two last numbers, have excited much interest, we shall lay before our readers the following observations which have been previously made on the subject, and which have been sent us by a correspondent. "Carbon, says Sir H. Davy, whether coherent as charcoal, or in powder, is infusible by any heat that has hitherto been applied. I have exposed it to the powers of intense ignition of different voltaic batteries; that of Mr Children, mentioned page 151., one of 40 double plates 18 inches square, and the battery of 2000 double plates, both in vacuo and in the compressed gases, on which it had no power of chemical action. A little hydrogen was given off from it; it slowly volatilized in these experiments, and the part remaining was much harder than before, so as in one case to scratch glass; the lustre was greater; but its other properties were unaltered; there was no appearance of fusion. Dr Clarke exposed a diamond of 6 carats, of an amber colour, to the flame of the gas blowpipe. It became colourless and transparent, after this it became white and opake, and by continuing the heat, it was entirely volatilized in about three minutes. Glance-coal from the Calton Hill, according to Mr Sivright's experiments, when heated in the focus of an 18 inch silvered mirror, was slowly volatilised, but there was no appearance of fusion. The substance found under the gas retorts was volatilized in the same way with a slight smell of ether, but it was not fused. Dr Clark says, that the fusion of plumbago with the gas blowpipe was attended with a vivid scintillation. The surface was covered with a number of minute globules; some of which exhibited a limpid and highly transparent glass, others a glass of a brown hue; the larger globules being jet black and opake, with a dark metallic lustre. With the common blowpipe, Mr Sivright found that black globules were formed on the surface of plumbago, but no transparent ones. In the focus of the mirror it became brown, with small white specks and black globules on its surface. The globules are probably an iron slag. They are hard enough to scratch glass. The white specks are perhaps silica, or some earth which the heat obtained in this way is not sufficient to fuse."

27. Cagnard de la Tour's Experiments on the Vaporisation • of Fluids. In our last volume, p. 199, we gave a general notice of these curious experiments. M. Cognard de la Tour has

prosecuted the subject to a greater length, and obtained several interesting results. When one of his tubes, containing water and a little sulphuret of carbon was heated, the water became at first milky, then transparent, with a slight green tinge, and afterwards almost black by increasing the temperature. The sulphuret of carbon became lighter than the water during the experiment, and floated on it some time before it became all vapour. As the tube cooled, the green colour diminished, and the fluids took their first state, the water having a yellowish tinge. When a little chlorate of potash was put into the tube along with the above fluids, the heat first dissolved the salt; but upon cooling, the water became milky, and the floating sulphuret of carbon fell to the bottom with the crystallizing salt. At a higher heat, the liquor became suddenly of a pure lemon-yellow colour, accompanied with effervescence, and the formation of an oily-looking globule; which, on cooling, remained liquid at the bottom of the tube, without any crystals being formed. With a still higher heat, the yellow liquid disappeared, and was replaced by a small globule of liquid sulphur, which, by additional heat, assumed the colour and transparency of ruby, but resumed the appearance of sulphur by cooling. No trace of sulphuret of carbon appeared in the tube, excepting that, at a certain heat, the water became bluish, though it was always colourless when cold. This coloration did not appear in another tube, where the proportion of chlorate of potash was greater. Small acicular crystals sometimes formed in these tubes in groups of five or six about a central point; and once the whole mass was crystallized. When the water was alone, the transparency of he glass was always affected, but never along with other substances. The sulphuret of carbon goes into vapour at 220° of Reaumur, the proportion of fluid to the contents of the tube being as 8 to 20. It then exerts a pressure of 77.8 atmospheres, the pressure gradually increasing with the heat both below and above 220°. The following results were obtained with Ether, when the volume of liquid was 7, and that of the tube 20.

When the volume of ether was 31, and the tube 20, he ob

28. Characters of Amber.-1. Amber has never the lengthened or drop-form of the gum animi, or other substances with which it may be confounded. 2.Amber has always a richer colour than the resins, &c., which are comparatively watery, thin, and feeble in colour. 3. It has a peculiar lustre, indicating a higher refractive power than resins, &c. * 4. Amber, on rubbing, gives out a different smell from the resins, with which it might be confounded. 5. Both resins and amber are electric. 6. If the specimen is held against a red-hot iron, the smell of the smoke will distinguish it from the resins or gum animi, gum opal, &c. 7. Haüy's Drop Character is not good.

29. Rose on Felspar, Albite, Labradorite, and Anorthite.-M. Gustavus Rose of Berlin, has published a highly interesting and elaborate paper, in the Annalen der Physik, &c, of Gilbert, for February 1823, on the substances formerly comprised under the name of Felspar, which he divides into four species, viz, Felspar, Albite, Labradorite, and Anorthite, differing from each other in their form, and in several other characters, as also by the results of their chemical analysis.

* Amber has a lower refractive power than several of the gums.-ED.

The most remarkable differences are contained in the following Table:

Hemi-prismatic. Tetarto-prisma- Tetarto-prisma- Tetarto-prisma-
-Mohs.

tic.-Mohs.

tic.-Mohs.

tic.-Mohs.

Measures of the principal Angles, referring to the figures of

To 2.581. To 2.619. To 2.7025. To 2.763.

Mr Rose has given the following chemical formulæ along with

the analyses.

Of these, Felspar is said to occur most commonly; Albite, besides the Swedish localities, is mentioned from Arendal, from several places in the Alps, from Kerabinsk in Siberia, Scotland, &c.; Labradorite is noticed from the coast of Labrador, and from Ingria; Anorthite has hitherto been found only in blocks of limestone from Monte Somma.

We understand that almost a year before the publication of this paper, M. Mohs and M. Haidinger had obtained nearly the same results as to the differences prevailing among the forms, specific gravity and other properties of these substances, and considered them accordingly as different species (Edinburgh Philosophical Journal, No. XVI. p. 287.), with the exception only of Anorthite. But they observed some difference in the angles of certain tetarto-prismatic varieties from the Alps, and in their specific gravity, which is between 2.5 and 2.6, and very likely may lead to the establishment of another species, The last of these is probably the same as that which has been observed by M. Breithaupt of Freyberg, in some varieties from Töplitz, in Saxony, and of which he intends to give a full description in a particular paper on these substances. Messrs Brooke, Levy, and Phillips, have likewise ascertained the dif ference between some of the above mentioned species; and Mr Brooke has given the name of Cleavelandite to what formerly had been called Albite. From the united labours of so many mineralogists, directed towards the same object, we may expect in a short time to become more intimately acquainted with these substances; and we are perfectly convinced, that it would be a matter of the highest importance to join with these inquiries such as are directed towards their optical properties.

ZOOLOGY.

30. The Woodcock.-Our friend Major Morison remarks in a letter to us, that there are "few birds among the migratory class, whose character, under this head, invites a greater field for speeu