statical Essays, London, 1731, vol. i, with a view to clear the air from noxious vapours. He found nothing so efficacious as a solution of potash. He says, page 207," Sal Tartar should be the best preservation against noxious vapours, as being a strong imbiber of sulphurous acid and watery vapour, as is also sea-salt." A solution of caustic alkali will take up fixed air as fast as it is produced.

The rapid absorption of ammonia by water, and the avidity of fresh lime for carbonic acid, point out the utility of water, with lime recently dissolved in it, for neutralizing the effects of impure air, either by the use of frequent fresh lime-washings, or exposing, in shallow vessels, frequently stirred, solutions of fresh lime. In factories, the sulphate of lime or gypsum is in general use for the absorption of ammonia, or removing the smell of the soil-pipes.

haling pure air during night as well as day, in cold or warm climates, increased longevity will be attained, and, at all events, the general comfort improved; and as Britain has outstripped most nations in the application of steam-power to useful purposes, why should she not take the lead in cultivating those arts which the physiologist has proved to be essential to the advancement of the physical condition of mankind?

Contributions towards Establishing the General Character of the Fossil Plants of the genus Sigillaria. By WILLIAM KING, Esq., Curator of the Museum of the Natural History Society of Northumberland, Durham, and Newcastle-uponTyne. With two Plates. (Communicated by the Author.) (Continued from page 21.)

A consideration of the ribs and furrows of Sigillaria will now engage our attention. From these characters, Lindley and Hutton appear to think, that the plants of this genus are allied to Cactidæ and Euphorbida. To these families, it is said, they seem to approach, particularly in their soft texture, in their deeply channelled stems, and especially in their scars being placed in perpendicular rows between the furrows.* Brongniart also refers to the resemblance between the external characters of the latter plants and those of Sigillaria. From what is stated when speaking of the internal structure of certain Cactuses, it may be inferred, that he supposes their ribs and furrows to be, in a measure, due to the same characters observable on the external surface of their ligneous cylinder. I mention this to ward off the notion that the ribs and furrows of Sigillaria arise from the same cause, judging from S. elegans, because in this species the ligneous cylinder has no appearance of being externally fluted.

Brongniart, in his general observations on Sigillaria, makes a slight allusion to the resemblance between the longitudinal ribs of S. Sillimani and S. contracta, and those of some arborescent ferns. Having had no opportunity of studying the latter, I have been compelled to examine more accessible plants, with the view of ascertaining if the like character occurs on any of their stems. Hitherto I have met with the most success among the Conifers. The surface of young shoots of the larch (Larix Europæa), and the spruce (Abies excelsa), are irregularly ribbed and

*"Fossil Flora," vol. i. p. 155.

+ "Archives du Musuem d'Histoire Naturelle," tome i. pp. 442, 443. 1839. + "Histoire des Vegetaux Fossiles," tome i. p. 403.