centre which I have never seen in any prismatic spectrum. It is a kind of light brown, resembling the colour of a certain sort of Spanish snuff. The 170 feet object glass showed the same colour also very clearly.

XIII. Of the Order of the Colours.

The arrangement of the colours in each compound ring or alternation, seen by reflection, is, that the most refrangible rays are nearest the centre; and the same order takes place when seen by transmission. We have already shown that when a full dilution of the colours was obtained their arrangement was violet, indigo, blue, green, yellow, orange and red; and the same order will hold good when the colours are gradually concentrated again; for though some of them should vanish before others, those that remain will always be found to agree with the same arrangement.

If the rings should chance to be red and green alternately, a doubt might arise which of them is nearest the centre; but by the method of dilution, a little pressure, or some smali increase of the focal length of the incumbent lens, there will be introduced an orange tint between them, which will immediately ascertain the order of the colours.

In the second set of rings the same order is still preserved as in the first; and the same arrangement takes place in the third set as well as in the fourth. In all of them the most refrangible rays produce the smallest rings.

XIV. Of the alternate Colour and Size of the Rings belonging to the primary and dependent Sets.

When two sets of rings are seen at once, and the colour of the centre of the primary set is black, that of the secondary will be white; if the former is white, the latter will be black. The same alternation will take place if the colour of the centre of the primary set should be red or orange; for then the centre of the secondary one will be green; or if the former happens to be green, the latter will be red or orange. At the same time there will be a similar alternation in the size of rings; for the white rings in one set will be of the diameter of the black in the other; or the orange rings of the former will be of equal magnitude with the green of the latter. When three sets of rings are to be seen, the second and

third

third sets will be alike in colour and size, but alternate in both particulars with the primary set.

The same thing will happen when four sets are visible; for all the sets that are formed from the primary one will resemble each other, but will be alternate in the colour and dimensions of their rings with those of the primary set. [To be continued.]

XIX. Report of Surgical Cases in the City and Finsbury Dispensaries for September 1807. By JOHN TAUNTON, Esq. In the month of September there were admitted on the books of the City and Finsbury Dispensaries 237 surgical

:

One of the fatal cases was that of Mrs. M. S. æt. 67, who, soon after the birth of her ninth and last child, was seized with femoral hernia: the tumour was small, but painful, attended with sickness and inclination to vomit; these symptoms did not last long, as the hernia receded without assistance she had another attack in about six weeks, which was also of short duration; the hernia soon became irreducible, and she had been exposed to similar attacks for the last sixteen years of her life, for which time it had never been completely returned: these were occasionally longer and more severe; the symptoms frequently continued for two or three days, but were removed without any operation or medicine, except some Daffy's elixir.

On the 22d of August she was seized with the usual symptoms, viz. pain over the whole belly, particularly in the region of the stomach, with a sensation of heat, vomiting, cold sweats, intermitting pulse, and suppression of stools for four days: the tumour was now much larger than before, being nearly the size of a child's head at birth: at this period she had a motion of a small quantity of feculent

matter,

matter, after which the bowels were confined for three days, when she was taken with diarrhoea, an acute pain in the bowels, cold sweats, pulse variable, vomiting of feculent matter; but the hiccup was not very distressing :-these symptoms continued for nine days, being sixteen from the attack, when she sunk under the disease.

The medicines given during this illness were, opium, calomel, extract. colocynth. cum calomel. enema communis, and the enema cum nicotiana. She could not be prevailed on to submit to the operation.

per

On dissection, the intestines were distended with flatus, the colon was much enlarged and inflamed, part of the sygmoid flexion was contained in the hernial sac, but not the whole circumference of the intestine, which left the canal vious. The adhesions were firm around the mouth of the sac, from which the intestine could not be separated, and the coats were much thickened by inflammation which approached to gangrene. The omentum was much inflamed and adhered to the hernial sac; and that part of the omentum within the sac was much enlarged and more firm, which, together with the adhesions, had rendered this an irreducible hernia,

Greville-street, Hatton-garden,

February 23, 1808,

JOHN TAUNTON,

Surgeon to the City and Finsbury Dispensaries, Lecturer on Ana, tomy, Surgery, Physiology, &c;

XX. Proceedings of Learned Societies.

ROYAL SOCIETY.

