neys, or a wall out-tops the chimney it is connected with. In this case no fireplace can be proof against puffs, though the pneumatic grate is said to be much freer from this influence even than others.

An apparatus of this description is in operation at a house of business belonging to its inventor, Mr. Jeffreys, No. 148, Regent-street, being one of the depots for the well-known instrument, the Respirator," also that gentleman's invention. It has been visited by the most eminent men of science in London, and has received their unqualified approval, as also that of men of taste in design, who consider the plan to have great capability for tasteful decorations, and elegance of form.

We have ourselves seen it, and examined it attentively, and as far as we can judge from a single inspection, the foregoing statements are fully borne out.

Description of Mr. Jeffrey's Fresh-air Pneumatic Grate.-Fig. 1, is a vertical section; fig. 2, (p. 419)a horizontal section or plan, and fig. 3, a front view. On the front page fig. 4 is a front elevation, and fig. 5 a plan. Fig. 6 (p. 419) is a side elevation, and fig. 7 another side section. A is a common house chimney. B B is the capacious space in the chimney in which common grates are set. CC, the large front opening partially closed by the brick work C C, into which is set the apparatus E E, F F, which consists of a box below E E nearly square, having flat tubes F FF, placed parallel, very near to each other, and upright, or nearly so, and passing through a partition of metal R R, above, so that the current which is making its exit at LL from the tubes denoted by the vertical arrows, fig. 1, is kept distinct from the current passing between the tubes into the chimney denoted by the oblique arrows. This apparatus is set in the chimney only so far, that the back of it, b b, is many inches in advance of the back of the chimney a a, figs. 1 and 2, the greater the distance, the better will be the effect. G G, figs. 1, 2 and 3, is a grate of any suitable form placed in front of the above apparatus supported by the iron rods I I, which slide in tubes or collars fixed in the box E E, so that the grate may be moved backwards or forwards by means of the screw H, turned in front by a winch. The use of this construction is

to allow air to pass up behind the grate between it, and the apparatus EE, FF, shown by the arrows 1, 1, 1; which air keeps the flaming current (arrows 2,2,2) from entering between the tubes too low down; the current above the summit of the flame is thus only allowed to enter between, and play against the tubes; and much more heat is thrown forwards into the room. O O, figs. 1 and 3 are two cheeks of marble, common stone, or metal, which prevent the ascending current from the fire from being blown sideways; and N N, figs. 1 and 3 is a frieze of similar materials forming a screen for turning any smoke that may rise so high into the fissures between the tubes F, F, F. Thus there is no upright passage into the chimney, and it will be perceived that the very back of the fire is several inches in front of the wall of the room, W W, figs. 1 and 2; and the space from the upper bar of the grate G to the frieze N, is even much more than in ordinary grates, causing the opening in front to be very capacious, while the grate also faces the room at the sides as much as in front. A grate placed in this position, unaccompanied with any parti cular provision, would send most of its smoke into the room, although the frieze N should be brought to within half the distance, at which it is here placed above the grate; and it has been supposed by persons not familiar with the moveinents of heated currents, that by placing in its way the large apparatus, occupying most of the passage towards the chimney, the tendency of the smoke to enter the room would be increased; whereas, by thus obstructing the greater part of the passage the opposite effect is produced, the whole of the smoke enters the chimney with a steadiness unequalled by the draught of any common fire if the apertures are vertical, and their summit R R, is above the level of the frieze N. Hence, by this construction most smokey chimneys may be effectually cured. Nearly the same effect would be produced by plates of metal placed parallel with the edges forward between the fire and the chimney; but by employing the tubular apparatus FF, in addition to the above important effect of enabling the fire to stand forward into the room, the tubes may be made to receive air from the box below EE, and to discharge it into the

2. The air is isolated by a tube extending from one station to another; one extremity of the tube is connected with a gas-holder or collapsing vessel, as a reservoir to compensate for any diminution or increase of volume arising from compression or from changes in the temperature of the air in the tube, and for supplying any casual loss by leakage. The other extremity of the tube terminates with a pressure index.

3. It will be evident to every one acquainted with the physical properties of atmospheric air, that if any certain degree of compression be produced and maintained in the reservoir, at one station, the same degree of compression will speedily extend to the opposite station, where it will become visible to an observer by means of the index.

4. Thus, with ten weights producing ten different degrees of compression, distinguished from each other numerically, and having the index at the opposite station, marked by corresponding figures, any telegraphic numbers may be transmitted, referring in the usual way to a code of signals, which may be adapted to various purposes and to any language. The only manipulation is that of placing a weight of the required figure upon the collapsing vessel at one station, and the same figure will be represented by the index at the opposite station.

5. In establishments where the telegraphic communications do not require the constant attendance of a person to observe them, and where periodical attendance is sufficient, the signals may be correctly registered on paper, by connecting with the air tube an instrument called a pressure register, also invented by Mr. Crosley, which has been successfully employed in large gas-light establishments upwards of fourteen years, for registering the variations of the pressure of gas in street mains. The same instrument produces also an increased range of the index scale, by which means the chance of errors from minute divisions is obviated.

