P.S. You were so good as to notice a pamphlet of mine, in which I recommended the trial of an instrument for increasing the relative powers of the sun's and moon's attractions; and as I am now convinced that what I proposed is physically impossible, I shall be equally obliged if you will make this known to the public.

NEW MODE OF HEATING APARTMENTS.

SIR, Two well known qualities of air, are those of compression under mechanical powers, and expansion when exposed to the influence of heat; by this latter process its specific gravity becomes affected, that is, in equal bulks of hot air; and air at the common atmospherical temperature, the former was found to be the lightest. It is upon a knowledge of this property in air, to be affected by heat, that the warming of rooms is conducted, and it is only in those cases where this principle is not properly attended to, that apartments remain in a manner unbenefitted by the fires they possess? thus, it may happen that the setting of a grate too far back in the fire-place, proves detrimental to the warmth of the room, by carrying the greatest portion of heated air up the chimney flue. Under all circumstances however, the fire in the common grates, gives out a very partial heat to the room, and a very unnecessary quantity of warm air escapes along with the smoke.

The common fire-grate being in numerous instances preferable to stoves, it has been my study to render it still more serviceable in the heating of rooms, upon a plan cheaper than any before employed, and at the same time simple and not in the least interfering with the "setting up" of the grate, which alone, easy as it may appear, is yet matter of sufficient difficulty with many workmen. I have not only aimed at economy, but portability also, and I flatter myself, this warming apparatus, will be found in practice to be a useful and convenient addition to household furniture, from its being applicable to the grate of any fire-place, and possessing equal effect in all situations. In families this cheap and simple apparatus will be found peculiarly beneficial in the airing of chambers, damp rooms, cellars, &c., where, as ornament is not a matter of much consideration, those intended for such purposes only, may be made of the cheapest materials; but for the parlour or drawing-room, as a matter of course, a little more expense must be incurred to produce it in an elegant form.

When in use, it will be observed that this air heater, though comparatively small (for two might be hung on a bar eighteen inches long) has the power of distributing very hot air, which is attributable to the following cause; air, like all other imperfect conductors of caloric, only receives an impression of heat at the point of contact, that is, the heat does not spread itself rapidly through the whole body of air, but only by slow degrees, therefore I have divided the body of air, presented by this machine to the action of heat, into

strata, (if I may so express myself), of these there are three, (see the engraving) and the hottest alone is allowed to pass off into the apartment. The division from which this escapement takes place, is supplied with air from the remaining two, prepared with a degree of heat, derived from the waste heat of the metal, so that the whole apparatus has been contrived on true philosophical principles.

Having said thus much in its favour, it may be deemed superfluous to launch out into further details of its merits; under this impression I shall proceed to give some account of its construction.

London, June 18, 1829.

Reference to the Engraving.

H. D.

Fig. 1. A perspective view of the apparatus, the references to which apply also to the other figures. a, is one of the hooks for attaching it to the upper bar of a grate; b, a projection or hood, to convey the hot air into the apartment; c, an aperture for the admission of cool air; d, d, a curved slip of sheet iron, to prevent the smoke from being drawn into the room by the hood b, which it completely effects, even in a fire-place otherwise liable to smoke; e, a metal strap to receive the tongue g, Fig. 4. of the plateff, for lengthening the hood b, and carrying the hot air further into the

room.

Fig. 2. A section of the apparatus, showing the serpentine passage of the air in the divisions h h h; f, the situation for the plate Fig. 4, marked by dotted lines.

Fig. 3. A back view of the air-heater, a a a, three hooks, behind which is inserted the curved plate d. The middle hook should project about one inch, and the outside ones, about two inches, to suit a circular or a straight barred grate, as, for the former all the hooks will be engaged, but for the latter, only that in the middle will be serviceable.

Fig. 4. A plate, to be used when the draught of the fire-place affects the course of the current of hot air. It has merely its two outer edges turned square.

Fig. 5. The heater dissected; the dotted squares show where the trays ii, are to be hard soldered or rivetted, cccccc, three oblong openings for the admisssion of air, through which it takes the winding passage shown by the small darts.

The whole apparatus (except the curved plate d d) is best made of sheet copper or brass, and all the seams may be rivetted, provided they be afterwards luted with a little thick white or red lead paints. It may be also proper to notice here, that though the projection or hood is supposed to extend only one foot or one foot and a half from the fire-grate, it may with ease, be contrived of greater length to bring the hot air still further into a room.

H. D.

Transparent Astronomical Maps, designed by T. THOMAS, National Repository, and painted by W. I. SIMPSON, Newman Street.

THESE maps are four in number; the two first are planispheres, exhibiting the fixed stars termed the constellations, up to the fourth magnitude, in a very simple and beautiful manner; and having the earth in her path in the zodiac. These planispheres are divested of the ancient fabulous configurations commonly used in distinguishing the fixed stars, (as bear, dog, &c.) each cluster of which, or a constellation, being merely traced in a faint outline, thus enabling a superficial observer easily to learn and recognise the constellations as they appear in nature; an object of some moment when it is considered (as astronomers rationally believe) that the fixed stars are to other systems of planets what our sun is to this; that each has revolving around it planets similar to those in our system; and that many of these planets again have moons revolving around them, which perform the same duties towards their primary planets, which moons, or secondary planets, discharge in our system.

Mr. Thomas's third map is termed a tellurium, exhibiting the earth in the equinoctial and solstitial points in her orbit round the sun, representing the four seasons. To an observer on a given meridian, is illustrated a mid-day view of the earth in winter; a sunrise view in spring; a midnight view in summer; and a sunset in autumn. The phases of the moon are illustrated by placing her also in four parts of her orbit round the earth, viz.-in conjunction and opposition, and in her waxing and waning quadra

tures.

