spectacle is the second on the list of those which are the most venomous: the bite of it is followed by certain death, after an interval of generally not more than fifteen or seventeen minutes. On the Coromandel coast this sort of snake is very abundant, and there, as well as throughout India, is called a cobra capello, or hooded snake: its ordinary length is from three to four feet, and the prevailing colour of these reptiles is yellow, spotted with black; its form resembles that of other oriental snakes, with the exception of a pouch, which runs from the back of the head two or three inches down the back. This pocket is but little visible when the reptile creeps, or is in a state of tranquillity; but, as soon as it is moved by anger or by pleasure, this becomes inflated, and stretches on each side the head of the animal: it then presents a flat surface, on which a pair of black spectacles are stretched upon a dirty yellow ground. The head of the creature appears to issue horizontally from the upper part of this pouch. The quality which distinguishes this snake from all the other species, is its excessive fondness for music; and this passion, if such a term may be used, is stronger in it than even in the white snake: this is so incontestable, that when the place of his retreat is known, he is invariably caught by these means. The Indians, who gain a livelihood by exhibiting, are also those who take them; and, as the method which they employ for doing it is not generally known, the following scene, which took place at the house of the governor of Pondicherry, may be considered as interesting. During dinner a servant came to inform the family, that a large cobra capello had been seen entering the cellar: orders were given that a snake-catcher should be sent for, and every one repaired to the cellar when he arrived. After having examined the place, to be certain where the reptile was concealed, the Malabar squatted down upon his heels, and began to play upon an instrument, which in shape resembled a flageolet, but had something of the sharp sound of a bagpipe. Scarcely had a minute elapsed when a cobra capello, about three feet in length, crept from under a mat, and placed himself at a short distance from the man, raising and giving a sort of vibratory motion to the upper part of his body, and extending his pouch,—an evident sign of the pleasure which the animal felt.

When all present had sufficiently witnessed this proceeding, a sign was made to the Malabar, who, seizing the animal by the end of the tail, took him up with rapidity, and placed him in an empty basket. Before admitting him into the troop of dancers,-for one of them, he, as well as most of the cobra capellos that are taken, was destined to become, it was necessary to deprive him of the means of being mischievous. To do this, he was placed at liberty upon the ground, he was then provoked by being struck with a piece of red cloth, fastened at the end of a stick, until at last he sprang furiously upon the cloth, which was then shaken with so much violence that his teeth were at length pulled out. He was then taken again by the tail, and placed in the basket.

The baskets in which the snakes are kept, and of which the Indians generally carry six, are flat and round; and fastened like scales at each end of a piece of bamboo, which rests upon the shoulders of the bearer. When the person who keeps the reptiles exhibits them in public, he commences by ranging the baskets before him in a semicircle, and makes the snakes come out in succession. At the sound of the in

strument the animal becomes erect, resting with about one-third of his body upon the ground; his pouch is extended, and he keeps up a balancing motion, the original impulse to which was given by the knee of the person who plays the instrument. Before concluding the exhibition, it is customary to make the snake caress this instrument, which is done by keeping up the sound, and advancing the pipe towards the animal, who on his side rests his head upon a calabash, through which this pipe is passed. After this ceremony, the snakes are put into their baskets, and carried away. A hard-boiled egg is the nourishment which they daily receive.

FROM THE JOURNAL OF SCIENCE, &c.

On the best Method of Warming and Ventilating Houses and other Buildings. By Mr. CHARLES SYLVESTER.

