require no ability at all. He should fairly invite a patient and candid hearing for them, point out the fallacy of their reasoning, the absurdity of their conclusions, and the dreadful consequences of a belief in them; for they require but a reading to be disproved-write them down in an honourable and manly mode of warfare, at once the contest of truth, the power of argument, and the cause of justice. This requires no feeble display of intellectual ability; but though the labour may be arduous and wearisome, TRUTH still remains the same; and though error may seem to usurp her place awhile, and obscure her brighter lustre, yet the penetrating and undaunted mind of man may explore the darkened regions, and lead her forth, seated on her snow-white throne, the unsullied goddess of the intellectual world.

In proceeding to consider the sacred duties of the PULPIT, I enter a wide field of discussion. Did I imagine that the ability requisite for the pulpit consists only in ready quotations from scripture, fluency of speech, inculcation of certain dogmas, or violent declamation against opposite parties; then would the task be easy, and sterling talent useless. Then might the presumptuous scribe of ignorance, or the ardent devotee of fanaticism, assert his undisputed claim to hold a place with those pre-eminent in learning and piety. The divine ought to possess not only wisdom, but the profoundest erudition. An acquaintance with the English language only, is not sufficient, but a knowledge of the original tongues is highly important, and indispensably necessary. Biblical understanding, and the ordinary talent to expound it, are but the two first steps to ascend the steep and craggy Another of the requisite qualificamountain. A critical study of the tions for the pulpit, is a well-grounded scriptures is a necessary qualification; acquaintance with the feelings and for without it, where is the fixed and passions of human nature. The diconscientious code of theological doc- vine should not consider his ministetrines which they are to promulgaterial labours at an end, when the disfor the benefit of others? Where is the treasury of argument which ought always to be in store, ready for discharge against the bold invaders of religion and of morals? Or how are they to teach, if they have not been taught?

He

course is concluded; but should go
round to the private houses of his
congregation, and diligently enforce
the practical lessons of the gospel,
his sole aim being to moralize the life,
and to fit the soul for eternal felicity,
adapting himself to the particular
capacities of each individual.
should be unwearied in his exertions
to carry the effect of his doctrines and
precepts to the hearts of his hearers,
never leaving his object till he reads
in the eyes of his congregation that
the desired impression is made. Force
of argument, bold and energetic lan-
guage, historical and descriptive illus-
tration, and eloquence of arrange-
ment, are so many means, which the
divine ought to possess, to reach the
hearts of his auditors. Whatever is
calculated to please, is adapted to
persuade; and eloquence is, perhaps,
a most efficient way of attaining
this purpose. Eloquence, which is
nature's proudest jewel, steals im-
perceptibly on the mind, and pro-
claims her power irresistible. No
profession affords so great a scope for
this invaluable talent as the pulpit—
no situation demands it more impera-
tively.

The divine has to encounter difficulties of every kind, and when he meets with foes, they are of the most formidable description. The adversaries he is opposed to in the discharge of his ministerial functions, are not merely professional ones, but personal, and generally rancorous enemies; and which require all the talent and energy of man to oppose and to baffle. Every thing that is levelled against the religion of God, it is his bounden duty to attack, and indefatigably pursue, till destruction shall have overtaken it. I do not say that the divine should attempt to crush by force all that he may consider hostile to the doctrines which he professes to inculcate; or, because he shall see the circulation of the productions of a Paine, or any other infidel writer, that he shall endeavour to destroy them without a hearing—without a trial-with- | out a reading? No! Much as I detest and abhor such unchristian and immoral principles, I would say, this would It is said of the celebrated Dr. be dastardly work indeed: this would | Chalmers, of Glasgow, that he seldom

space.

March, 18. 1822.

Your's, truly,
T. W

-m.

CHEMICAL ESSAYS, BY STUDIOSUS. (Continued from col. 350.)

Essay 4.-On the Composition of the Atmosphere, and on the Chemical and Physical Properties of Air.

leaves an idea till he completely ex- and runs through the confined world hausts it in language. This may ap- of time, to Heaven's unmeasured pear an useless mode of preaching; but I apprehend it is a most effectual one, when we consider the diversified classes of persons, and different degrees of understanding, which compose all religious congregations, inasmuch as such a method is pre-eminently calculated to strike all the auditors with pleasure and with conviction, though at various periods. The power and value of eloquence are incalculable. See a most striking exemplification of it in the case of Ligarius. Cicero had undertaken to plead his cause ; and Cæsar, well knowing the amazing effect of his splendid eloquence, resolutely determined, before leaving his apartments, that nothing whatever should save the life of Ligarius. But when Cicero began, his speech had such a variety of pathos, so irresistible a charm, that Cæsar's colour often changed, and his mind became torn by conflicting passions. At last he was so extremely affected, that his whole frame trembled, and he let drop some papers out of his hand;-thus subdued by the force of eloquence, he acquitted Ligarius. But to the point.

