plan now in use. I need scarcely say that in the ordinary modes of heating water, only a small portion of the whole bulk of the fluid is in contact with the heat applied. Thus in the following diagram (fig. 1) let A A A represent the lower line and sides of the vessel containing the fluid

A

B

Fig. 1.

to be warmed, then B B B may be fairly assumed to show the line of the heat. For ordinary purposes this answers very well. Unless such great economy of fuel, as will

quite cover the cost of mechanism and increased expense of cleaning a multiplied instead of a plain surface be absolutely called for, it is not worth while to alter the arrangement. Here, however, such a change is demanded; and, in the bath recommended, the heat is

applied as described in the following paragraph, and shown in the diagram (fig. 2), and drawing of section of the bath (fig. 3).

In the annexed diagram and sectional drawing (fig. 2 and fig. 3), A A indicate the reservoir for the water, having in the centre a well, B B, which again communicates with the outer edge and lower surface of the reservoir by means of eight radiating tubes, C C. In the centre of the well is a chamber, D, for receiving and confining the heat. It is in the form of a four-armed

cross, open below to the flame of the lamp, over which the bath is placed. The water is poured into the reservoir, and fills the shaded part (fig. 2). The arrows (fig. 2) show the direction of the flame, which acts almost simultaneously on the inside of the chamber, D, on the tubes, C C, and on the bottom of the reservoir, A A.

It will, I hope, be seen from this description that the heat is so distributed into the middle of the water, so diffused, as it were, through the whole mass, that a very slight amount of caloric, thus imprisoned in the very body of the fluid, acts with great rapidity, quickly passing along

the tubes E E, and from the chamber into the upper stratum, which is itself heated at the same time. A much larger surface is thus exposed to heat than could be done with a bath of the same size on the principle laid down in the first diagram.

The heat is procured by means of a ring-flame lamp, which in outward appearance somewhat resembles the well-known Russian or blast lamp. In this (fig. 4) all communication between the two chambers is done away

with, and, as a matter of course, the blast pipe. Instead of this the upper rim of the outer chamber is pierced with a row of small holes, A A A, through which the steam of the spi rit, heated from the inner chamber, escapes, and, coming in contact with the flame from the inner chamber, takes light and forms a series of blazing jets, which act with great quickness and steadiness. The advantages of this lamp are, that the violent heat arising from the blast lamp when the opening of the pipe has been worn too large, and the roaring made by the strong

single current, are avoided; that in consequence of the blast being broken up, the heat, though the flame is turned inwards, is applied more gently and uniformly, and that there is less risk of the bath being acted on. The bearing-ring has been made much stronger than that of the Russian lamp, to secure it against bending, and is securely pinned to prevent the weight of the bath causing it to slip. Quite recently some further improvements have been introduced. The pipe by which the spirit is poured into the outer chamber is now bent at a right angle, so as to ensure greater facility for introducing it quickly and avoiding waste, and it is now stopped by means of a brass plug, which fits very accurately, and thus, when simply dropped in, cuts off all escape of spirit vapour. Formerly a cork was used, but this was found to char; and a wooden plug which was substituted proved to be anything but an improvement, as, owing to its less compressible nature, it did not hold like cork. The screw-cap used for the Russian lamp is apt to get fixed, and after a short time the thread of the screw often wears. The orifices A A A have been sloped more inwards, so that the jets might impinge more directly upon the central flame; the metal casing of the outlets. has been hardened by hammering, so that they may not wear and gape, as even a very slight change of this nature rapidly weakens the force of the blast, and the flange at the bottom of the lamp has been widened and made heavier, so that it is less easily overturned. All these changes have necessarily had the effect of somewhat increasing the original price of the lamp. But there was

no alternative; efficiency and safety are of such importance in an apparatus of this kind, that I think every consideration ought to be sacrificed in order to secure them.

So great is the heat thus generated, and so effectively is it disseminated through the water, that the latter boils with a rapidity which rarely fails to excite surprise in those who see it. Ordinary hot water, 140° to 150°, passes into violent ebullition in about two minutes, and in some of the baths cold water boils in three minutes. To secure this result, however, the flame must first of all be suffered to rise under the pressure of the vapour from the outer chamber, and indeed this precaution is really necessary in all cases, to prevent the bath, when placed in the bearing-ring, putting out the flame. In order to appreciate the full importance of securing this great heat, it must be borne in mind that it is not only necessary the water should boil, but boil rapidly, otherwise the vapour will certainly not be driven off quickly enough for the purposes of the bath.

At first the bath was heated by means of a Russian lamp, but with a considerable alteration, and I hope I may say improvement, in it; and as this lamp is still retained for some purposes, it had better be described here. As made under my directions, it consists (fig. 5) of a brass cylinder A A, 2 inches in diameter, closed at the bottom, containing a second cylinder, B B, & inch less in diameter, which divides it into two chambers. The outer one communicates with the inner by means of a fine tube of metal, C, which rises from the floor of the latter. On one side of the outer chamber is the handle,