The action of the sun's rays on the surface of the earth, and the consequent accumulation of sensible heat, is a most instructive lesson, for the best mode of applying artificial heat for warming buildings; and our best ideas of ventilation are derived from those mechanical changes in the atmosphere occasioned by the rarefaction of the air, from the heat it acquires in contact with the earth's surface. If the earth were perfectly transparent, or had a surface capable of perfect reflection, it would not be at all heated by the sun's rays; and our atmosphere, supposing it to exist under such circumstances, would be destitute of those changes which are daily evinced in an infinite variety of currents. If the substance of the earth were a much better conductor of heat, we should experience less extremes of heat and cold upon its surface. The summer-heat would be more rapidly absorbed by the earth, and the rigour of winter would be much diminished by the heat derived from the earth in the sun's absence. The nature of soils, as regards their conducting power, has doubtless a great influence in limiting the extremes of temperature in winter and summer. heat produced on any part of the earth's surface, will be the greatest where the rays of the sun are vertical, and the surface of such a nature as to receive the rays with the greatest facility, its substratum being, at the same time, the worst conductor of heat, The air immediately in contact with this surface becomes heated, and specifically lighter than its superstratum. This causes, in the first instance, two simultaneous currents: one perpendicularly upwards, and the other, a lateral one from all the surrounding parts towards the centre of the heated surface. After the ascending current has attained a certain altitude, it progressively assumes an oblique and ultimately a lateral direction, but in an inverse order to that of the lower stratum. By this beautiful provision of natural economy, the heated air of the torrid zone, and the chilling currents from the polar regions mutually contribute to the prevention of those extremes of heat and cold, which would otherwise be fatal to every class of animated beings.

The

To form some idea of the effect which would result from a vertical sun upon a good reflecting surface, such as a black soil, unattended by the currents of air above alluded to, we have only to observe the VOL. I. No. 1.-Museum.

L

heat generated in hot-houses; in which case the heated air is to a certain degree prevented from ascending, and consequently the lateral current from coming in. The heat produced by these means, therefore, will be greater in proportion to the blackness and lightness of the soil, to the tightness of the surrounding walls and windows, and the perpendicularity of the sun's rays. Hence we see the importance of our atmosphere independently of its agency in respiration. Without it, bodies would receive their heat on those parts only which are exposed to the direct rays, and would become unequally heated in the inverse ratio of their conducting power.

When bodies are immersed in a heated medium, such as in air or water, they receive their heat on every side ; and it has been found by

; experience, that this mode of applying heat is of particular importance in the economy of animals and vegetables.

Nothing can be more unphilosophical than the common mode of warming ordinary rooms by open grates. To put an extreme case of this mode of warming, we have only to instance the effect of making a fire in the open air. In this instance, there is free access for the ascent of the rarefied current, and the lateral current rushing towards the fire is felt on every side, supposing no natural breeze prevailed. The effect of this cold current is so conspicuous on the human body, that few unaccustomed to such exposure would escape some variety of those affections called colds.

Our common dwellings approach this extreme case in proportion to the size of the fire, the width of the chimney, and the access of cold air by the doors and windows. In every case, as much cold air must be admitted as will effect the combustion of the fuel, and supply the demands of respiration. The air which would be barely sufficient for these purposes, coming immediately from a cold atmosphere into rooms with grates even of the best construction, will ever be a barrier to that comfort which we ought to experience, and which by the aid of other means can be easily attained.

Notwithstanding the absolute necessity of admitting a certain portion of fresh air into every room, it is a common practice with builders to make doors and windows so tight as frequently to be the sple cause of a smoky chimney. To obviate this evil, some have let in a certain quantity of atmospheric air under or near to the fire grate. By this expedient; those sitting around the fire are not annoyed by the cold current, but an inconvenience arises from this contrivance, which more than counterbalances its benefits. The air entering the room so near the fire immediately supplies the current up the chimney without changing the air of the room. A crowded room, and the presence of a number of lights, would, under such an arrangement, soon render the air unfit to breathe. Hence will appear the necessity for two currents into a room. The inlet for fresh air should be in a situation not liable to annoy those sitting in the room; the outlet is generally provided for in the chimney, which is commonly sufficient for rooms of ordinary size, but is mostly too small for large public rooms.

It will be evident from what has been observed, that in order to render rooms comfortable and wholesome, two objects are required. The one, is to keep up an uniform and agreeable temperature; the other to provide for a change of the air sufficient to preserve that de

a

a

summer.

rooms.

gree of purity essential to health, and which persons under certain pulmonary affections can so nicely appreciate.

