the refractive power of the water, be turned out of its straight course, and will fall two or three or more marks nearer the centre of the bason.

It is owing to the circumstance now stated, that an oar partly in and partly out of the water, appears broken; that objects appear distorted when seen through a crooked pane of glass; that a fish in the water appears much nearer the surface than it actually is; and that a skilful marksman, in shooting at it, must aim considerably below the place which it seems to occupy. It is owing to the refractive power of the atmosphere, that the sun is seen before he rises above the horizon in the morning, and after he sinks beneath it in the evening; that we sometimes see the moon, on her rising, totally eclipsed, while the sun is still seen in the opposite part of the horizon; and that the stars and planets are never seen in the places where they really are, except when they are in the zenith, or point directly over our head.

Many affecting and fatal accidents have happened, and are frequently recurring, particularly to children, and females in the higher ranks of life, from their clothes catching fire, most of which might be prevented, were the two following simple facts universally known and practically applied, that flame has a tendency to mount upwards; and that air is essentially requisite for supporting it. When the clothes of females take fire, as the fire generally begins at the lower parts of their dress, so long as they continue in an upright posture, the flames naturally ascending, and meeting with additional fuel as they rise, become more powerful in proportion; whereby the neck, the head, and other vital parts of the body are liable to be most injured; and, by running from

one part of the room to another, or from one apartment to another, as is most frequently the case, the air, which is the fuel of fire, gains free access to every part of their apparel, and feeds the increasing flame. In such cases, the sufferer should instantly throw her clothes over her head, and roll or lie upon them, in order to prevent the ascent of the flames and the access of fresh air. When this cannot conveniently be effected, she may still avoid great agony, and save her life, by throwing herself at full length on the floor, and rolling herself thereon. Though this method may not, in every case, completely extinguish the flame, it will to a certainty retard its progress, and prevent fatal injury to the vital parts. When assistance is at hand, the by-standers should immediately wrap a carpet, a hearth-rug, a great coat, or a blanket, around the head and body of the sufferer, who should be laid in a recumbent position, which will prove a certain preventive from danger. During the year 1813, the author noted down more than ten instances, recorded in the public prints, of females who were burnt to death by their clothes catching fire, all of which might have been prevented, had the simple expedients now stated been resorted to and promptly applied.

It may be remarked, in the next place, that many of the diseases to which mankind are subject-particularly fevers, small-pox, and other infectious disorders-might be prevented by the diffusion of knowledge in relation to their nature, their causes, and the means of prevention. It cannot have been overlooked, in the view of the intelligent observer, that fevers and other infectious disorders generally spread with the greatest facility and make the most dreadful havoc among the lower orders of

society. This is owing, in part, to the dirty state in which their houses are kept, every part of which affords proper materials for the production and detention of pestilential effluvia, and their ignoranee of the importance of pure atmospherical air to animal life, and the consequent necessity of daily ventilating their apartments. It is also owing in a great measure to the custom of persons crowding into the chambers of those who are labouring under such infectious diseases, and thereby not only increasing the strength of the infectious virus, but absorbing a portion of it in their own bodies, to spread its baleful influence in a wider circle. Such a conduct frequently proceeds from a want of conviction of the infectious nature of such disorders, and from ignorance of the rapid manner in which they are sometimes communicated from one to another, as well as from that obstinacy and from those inveterate prejudices which are always the accompaniments of ignorance. Though the cow-pox inoculation has been proved by experience to be an effectual preventive of that loathsome and often fatal disorder, the smallpox, yet numbers in the lower ranks of life cannot yet be persuaded to use this simple preventive, and will rather run the risk of experiencing all its disagreeable and dangerous effects both on their own persons and on those of their offspring. Their obstinate prejudices, in this and similar respects, are increased by their false views and reasonings respecting the doctrine of the Divine decrees, and the providence of the Almighty. They imagine, that to induce one species of disease for the prevention of another is attempting to take the government of the world out of the hands of the Creator, and that no means of preventing disorders can be of any avail,

if the Deity has otherwise decreed; not considering that the Almighty governs the world he has created by regular and invariable laws, and accomplishes his decrees through the intervention of those secondary causes, both natural and moral, which are continually operating in the physical and intellectual world. Were general knowledge more extensively diffused, and the minds of the multitude habituated to just principles and modes of reasoning, such fallacious views and opinions would be speedily dissipated, and consequently those physical evils and disorders which they produce would be in a great measure prevented.

Again, to ignorance we must likewise attribute, in a great measure, the pernicious effects of contaminated air in dwelling-houses. Pure air is as essentially requisite to the health and vigour of the animal system as wholesome food and drink. When contaminated by stagnation, by breathing, by fires or candles, it operates as a slow poison, and gradually undermines the human constitution; yet nothing is less attended to in the economy of health by the great majority of mankind. Because air is an invisible substance, and makes little impression on the organs of sense, they seem to act as if it had no existence. Hence we find, that no attention is paid by the lower orders of society to the proper ventilation of their apartments. In some cases, the windows of their houses are so fixed in the walls as to be incapable of being opened; and in other cases, where the windows are moveable, they are seldom opened, except by accident, for weeks and months together; and were it not that a door and a chimney are to be found in every habitable apartment, the air would be rendered in many instances absolutely unfit for respiration. Crowds of

tailors, weavers, shoemakers, and other mechanics, employed in sedentary occupations, are frequently pent up in close, and sometimes damp apartments, from morning till evening, without ever thinking of opening their windows for a single half hour for the admission of fresh air; and consequently, are continually breathing an atmosphere highly impregnated with the noxious gas emitted from the lungs, and the effluvia perspired from their bodies, which is most sensibly felt by its hot suffocating smell, when a person from the open air enters into such apartments. The sallow complexion of such persons plainly indicates the enervating effects produced by the air they breathe; and although its pernicious effects may not be sensibly felt, it gradually preys upon their constitutions, and often produces incurable asthmas, fevers, consumptions, and other dangerous disorders, which are frequently imputed to other causes. Nothing is more easy than to open the windows of an apartment, and other apertures that communicate with the external air, at meal hours, when the room is empty, in order to expel the contaminated air, and admit the pure vital fluid. No medicine or restorative is cheaper or of more importance to health and vigour than pure atmospherical air; yet, because it costs nothing, it is little regarded. Hints and admonitions in reference to this point are seldom attended to; for ignorance is always proud and obstinate, and the inconveniences supposed, in certain cases, to flow from the practice of ventilating particular apartments are seldom attempted to be remedied. It is, therefore, presumed, that were a knowledge of the nature of the atmosphere, of the ingredients that enter into its composition, of its indispensable necessity for the support and invigoration of animal life, of the circumstances by which it