The duties of a divine are more awful, and more responsible, than those either of a barrister or a senator, and it is this responsibility which demands a greater proportion of talent, -a more enlarged expansion of intellect. He stands between earth and heaven, as the messenger of God and the herald of his people: he points the road to glory and immortality; he paints the gloomy horrors of the tomb; and leads his auditory to take a view, an appaling view, of the wide yawning gulph, anxious, as it were, to receive the deluded prey of the impious and profane. He has the guardianship of both soul and body entrusted to his care; the happiness and interest of their existence in this world, but, above all, their final and consummate destinies in the world to come. Faithfully to discharge the important duties imposed upon the divine, how vast, how superior, ought to be his ability. The barrister and the senator have to do only with mortality, but the divine has to do with immortality. The spheres of operation for the barrister and senator are bounded, but those of the divine are unbounded,

THE term atmosphere is derived from two Greek words, and signifies a body of vapour in a spherical form. By this term, we import the elastic, invisible, inodorous fluid, consisting of the air properly so called; together with the vapours, electric fluids, clouds, and unknown bodies, which are continually floating in it, inclosing the earth on every side, extending to an unknown height, and partaking of all its motions, annual and diurnal. It is the medium in which we live, and without which we could not exist.

The ancients were totally unacquainted with the properties and composition of the atmosphere, and the greater number of them considered the blue colour of the sky as essential to it, and never once thought of this being owing to the vapours which are continually mixing with it, and which have the property of reflecting the blue rays more copiously than any other, as first proved by the ingenious and immortal Saussure.

We are indebted to the celebrated Boyle for the discovery, that the atmosphere always contains two distinct substances, viz. air, which is a compound, consisting of Oxygen and Nitrogen Gases, and Water in a state of elastic vapour. Since his days, philosophers have proved beyond a doubt, that the atmosphere always contains a small proportion of Carbonic Acid Gas; and these we have every reason to suppose are the only substances that are essential to its constitution.

From what has been already advanced, it follows, that the atmosphere consists of the four following permanently elastic fluids, viz. Oxygen and Nitrogen Gases, which constitute the greatest and most important parts of the atmosphere; Carbonic Acid Gas; and

Water in a state of vapour:-Atmospheric Air. The ancients considered the air we breathe, as an element, or simple homogeneous fluid, and this opinion was universally maintained till about the end of the eighteenth century. We are indebted to the labours of Dr. Priestley, Sheele, and Lavoisier, for the discovery that air is a compound, consisting of Oxygen and Nitrogen Gases. We are not acquainted with any means by which to abstract the Nitrogen from its combination; Atmospheric Air, therefore, can only be analyzed by exposing it to the action of such bodies as will absorb its Oxygen Gas. The Nitrogen Gas will then remain behind, and the proportion of Oxygen Gas be ascertained, by the diminution of bulk; by which means we shall be enabled to determine the exact quantity of the two gases, in a given bulk of Atmospheric Air.

quantity of aeriform fluid, chiefly Nitrous Gas, which would alter the result. By this mode of analysis, I have always found 100 parts of Atmospheric Air to be composed of 22 parts of Oxygen Gas, and 78 parts Nitrogen Gas. This differs somewhat from the determination of Davy and others, who found the component parts of Atmospheric Air to be 21 Oxygen Gas, and 79 Nitrogen Gas.

From the experiments of a great number of philosophers, it is now proved beyond a doubt, that the different degrees of the salubrity of Atmospheric Air do not depend upon any difference in the quantities of its constituent parts as formerly supposed, for Atmospheric Air always contains exactly the same proportions of Oxygen and Nitrogen Gases, in all seasons, and in all situations, near the earth's surface, and at the greatest heights which the industry of man has been able to penetrate. Besides the two gases already mentioned, and which form the bulk of our atmo

The instruments employed for this purpose have received the name of Eudiometers; the first of which was constructed in consequence of the dis-sphere, it has been supposed to concovery of Dr. Priestley, that when tain a very small proportion of HydroAtmospheric Air is mixed with Nitro- gen Gas; and it has been proved very gen Gas over water, the bulk of the satisfactorily, that Carbonic Acid Gas mixture undergoes a very rapid dimi- always exists as a constituent part of nution, in consequence of the combi- air; and we are now well acquainted nation of the gas with the Oxygen of with the means by which to detect the the air, and the absorption of the presence of this gas, so that its exNitric Acid, thus formed by the wa-istence as a constituent part of Atmoter. This mode of analyzing Atmospheric Air being liable to many errors, has now fallen into disuse. Since the first construction of Dr. Priestley's Eudiometer, others have been proposed by De Marti, Berthollet, Humboldt, Sequin, Volta, &c.

