been dried by a new process, which will enable a botanist in a tropical climate to dry nearly 400 specimens in three days. It is very rich in ferns and grasses, as well as other genera little known as natives of the tropics.

I have, besides, a portfolio of drawings, representing the most striking picturesque and vegetable scenery, together with maps of the different routes pursued.

ART. XXV.-Account of a new Portable Gas Lamp, invented by DAVID GORDON, Esq. Edinburgh*.

THE application of inflammable gas to the purposes of illu

mination, has hitherto been almost wholly confined to the lighting of large cities, extensive manufactories, and public institutions. The ingenious apparatus invented by J. and P. Taylor, for obtaining gas from oil, has enabled gentlemen of fortune to light their houses with gas at a moderate expence, and without being annoyed by any of the disagreeable products which arise from the distillation of coal. But notwithstanding this valuable improvement, gas light has never been rendered portable, and the great body of private individuals, and all the lower classes of society, are unable at this moment to derive any advantage from the extraordinary cheapness of this beautiful light.

In order to remove these limitations to the use of gas lights, and to render them available in every case where lamps or candles can be used, Mr Gordon conceived the idea of condensing a great quantity of gas into a small space, and set himself to construct a lamp, in which this condensed gas could be burned with the same facility and security as an ordinary lamp. The body or reservoir of the lamp, which we have represented in Plate IX, Fig 1. and 2. is commonly made of copper, about th of an inch thick, in the form of a sphere or a cylinder, with hemispherical ends. This reservoir may be put into a different apartment from that which is to be illuminated, or may be concealed

Mr Gordon has secured by patent the exclusive privilege of this invention. We have been enabled to draw up the following short account of it from information communicated by the Inventor.-Ed.

under the table, or, when it is required to be ornamental, it may be put into a statue, or the pedestal of a statue, or may be suspended, as in Fig. 2.

In order to regulate the escape of the condensed gas, Mr Gordon has employed two different contrivances, which are extremely ingenious. The first of these is a stop-cock, Fig. 5. constructed in the following manner: After the cock has been drilled through in the usual manner, the circular hole in the key is contracted at one side, by soldering into it two pieces of brass, which join at one side a of the hole, and are about th of an inch distant at the other side, as at b c, forming an acute angular aperture, (Fig. 7.) By this means the issue of gas can be regulated to the smallest possible stream, by bringing the acute angle a of the opening in the key to communicate with the circular opening in the cock; and as the expansibility diminishes as the gas is consumed, the aperture can be increased in the same proportion. But to secure the above object more completely, and to prevent the possibility of turning the cock suddenly, so as to admit too great a discharge of gas, a ratchet wheel is fixed in the end of the key of the cock, in which an endless screw m n, Fig. 5. works. By turning this screw with the nut N, the flame may be enlarged or diminished to any extent, however highly condensed the gas may be.

The second contrivance which Mr Gordon employs to produce the same effect, is a conical leather valve, similar to that in the reservoir of an air-gun, placed in the opening of the reservoir of the lamp, where it screws on to the condensing pump. When the reservoir has been charged with gas, and removed from the pump, a set of brass, Fig. 6. is screwed in above the valve. Through this piece of brass there passes a finger-screw, the point of which, when made to press on the valve, forces it back, and allows the gas to issue in any quantity that may be required. A bridge of brass a b, consisting of a hollow tube, in the form of a Gothic arch, passes over the head of this regulating screw, for the purpose of giving freedom to the fingers in turning the screw to regulate the flame, and to conduct the gas to the burner, which, in a standing lamp, is screwed on at the centre c of the arch.

By either of these contrivances, the latter of which Mr Gordon prefers from the simplicity of its construction, the com

mand of the flame is so complete, that it may be reduced to an almost imperceptible quantity.

The forcing-pump by which Mr Gordon condenses the gas is nearly the same as that of the common condensing syringe, having a solid piston worked by a lever, with shears and a guide, to produce a vertical motion. As a considerable degree of heat is created during the condensation of the gas, the pump must be kept cool by surrounding it with a case filled with water, and changing the water as soon as it becomes heated.

When it is required to fill a great number of lamps with condensed gas, which will no doubt be the case, when it is sold to individuals from the reservoirs of Gas Light Companies, Mr Gordon recommends that the forcing-pump should be wrought by steam, or any other mechanical power, and that the gas should be condensed into a large reservoir, from which the lamps of numerous individuals may be filled at once with the condensed gas. A mercurial gage, similar to that used for ascertaining the force of condensed air, must be fixed to the large reservoir, for the purpose of enabling any person to see the degree of condensation to which the gas has been brought.

As we have had occasion to see Mr Gordon's lamp put to the test of direct experiment, we feel ourselves entitled to speak with confidence of its excellence, and to recommend it as one of the greatest practical inventions which has for some time been presented to the public. Its application to the lighting of private and public carriages, as well as to coal mines, under the safeguard of Sir H. Davy's invention, will be speedily put in practice; and we hope the time is not very distant, when reservoirs of condensed gas shall be established in every town and village of Great Britain, and when the lonely cottages of the poor shall be enlivened by this economical and chearful light. There is one application of the portable gas lamp to which we attach a very high value. By an extreme diminution of the aperture, the flame can be rendered so small (in which case it is reduced to a blue colour) as to give no perceptible light, and to occasion almost no consumption of gas. In this state the lamp may be used in bed-rooms, and the imperceptible flame may at any time be expanded into the most brilliant light, by turning the cock, by means of a metallic rod terminating near the bed.

Description of the Figures in Plate IX.

Fig. 1. is one of the Portable Gas Lamps, 6 inches in diameter and 9 inches high, exclusive of the hemispherical ends and burner at the top. When filled with coal gas condensed 25 times, it will supply a lamp equal to 5 candles, 6 to the pound, for 6 hours; and when filled with oil gas, it will burn for about 12 hours.

Fig. 2. is a sphere of 12 inches diameter, and filled as Fig. 1. will, with two argand burners, equal to 12 candles, burn for upwards of 6 hours with coal gas, and 12 hours with oil gas. Fig. 3. contains a cylinder 6 inches diameter and 2 feet high, exclusive of the hemispherical ends, and is calculated to supply an argand burner, equal to 10 candles, for 6 hours with coal gas, and for 12 hours with oil gas.

N. B. Although gas made from oil burns longer than that made from coal, yet it is doubtful if the great difference mentioned above does not arise principally from using burners pierced with smaller holes.

Fig. 4. is the reservoir of condensed gas, for supplying lamps with facility. At A, where the gas is to be allowed to issue from the condensed reservoir, the valve is placed. B is the finger-screw to raise the valve. C the perforated male screw, upon which the lamp is to be screwed.

Fig. 5. is the stop-cock, which is constructed as already described.

Fig. 6. is the set of brass, already described, to be screwed on when a valve is used.

ART. XXVI.-Notice of the Progress of Botanical Science in Bengal, being the substance of a Letter from Dr WALLICH, Superintendant of the Botanical Garden near Calcutta, to FRANCIS HAMILTON, M. D. F. R. S. & F. A. S. L. & E.

SOON after Dr Wallich's appointment to the Botanical Garden

near Calcutta, he obtained the permission of Government, and the sanction of the Honourable E. Gardner, Resident at Kathmandu,