only now to proceed to the different papers of the prefent voJume, according to their claffification; commencing with the divifion appropriated to

SCIENCE.

Of the ftrength of acids, and the proportion of ingredients in neutral falts. By R. Kirwan, Efq.

This very elaborate memoir may be confidered as the second edition of a paper on the fame fubject by Mr. Kirwan, formerly inferted in the London Philofophical Tranfactions. He informs us that he has devoted the leifure of ten years to the inquiry, which is undoubtedly of the first importance to the ac curacy of chymical analyfes. When we speak of the proportion of acid, for inftance, in neutral falts, we speak without definite ideas, unless we mean an acid of tome given strength, To introduce this degree of correanefs is Mr. Kirwan's purpofe. He has now fixed, for fandards, on marine acid of 1,500, vitriolic of 20co, and nitrous of 1,5543: but why he should not have used the vitriolic acid of commerce, and the others at pecific gravities, at which they can be readily procured, we fee no fatisfactory reafon. The first tables are intended to fhew how much standard acid any acid liquor of a given density, and at a given temperature, contains:-there is one for each acid. They are conftructed partly on the author's experiments, and partly on M. Pouget's formulæ, as given in a former volume of thefe Tranfactions.-To enter into an examination of the feveral points difcufied in this extenfive effay would not only be a trefpafs on the space which we can allot to any fingle paper, but would prove interefting only to a fmall part of our readers; who, after all, would compare the two editions and decide on the merit of the latter for themfelves. We do not hefitate to believe that the author, by omitting fome precarious hypothetical poftulata, and by an improvement in his method of operating, has made nearer approximations than before. The two following quotations will give fome idea of his prefent principles. On the marine acid, he reafons thus:

100 cubic inches of marine acid air weigh as nearly as I could ellimate 60 grs. barometer 29,6, thermometer 57°, 10 grs. of water abforb 10 of this air, bar. 29,6, ther. 49°. i he fpirit of falt thus formed occupies the fpace of 13,3 grs. nearly; hence its specific gravity is 1,00 nearly, and the ípecific gravity of the pureft marine acid in its condensed state is 3,03.

I could not obferve whether the abforption of this air produced heat; molt probably it did, but this is no proof that the conden fation was greater than that fund by calculation.

The fpecific gravity of the frongest marine acid that can eafily be procured and preferved is 1,196. Ico parts of this will be found by calculation to contain about 49 of that whofe fpecific gravity is

1,500, and which I call the ftandard of the marine acid. The error arifing from condenfation will fcarcely exceed 1 or 1,5 grs. per cent. ; by mixing this fpirit of falt with different proportions of water I have had the refults from which the enfuing table is calculated.'

In investigating the ingredients of neutral falts, he builds this procefs; which, fo far as it goes, is fimple and fatisfactory:

First, I faturate a known quantity of alkali or other bafis with an acid whofe fpecific gravity is known, and whofe proportion of ftandard is determined by the tables. I then make another folu-, tion of a known quantity of neutral falt of the fame fpecies as that formed by faturation, and examine the fpecific gravity of both folutions in the fame temperature, adding water to the ftronger of the two, until their denfities become equal, and thence infer that an equal proportion of falt exifts in both, but the proportion in one of them is known; and therefore the proportion in the other, the weight of the whole being found, is alfo determined. Even this method is fubject to a small inaccuracy, for a flight excess of acid is always left, left any lofs of liquor fhould entue from trials of faturation with vegetable blues, and this renders the denfity of the folution of the regenerated falt fomewhat greater than would enfue from the proportion of falt it contains, befides that in many cafes the proportion of water of crystallization must be discovered by expofure to heat.'

Mr. K.'s converfion to the antiphlogiftic fyftem has alone made a confiderable variation in the matter as well as in the manner of his memoir.

Chemical communications and enquiries. By R. Perceval,

M.D.

Dr. P. divided the products of the diftillation of marine and nitrous acids into three portions. In four experiments with the former, what came over first and last had greater specifie gravity than the middle portion. As marine acid is more volatile than water, the firft portion of acid fhould naturally be more faturated: but why the laft portion fhould be stronger than the intermediate, it is not easy to understand; unless, as Dr. P. conjectures, the vitriolic acid acts on the falt in a more concentrated state at the close of the procefs. In the case of the nitrous acid, the products were of greateft fpecific gravityat firft, and the laft was lighteft. The cauftic volatile alkali had leaft fpecific gravity at firft.

In the observations on the process for dephlegmating the vitriolic acid, (which are not very important,) we apprehend that Dr. P. is miftaken in fuppofing the depofition to be gypfeous. We believe that it is always, at least in part, vitriolated lead.