The fourth map is a representation of the planetary system, arranged in the usual way, viz.-the orbs mercury, venus, earth, mars, ceres, pallas, juno, vesta, jupiter, saturn, and georguim sidus, with their sattellites in their respective paths round the

sun.

These maps being upon rollers, and producing a very pleasing effect to the eye, besides being sufficiently transparent to admit the light, may be employed at pleasure as ornamental sun blinds to any apartment; they would thus be the means of forcing an acquaintance with astronomy upon every occupant of the rooms where they are placed; and would, notwithstanding the compulsion, be a very agreeable and easy mode of acquiring astronomical knowledge. To a library or study, Mr. Thomas's map blinds would form most appropriate and useful appendages; and it is due to the ingenious and intelligent inventor to add, that he has fully attained his object of combining ornament and utility in their adaptation.

VOL. V.-No. 83.

E

1ST JUNE, 1830.

Read's Syringe Valves.

AMONGST a variety of articles on one of the tables in the gallery we observed two of the "rose-heads" and valves belonging to one of the ingenious Mr. Read's syringes, as adapted to various purposes; these inventions, it must be confessed, are not very novel, but they are good, and as such ought not to be omitted in our work, where we desire to see every thing of merit, whether new or old, provided they be not too generally known. We had, however, another motive for bringing these little contrivances under the notice of our readers. Such information as we possess has led us to believe, that Mr. Read was the first person who improved the common shower syringe, by introducing a valve into the rose-head that would permit the water to flow rapidly into the cylinder, instead of through the minute holes, which valve would close from the pressure of the fluid during the discharge. By a reference to our account of new patents, in the present number, it will be seen, that syringes on precisely this principle, have been very recently patented by a Mr. Macdougall.

In Plate II, fig. a, represents one of these valves, which consists of a little metallic sphere placed loosely inside of the frustum of a cone, but prevented from falling through the largest end by a bar placed across the aperture.. This ball is of course forced against the bar on drawing in the water; and in discharging the water the ball is forced outwards, filling up the circular aperture, the liquid escaping in a fine shower through the perforations shewn. This cap a is screwed on to a syringe to be used for washing away the insects from fruit trees, and other horticultural purposes.

The other cap delineated marked 6, has two conical tubes, one with a ball, the other without; and is intended chiefly as a convenient domestic instrument for extinguishing fire. It receives its charge quickly through both holes, but is discharged only through one in a stream, the distance to which it is projected depending upon the degree of force applied to the piston rod.

VELOCITY OF SOUND.

THIS celebrated problem, which occasionally occupied the attention of the scientific world for the last 150 years, Newton, who first attempted the solution, found his result 170 feet per second short of the experimental velocity. Euler and other mathematicians, obtained similar results until the time of Laplace, who by the introduction of a new hypothesis, obtained results within 14 feet of the truth, as determined by experiment. But Mr. Herapath, with only the data of Newton, namely, the elastic force and specific gravity of the air, corrected by his own discoveries on the nature of airs, has produced a theorem which agrees with the mean of the best observations, to within 12 inches per second. In dry air, at the freezing point, he computes the velocity at 1089 4 feet per second; while the mean of the experi

ments, Captain Parry in the North, the French Academicians, Dr. Gregory, M. M. Arago, Dr. Moll and Goldingham, at Madras, gives 1089 3, when reduced to the same temperature.

66

Mr. Herapath has found too, that heat and sound are transmitted with equal velocity through the atmosphere; the rate of transmission increases or decreases with the temperature of the air, and decreases perpetually the higher we ascend; the heat diminishes uniformly at the rate of one degree Fah. for every 3261-8th feet of altitude, or 16 1-5th degrees Fah. for every mile; the total altitude of the air is, at a medium better than thirty miles," and the time sound would take to travel vertically through it, four minutes and 47 seconds. Besides these, the author draws some curious and unexpected consequences. He affirms, that the quantity of air has nothing to do with its total altitude, which would remain the same whether there was a half, a third, or a hundred times the quantity;" that an atmosphere of hydrogen would be 14 2-5ths times higher than ours is, that the greater the attraction of a body, in the same proportion the less is the altitude of its atmosphere, and vice versa. Hence he draws a physical proof of the phenomenon so often observed, but as yet unexplained by astronomers,-namely, the disproportionally small attraction of comets. He likewise notices and explains a very novel and curious paradox: for example, that the pressure of the air at the surface is uninfluenced by the velocity of sound, while, in the higher regions of the air, the pressure depends" on this very velocity."

For computing the diminution of Fahrenheit temperature for any elevation, the author gives the following rule:"Take a 1-100th of the altitude in yards; subtract a 1-10th of this from itself; and then add 2-10ths of the part 10 subtracted." The fall of temperature for an altitude of 7,600 yards is thus found to be 69.92, Fah.

STEAM ENGINE WITHOUT BOILER.

THE suggestion contained in the annexed letter from Mr. L. Gompertz may probably be well worthy the attention of those who can afford to devote the time, and incur the expense, of investigating by experiment, its feasibility and general economy. If really practicable, the advantages that would result are not overrated by our correspondent; whose well known scientific acquirements and mechanical ingenuity, must give weight to any proposition emanating from him. While we say this in justice to the writer, we must own, that we individually entertain but slight hopes of success. By a reference to our 4th vol. First Series, p. 66, it will be seen, that Mr. Thomas Howard generates the alcoholic and ethereal vapours in his engine, by a similar process to that suggested by Mr. Gompertz, and it would appear, by the