6. There being now three different projects for improvements in telegraphic communications, viz.: the Electro-Magnetic, the Hydraulic, and the Pneumatic Telegraphs, and assuming that such improvements are of importance to the state, as well as to railway proprietors and the community at large, it seems desirable that their merits should be

thoroughly investigated by competent engineers, and that the aid of government should be solicited, for the purpose of establishing, on a practical scale, the most eligible project.

7. It may be observed, that the introduction of railways, has not only created an additional use for telegraphic communications, but the important difficulty which previously existed in the expense of providing a proper line and safe foundation is, at once, removed by the side of the railway itself, possessing as it does, by its police, the most ample security against injury, either to the tubes or electric wires.

8. The prominent questions for consideration seem to be-the certainty and accuracy of the communications, the first cost, the expense of repair and superintendence, also the time required for transmitting intelligence.

9. On the question of time, it is quite clear that neither the hydraulic nor the pneumatic can compete with the electromagnetic telegraph in rapidity. No doubt, on investigation, each project will be found to possess its peculiar advantages. Thus, in considering the advantage one may have in point of time, another may possess a greater degree of certainty or accuracy in the communications, sufficient to outweigh the difference of time, for instance, between 1 second and 1 minute, or even between 1 second aud 5 or 10 minutes.

10. The projector of the Pneumatic Telegraph is not in possession of any experimental results on a practical scale by the electro-magnetic or by the hydraulic telegraphs, employed at any considerably extended distances, or of their continued operation for any long period of time; nor can he offer much decisive information, of a practical nature, analogous to the operation of the pneumatic telegraph on these points; the following circumstances may, however, be referred to:

11. There has been upwards of twenty years' experience in the transmission of gas for illumination through conduit pipes of various dimensions. In several instances, the gas has been supplied at the distances of five to eight miles by low degrees of pressure. As one proof of great rapidity of motion, it has been observed, that when any sudden interruption in the supply has occurred at the works, the extinction of all the lights,

the New River Company had discovered that immense waste took place, and that the water was appropriated in many extraordinary ways. He mentioned one instance where a smoke-jack having been found inefficient, a water wheel was formed in the chimney, and the meat roasted by its hydraulic power! My own observations lead me to believe, that in those districts where the supply of water is tolerably abundant, the quantity positively and absolutely wasted, far exceeds the quantity that is fairly used. In the districts of some of the southern companies, the period of supply is limited to one hour three times per week, and in these districts nearly one-third of the consumers are without the ordinary means for shutting off the water when their butts, &c. are filled-consequently the superfluous water runs to waste, to the great annoyance of those, whose cisterns being on a higher level seldom receive more than a very scanty supply. Persons sometimes quarrel with their water-rate, and dispense with the public supply. They sink a well on their premises-erect a pump-and obtain any quantity of water they please (as they say) for nothing. Taking the cost of the pump, the expense of sinking the well, and to these add the charge for labour in pumping (which is in exact proportion to the quantity raised) and I question whether there is in any case much saving. There is some little convenience in being able to obtain upon any particular occasion an extra quantity of water-but against this must be set the risk of being left at some seasons of the year, without any water at all. Calculated as the present water-charges are, to cover the enormous waste of the extravagant, they may perhaps seem high, although in many places, a like supply on similar terms, would be hailed with the utmost delight.

I believe whenever it shall become feasible for the water-companies to charge for the quantity actually consumed, the cost will be found extremely moderate, and quite as low, if not cheaper, than the expense incurred by individuals for private supplies.

Many persons would gladly pay for an increased supply of water, who, under the present arrangements cannot possibly obtain it; while those whose consumption was small, would reap the full benefit of their economy, and find their

charges proportionally diminished. Under such a system, the mains and services would always remain charged, and every cistern remain filled. The permanent and plentiful supply of water thus afforded, in the event of fire, would prove of incalculable advantage. It was well observed by Mr. Braidwood upon the investigation before alluded to, that "had the supply of water for domestic purposes been more liberal, the want of it would not have been so severely felt in case of fire." Whether we regard the health, the morals, or the security of the community, an abundant supply of pure water must be considered a public and a private blessing.

Commending the subject of a watermeter, to the consideration of theingenious, I remain, Sir, yours, respectfully, WM. BADDELEY.

London, March 7, 1839.

TAKING IMPRESSIONS OF DIFFERENT SIZES FROM THE SAME PLATE.

Sir,-In the report of the meeting of the Royal Institution, February 8th, in No. 811, there is a notice of a print having been laid on the table by Mr. Brockedon, remarkable for having impressions of three different sizes taken from the same plate; and it is stated that the process is as yet undiscovered. Allow me to suggest the following as the method by which it is, or at least by which it may, be effected; and I communicate it with the more confidence, from Mr. Brockedon having told me that he believes it to be the plan which is really adopted, and that it has already been suggested by two or three individuals, among whom I believe may be reckoned Mr. Brockedon himself, and Professor Wheatstone.

I imagine then, that an impression is taken from an engraved copper plate in some soft metal, or probably in some more fusible yet ductile alloy, by the French method of stamping, called, En cliche; this impression is used to obtain its reverse in a similar manner, and that these two, thus fitting exactly into each other, are then passed together through the rolling mill until the desired extension is obtained. Of course care is taken that the plates are extended in both their dimensions alike, so as to preserve the original proportions of their sides, and it is probable they may require cautious