It is evident that the former of these objects can never be attained by radiant heat; and yet, an open fire, which scarcely affords any other than radiant heat, is so connected with our domestic habits that it will be very long before the open grate will be entirely set aside. Under these circumstances, it has been found most expedient to use the combined effect of radiant heat with a constant supply of fresh air, raised to an agreeable temperature in the winter; and which, in certain cases may be cooled during the excessive heat of

Great difficulties have been experienced in most of the means hitherto employed for warming air. In the first place, from what has been previously observed concerning the action of the solar rays on the earth, the air cannot be warmed by radiant heat passing through it; therefore we can only give heat to a transparent fluid by bringing its particles in contact with a heated surface, and, in proportion as elastic fluids are more expansible, they are heated with more difficulty.

There are a number of properties which a body should possess, to afford a surface proper for heating air intended to warm and ventilate

For the sake of economy it should be a good conductor of heat, in order that the radiant heat which it receives on one surface may be safely transmitted to the other. The surface to be heated should be clean, that is, free from any foreign matter, but not polished; and when the temperature can be limited, it should never, under any circumstances be allowed to exceed 300°, Metals appear to be the best substances for heating air. The temperature is limited to 300° because the animal and vegetable matter, which is found mechanically mixed with the air at all times, will be decomposed if the temperature be raised a little higher. When this decomposition takes place, as is very observable when the heated surface is red hot, certain elastic fluids and vapours are produced, which give to the air a peculiar odour, and a deleterious quality which never fails to affect the health of those who inhale it for a length of time. This oppressive sensation has been mostly felt in churches and other places where large iron stoves are used and are sometimes heated to redness. The peculiar odour accompanying it has been erroneously attributed to the iron; and on this account, earthen ware or stone has been employed to form the exterior surface of the stove. It will, however, be found that whatever be the material, if the temperature at all approaches a red heat, the same smell will be perceived; as it arises entirely from the decomposition of the matter which is in the air, and not from the heating body. This matter is very visible to the naked eye, in a sunbeam let into a dark room.

When earthen ware or stone has been employed for stoves, its inferior conducting power has seldom allowed the exterior surface to get sufficiently hot, to produce the effect on the air above alluded to. And hence it has been less objectionable as affecting the purity of the air.

It must however be admitted, that if the body used for heating the air, does not undergo any change, a metal from its being a good conductor must be preferred to any other substance. Silver or platina, if it were not for the expense, would set aside every prejudice. But

long experience has shown that iron possesses every essential property. The slightly oxydated surface which is common to all iron coming from the forge or the mould in casting, is well fitted for receiving radiant heat. And if its temperature be kept below a red heat, there does not appear to be any limit to its durability. The latter point, therefore, is put out of all doubt, since it is essential, that the iron shall not be heated to a degree capable of decomposing animal and vegetable matter, in order to preserve the purity of the air which is warmed in contact with its surface.

With a view to insure the above objects, it will be necessary to dispose of the heat as it is produced from the combustion of the fuel, in such a way, that an extensive surface of iron shall be heated uniformly without the risk of attaining a much higher temperature than 300°. This can be accomplished by making the fire of a size proportionate to the interior surface of an iron vessel, and it is found that radiant heat is much more efficacious than the heat produced by flame and conducting flues. Having heated the interior surface of an iron vessel it may be conceived that the exterior surface will quickly attain the same degree, and that whatever heat may be carried off from the exterior will be as quickly given from the interior, and instantly replaced by the radiant fire.

The next material object is the means of disposing of the heat from the exterior surface. If it be surrounded by an open space, and that be connected with a flue or tunnel of a certain height, supposing there to be no inlet at the bottom, or outlet at the top, the air will commence a circulation; that on the heated surface would ascend, and its place be as constantly supplied by the surrounding air. In this way two currents will be established; one ascending from the heated surface, and the other descending on the outside of the tunnel; and these currents will go on, as long as any difference of density exists in the air of the different parts of the surrounding space. If now an opening be made in the bottom of this tunnel and another at the top, an ascending current will be kept up; which will be as the difference of density between external air and that of the heated column, and as the square root of the height of the tunnel.

Let D be the density of the external air;

V

=

d, that in the tunnel, which will be inversely as the heat supplied. the velocity which a heavy body would acquire by falling through the height of the tunnel; and the velocity of the ascending air.

Then v=V X

D-d

D

v =

This equally applies to chimneys, d being