known of what breadth the narrowest part of the ring appeared at this place (about 54° 53' 53" N. and about 1° 24' W.). The mountains fully covered it, and I believe were higher than it a little. This observation was made with a 42-inch reflector, (Newtonian) with 5.75 inches aperture. As I did not expect so rare a sight, and there was not time to get the wire or divided eyepiece micrometer after it was seen, I regret to say no measures were taken of the heights.

I may mention another circumstance which was not overlooked, namely, the appearance of the solar spots during the eclipse, which afforded the most favourable opportunity of examining them to advantage. My observations were made with the view of ascertaining whether any difference in shade could be seen similar to the lunar cavities, or whether anything which indicates a rise above the solar surface; but not the least could be observed, or even imagined to be visible. Though I have examined the solar spots regularly for ten or twelve years, I never saw them to greater advantage than on that occasion.

I will close this letter with an observation upon the aurora borealis which was visible at this place on the 22nd of April 1836, at 10 45 P.M. It appeared directly overhead in the form of a star of great magnitude of not less than 90 degrees diameter, with numerous rays shooting every way, those to the north appearing of a deep red colour. With attentive examination I could not discover the least darting or motion of the rays at one time, which if so, is not easily accounted for by the principles of electricity. A very similar appearance is represented by a plate in the Journal of the Royal Institution. Your humble Servant, High Barns, near Sunderland, May 26, 1836.

W.ETTRICK.

BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE.

The next Meeting will be held at Bristol during the week commencing on Monday, August 22nd; the Members of the General Committee will assemble on the preceding Saturday.

METEORS OBSERVED IN INDIA IN 1832.

The following notices are derived from "Extracts from a Journal of a Residence, and during several Journeys, in the Province of Behar, in the years 1831 to 1834. By Mr. J. Stephenson," which appear in the Number for December, of the Journal of the Asiatic Society of Bengal, vol. iv. p. 713.

Beautiful Meteor observed near Singhea, Tirhut, April 11th, 1832.

At 4 hours 45 minutes A.M. and at daybreak, observed a meteor in the form of a globular ball of fire, which passed through the air, from west to east, in a horizontal direction, and with a motion moderately rapid. Its size appeared to be about a foot in diameter, having a fiery train of the most splendid brilliancy apparently many yards long. It illuminated the country as far as the eye could reach, and remained visible for five seconds, after which it exploded

like a rocket throwing off numerous corruscations of intense light; but without any report or noise of any kind. Its apparent elevation inconsiderable.

Another beautiful Meteor observed at the same Village on the 20th of May, 1832.

At 6 hours 40 minutes P.M. a large pear-shaped meteor was observed shooting very rapidly in a horizontal position, and in a direc. tion from north to south. Nothing could exceed the brilliant mixture of green, tinged with blue colours, exhibited during its rapid progress. It left a luminous train of great length behind, and remained visible about three seconds, then disappeared in the southern horizon, without exhibiting any signs of exploding.

ANALYSIS OF PLOMBGOMME.

BY M. DUFRESNOY.

The compound of oxide of lead and alumina, called by mineralogists plombgomme, on account of its resemblance to drops of gum which exude from trees, has hitherto been found only in Huelgoat mine in Brittany. It has, however, lately occurred in a lead mine near Beaujeu : it is found in small mammillated masses, with slightly varying textures; some are of a yellowish white colour, externally very shining, and the fracture is both splintery and testaceous, without any trace of crystallization; others are slightly greenish, composed of concentric layers, and possess a radiated structure, like wavellite. When observed with a microscope, the fibres appear to be crystalline, with a rhombic fracture, like some arragonites.

The hardness of plombgomme is intermediate as to that of carbonate and phosphate of lime. Its specific gravity is 4.88: before the blowpipe it decrepitates; on charcoal it swells and yields a scoria. ceous white enamel.

By analysis it yielded

-100-00

The specimen subjected to analysis contained phosphate of lead: it is very probable that the phosphoric acid found indicates a certain quantity of phosphate of lead mixed with the plombgomme. On this supposition, the analysis should be thus stated:

Silica...
Alumina....

2.11

Deutoxide of lead.

34.23 .37.51

ON THE ACTION OF IODINE ON ORGANIC SALIFIABLE BASES.

M. Pelletier in a paper on the action of iodine upon strychnia, brucia, cinchonia, quina, and morphia, remarks that being unacquainted with the action that the halogenous bodies, and chiefly iodine, bromine, and chlorine, exert upon the salifiable organic bases, we do not know whether these bodies can combine with the vegetable alkalies without decomposing them or not.

In endeavouring to elucidate this point he has arrived at the following conclusions. That iodine combines with most of the organic bases in atomic proportion: thus, strychnia affords a crystalline and coloured iodide composed of 2 eqs. of iodine and 1 eq. of strychnia; brucia forms two iodides, one composed of 2 eqs. of iodine and 1 eq. of brucia, the other of 4 of iodine, to 1 of base; whilst cinchonia and quina each combine with iodine in the proportion of 1 eq. of iodine to one of base.

That iodic acid combines with the organic bases, forming neutral and acid salts, in which the acid and base exist in the same proportion as their respective iodides.

That hydriodic acid unites with the organic bases, forming salts which have a tendency to an excess of base; thus, the hydriodates of brucia and strychnia are (sesquibasic) subsesquisalts without water of crystallization. The organic hydriodates are decomposed by iodic acid, iodine being liberated, whilst the hydriodate is converted into an iodide.