On the 5th of February, a letter from Mr. Knight, to the president, was read, on the inconvertibility of the bark of trees into the alburnum. The author, as usual, detailed the effects of a great many experiments made to confirm this opinion, which he announced in the conclusion of a letter read before the Society last season, (see Philosophical Magazine, No. 109, vol. xxviii. p. 43.) One of the most obvious reasons assigned for the truth of this opinion was, that many trees having barks very dissimilar, have wood very similar; and that, had the alburnum been formed of the bark, the wood must consequently have been as different as

the bark was. On the other hand, many trees with bark very similar, have wood very different. These facts, in conjunction with some minute experiments, Mr. Knight concluded as decisive that the bark is not transmuted, as Malpighi supposed, into alburnum; but that each performs its peculiar function in the economy of vegetation.

February 11 and 18. Several mathematical papers on the properties of a circle, &c., were presented to the Society by the astronomer royal, but were not of a nature to be read. A curious paper on cranites, or the idiotism of the inhabitants of alpine regions, who are affected with goitres, or swellings about the head, was read. From the author's researches among the people of Switzerland, and his investigation of the supposed connection between this species of mental imbecility and goitres, (which are generally ascribed to the effect of using snow-water on the glands,) he was led to conclude that cranites exists frequently where there are no goitres, and that many families suffer the latter complaint without experiencing the former.

February 25. A. Marsden, esq., in the chair. A gcological paper on the whin-dykes in the north of Ireland, in a letter to Mr. Davy, was laid before the Society.

A continuation of Mr. Home's experiments on the functions of the spleen was read, in which this able naturalist operated on asses with extract and tincture of rhubarb, as related in his former experiments on dogs. The spleen and the colon were found impregnated with the rhubarb, when none was found in the liver. Several curious experiments were made to ascertain the quantity of serum and of rhubarb found in the blood in the vena cava, the left auricle of the heart, and other members: but the results are not satisfactorily established.

A letter from Mr. Murdoch, to the president, was read, containing an account of the origin, progress, and present state of gas-lights. It appears that so long ago as 1739 Dr. Clayton, in the Philosophical Transactions, discovered the inflammability of gas procured from coals: but this knowledge was never adapted to practice till about sixteen years ago, when the author, at a foundry in Cornwall, first proposed

proposed the application of this gas-light to economical purposes, and actually earried it into effect. In 1798 he also established it on a larger scale at Messrs. Bolton and Watts, Soho, Birmingham. But at Messrs. Phillips and Co's cotton factory it has been carried to the highest degree of perfection, and on the most extensive scale, of any place iu the kingdom. From a statement of the relative expense of candles and gas, it appears that for the light which that manufactory required, 2000l. a year would be expended in candles; whereas the wear and tear and expenses of gaslights do not much exceed 600l. a year, ainounting to about one-third the expense of candles.

IMPERIAL ACADEMY OF SCIENCES AT ST. PETERSBURGH.

This Academy has published the 13th volume of their Memoirs. It contains, among other interesting articles, a description of the celebrated silver mine of Zuseoff, ou Mount Athol, in Siberia, with an account of the total produce of that mine from 1747 to 1793 inclusive.

UNIVERSITY OF WILNA.

This body has announced the following as the subject of a prize question: "What are the chief diseases of plants, and what analogy exists between them and those of aniinals?"

The prize is 100 ducats; and the memoirs, written in Latin, French, or Polish, must be sent before the first of September 1808 to the rector of the University, under cover to Messrs. Reiser or Karner, bankers in Wilna. The prize will be adjudged in the month of January 1809.

XXI. Intelligence and Miscellaneous Articles.

NEW PROCESS FOR PREPARING CALOMEL.

An important improvement in the preparation of that esAN sential article of the pharmacopoeia, calomel, has been recently introduced by Messrs. Luke Howard and company, chemists. It consists in a peculiar mode of conducting the final sublimation by fire; by which the vapour of the calo

mel,