The Eudiometer now in general use is one invented by the ingenious Mr. Davy, which, for simplicity, expedition, and accuracy, stands unrivalled. This consists of a small glass tube, divided into 100 equidistant parts. The tube is to be filled with Atmospheric Air, and immersed into a vessel, containing a concentrated solution of muriate or nitrate of iron in water, strongly impregnated with Nitrous Gas. The tube is to be moved a little backwards and forwards through the solution, to favour the absorption and condensation of the Oxygen Gas, which will be completed in a few minutes. The state of the greatest absorption must be marked, as the mixture always emits a

spheric Air is now proved beyond the least shadow of a doubt.

The proportion of Carbonic Acid Gas in air, was, till within a few years ago, estimated at 1 part in 100, but from the experiments of Mr. Dalton, it seems probable, that it does not amount to more than 1 in 1000. We are indebted to Dr. Black for the first step in the discovery of Carbonic Acid Gas as a constituent part of Atmospheric Air. As soon as the air of our atmosphere was known to be a compound body, it became an immediate object of inquiry, whether the gases which enter into its constitution are merely mechanically mixed together, or enter into chemical combination. With the exception of Sheele, philosophers seem to have considered the air as a mechanical mixture; but Bertholett, Davy, Humboldt, and other chemists, have demonstrated that it is a chemical compound, which opinion is now adopted by almost every chemist. Mr. Dalton, however,

has published an essay in the fifth called inspiration, and is always ravolume of the Manchester Memoirs, in ther longer than the latter, which is which he considers the general atmo-called expiration. The internal sursphere as composed principally of four particular gases, namely, Oxygen Gas, Nitrogen Gas, Carbonic Acid Gas, and Vapour; totally unconnected with each other, the particles of the one not acting on the particles of the other.

face of the lungs is lined with a transparent and delicate membrane, which, according to Haller, is not more than the thousandth part of an inch in thickness, but whose surface is said to be equal to the external surface of the whole body, that is, generally speaking, about 15 square feet. On this very fine and sensible membrane, a great number of blood vessels are distributed; and through these véssels, the whole mass of blood circu

Philosophers have long known, that the particles of elastic fluids repel each other with a force reciprocally proportional to the distance of their centres from each other. Now Mr. Dalton is of opinion, that this pro-lating within the body is successively perty only belongs to homogeneous elastic fluids, and that in a mixture of two or more elastic fluids, the particles of the one do not either attract or repel those of the others; and applying this property to the Atmospheric Air, he endeavours to prove by this very ingenious hypothesis, that the density and elastic force of each gas at the surface of the earth, are the effects of the weight of the atmosphere of that gas only, the different atmospheres not gravitating upon each other.

Chemists have started many objections against this very ingenious and beautiful hypothesis, which is indeed every thing but true. The absolute necessity of Atmospheric Air to respiration, is acknowledged by every body, and it is also well known, that no other gaseous body can be substituted for it. We have already demonstrated that the Atmospheric Air is composed of at least three gases, two of which are destructive to animal life; hence it follows, that only one of these gases is useful to respiration, this is the Oxygen Gas, to the presence of which we are warranted, both from the effects of respiration, and from the changes which blood undergoes when exposed to the influence of the atmosphere, to attribute all the changes observable in the colour of the blood.

Man, and indeed almost all animals, are provided with lungs to breathe through, and their lungs are lodged in the chest. They are also provided with a diaphragm, by which their respiration is performed. Respiration consists in the alternate taking in a certain quantity of air, the lungs expanding to receive it; and throwing it out again, the lungs contracting to expel it. The former of these is

propelled, and exposed through the medium of a thin pellicle, by far more delicate than the finest cambric, to the influence of the Atmospheric Air, with which the air-cells of the lungs have free communication, by means of the aspera arteria, trachea; or windpipe.

We find by experiment, that the quantity of Atmospheric Air respired, differs very much in different men, as also does the number of respirations in any given time. According to Dr. Kiell, by the rise of the sternum in man, and the descent of the diaphragm, room is afforded for 42 cubic inches of Atmospheric Air at every inspiration; and that a forced inspiration will give room for more than twice this quantity. In regard to the number of respirations in a minute, I myself make 18 at an average. I find that a young boy, upon whom I have made very frequent experiments, always breathes 22 times in a minute. Another boy upon whom I have also made experiments, only breathed 16 times. Dr. Hales reckons the number of respirations at 20 in a minute. Now, supposing that a man at an average breathes 20 times in a minute, he will make 1200 inspirations, and as many expirations, in an hour; consequently the number of respirations in the 24 hours will amount to 28,800. And again, if we admit that 42 cubic inches of air are received into the lungs at each inspiration, we shall see what a vast quantity of Atmospheric Air is respired in the 24 hours, amounting to no less than 1,209,600 cubic inches.

After the Atmospheric Air, inhaled by inspiration, has remained for a certain time in the pulmonary structure, it is again expelled, somewhat dimi