The action of iodine upon morphia forms a very singular exception to the above, for one part of the iodine combines with hydrogen from the morphia to form hydriodic acid, whilst the other portion of iodine unites with the substance resulting from the morphia. When morphia is acted on by iodic acid, the acid loses its oxygen, which unites with one portion of the morphia, forming a red substance like that resulting from the action of nitric acid on morphia, whilst the iodine evolved acts on the other portion of morphia as it does by direct contact; but the resulting combination is decomposed by a fresh portion of iodic acid, and entirely converted into iodine and the red substance.-L'Institut, 2nd March.

ON A NEW MODE OF ANALYSIS OF CLOSELY AGGREGATED

MINERALS.

Dr. Abich states that when carbonate of barytes is heated to whiteness, it fuses and is deprived of the whole of its carbonic acid; and this property he has very advantageously employed in the analysis of minerals, its caustic power being so great that it quickly and completely decomposes the aluminates and corundum, bodies which are with the greatest difficulty acted on by pure potash; and cyanite, staurolite, andalusite, cymophane, zircon, and the felspars are also acted upon in the most complete manner. To conduct the analysis successfully, the following precautions are necessary. A furnace by which an extremely high and well-regulated temperature can be obtained in a short time. The mineral reduced to powder, which need not be

extremely fine, levigation being useless, must be mixed with from 4 to 6 times its weight of pure carbonate of barytes, and placed in a platinum crucible; this is then inclosed in a Hessian crucible covered and luted, which placed on any convenient support in the furnace must be heated to whiteness, and kept at that temperature for from 15 to 20 minutes: a perfectly fused mass is obtained, which dissolves with facility in diluted muriatic acid.-Annales de Chimie, December 1835.

ON SOME NEW COMBINATIONS OF CARBOHYDROGEN OR

METHYLENE.

MM. Dumas and Peligot have succeeded in obtaining some new combinations of carbohydrogen. The first, hydrofluate of carbohydrogen, may be obtained by gently heating a mixture of fluoride of potassium and sulphate of carbohydrogen; sulphate of potash is formed, and a gas evolved which collected over water is deprived of all foreign substances, and is then pure hydrofluate of carbohydrogen. It is colourless, of an agreeable æthereal odour, and burns with a flame similar to that of alcohol, but rather more blue. By its combustion hydrofluoric acid is formed, the vapours of which are diffused in the air. It is slightly soluble in water, 100 parts of water at 60° Fahr., dissolving 166 of this gas. The analysis of this gas indicates its composition to be

One volume of carbohydrogen

One volume of hydrofluoric acid

0.4904 0.6788-1.1692

According to this, hydrofluate of carbohydrogen, like the hydrochlorate of that base, contains as well as hydrochloric æther, 1 vol. of acid and I of carburetted hydrogen condensed into one volume.

When a mixture of pyroxylic spirit, nitric acid, and nitrate of silver is boiled in the proportions used in making fulminating silver, or in any other proportion, no action takes place before the evaporation ofths of the liquor, unless the nitric acid is very strong and the operation is conducted in a retort, when amongst the volatile products abundance of nitrate of carbohydrogen is found. Towards the end of the operation, when the solution is so concentrated that the nitrate of silver would become solid by cooling, by continuing the ebullition lively action takes place, much hyponitrous acid is liberated, and there is deposited a white powder. This detonates with difficulty by a blow, and deflagrates feebly when placed in contact with hot coals, from which MM. Dumas and Peligot at first considered that it contained fulminating silver; but a more attentive examination showed it to be oxalate of silver.

By adding pyroxylic spirit to the acid nitrate of mercury, a considerable quantity of a yellowish white and resinous-looking substance is immediately deposited, which by boiling for a long time with concentrated nitric acid, produces a white powder which is perfectly pure oxalate of mercury.

On an analysis the substance formed by the immediate action of pyroxylic spirit on nitrate of mercury gave from 1.025, water 0.024 and carbonic acid 0.180. 0.600 gave by protochloride of tin, and

1

hydrochloric acid, 0-452 of mercury. 0-700 afforded 18 cubic centim. of damp azote at 54° and 0.75. These results are equivalent to

4 eqs. 4.53 2 eqs. 0.37 2 eqs. 74.80

This leads to so complicated a formula, that they merely give it without insisting on its correctness :

2 (C+ H2 O3, H gO) + Az2 O3, H g2 0,

which would indicate the existence of a compound of 2 eqs. of formiate of mercury and 1 eq. of nitrate of mercury.

By passing anhydrous sulphuric acid into pyroxylic spirit, diluting the liquor, and supersaturating by barytes, there are obtained sulphate of barytes, which precipitates, and sulphocarbohydrate of barytes, which remains in solution. The solution freed from excess of barytes by carbonic acid, and being concentrated at a low temperature and then suffered to crystallize spontaneously, furnishes truncated prisms very thin and long, which appear to have a rhomboidal base.

In the same circumstances the common sulphocarbohydrate of barytes affords very different crystals; but the composition of the salt produced from the anhydrous acid does not differ from the salt afforded by the common acid. This salt is composed of

The calculation was founded on the formula

BaO, SO3 + C+ H+, S O3, H2 O.

It appears then that a series of isomeric sulphocarbohydrates exist, resulting from the action of sulphuric acid on pyroxylic spirit. Tartrocarbohydrate of barytes may be obtained by mixing a solution of tartaric acid in pyroxylic spirit, and a solution of barytes in the same spirit together, and washing the precipitate with anhydrous pyroxylic spirit. It is composed of

This salt is in a gelatinous state when formed in the pyroxylic spirit, but when washed with water it becomes granular and is converted into tartrate of barytes.

The oxalic, acetic, and benzoic acids dissolved in pyroxylic spirit, and added to barytes likewise dissolved in spirit, produce merely their respective salts, the two latter anhydrous.