Account

Account of a chamber lamp furnace. By the fame.

This lamp feems ingeniously contrived; and, by putting it more in the power of perfons who have not an elaboratory at command to make experiments, it may contribute to diffuse the practical knowlege of chemistry. The eflential parts are an Argand's lamp enclofed in a cylindrical body, and furmounted by a truncated cone, which serves as a capfule to hold the fubject of experiment. If the cylindrical body were double, and the interval filled with charcoal in powder, it would probably produce a greater effect, as the furrounding air would not cool it fo faft. We invite ladies and gentlemen, dilettanti in chemistry, to procure a furnace of this conftruction.

Extract of a letter from the Rev Charles Perceval, to Robert Perceval, M. D.

Mr. P. gives a fhort account of an extraordinary conftruction in the eyes of a poor girl, aged 11. Their motion, inftead of a regular horizontal one from fide to fide, is tremulous in all directions, and partly perpendicular, with a prominent motion of the globe of the eye. The child cannot easily fee any object placed above her eyes, but reads perpendicularly from the bottom upward. The whole globe of the eye is of a reddish caft; the white, ftreaked with fainter red; the iris of an uniform deep red approaching to brown. Both eyes are weak and watery, and, when turned from the light, glow with a more vivid colour than when exposed to it.

Defcription of a portable barometer. By the Rev. Gilbert

Auftin.

One of the principal advantages of this barometer is, that the furface of the mercury in the bason is determined more accurately than can be done by floating gages, and there is no wafte of mercury. We cannot convey a fatisfactory idea of this invention without the plate.

Obfervations on the variation of the magnetic needle. By Mr. Thomas Harding.

The refult of Mr. H.'s remarks, during 19 years, is that the change in the variation is uniform at Dublin. From the year 1657, in which it was none, it has been going on at the medium rate of 12' 20" annually, and was, in May 1791, 27°. 23′ weft. He brings proof of his affertion of the uniformity of the variation, from different authentic records, and ftates the operations by which it is calculated. He concludes with recommending accuracy in marking the exifting variation when maps are made, as not only conducing to the exact definition

definition of boundaries, but as laying the beft foundation for a discovery of the longitude by fea or land.

Defcription of an inftrument for performing the operation of trepanning with more eafe, fafety, and expedition than thofe now in general ufe. By Sam. Croker King, Ésq.

After an hiftorical account of the ufe of the trepan and trephine in these kingdoms, with remarks on their feveral defees, Mr. K. defcribes one which is a kind of compound of both.

Defcriptions of a felf-registering barometer, by the Rev. Arthur Macguire, and of a method of cutting fine fcrews, by the Rev. Gilbert Austin, are only to be understood by reference to the plates.

An attempt to determine, with precision, fuch injuries of the head as neceffarily require the operation of the trephine. By Sylvefter O'Halloran, Eiq. Surgeon to Limerick Hofpital.

Mr. O'Halloran arranges his obfervations under fractures of the cranium, and depofits on the furface of the brain, or on its membranes. He felects three cafes of fractured skulls cured without trepanning, and fubjoins two, in which, fymptoms, fupervening many days after the fracture, were removed by the operation. Thefe fymptoms were drowfinefs, coma, and convulfions; and it is their occurrence which feems to him the proper guide for trepanning in fimple fractures. He altogether difapproves the operation in wounds of the full with a cutting inftrument. Fractures with depreffion require the operation in the first inftance; though he fhews, by fome cafes, that it may fucceed after confiderable delay.

With respect to depofits of matter on the furface or membranes of the brain, he confiders them, from his own experience, as almoft certainly mortal, whether the operation be or be not performed. However, he advifes having recourse to the trephine, as the only chance. As to concuffions, he does not agree with Mr. Pott in approving of trepanning in ftupors which immediately follow a hurt; thinking them owing to concuffion only, and not to extravafation. He divides concuffions into three claffes; 1. mortal; 2. where there is recovery with infanity; 3. where there is perfect recovery; and he adds two cafes in which the patients perfectly recovered without any operation.

Demonftration of Newton's theorem for the correction of spherical errors in the object glaffes of telescopes. By the Rev. Dr. Matthew Young.

Newton, in his optics, propofed a contrivance for perfe&ing telefcopes, confifting in cementing together two concavo-con

vex

vex glasses with water between them; and he gives a theorem for their conftruction, by which the reflections on the concave fides of the glaffes will very much correct the errors of the refractions of the convex fide, fo far as they arife from the sphericalness of the figure:-but in this an evident error occurs, arifing from the corruption of Newton's text, which Dr. Y. from an investigation of the demonstration, here corrects.

Account of a fiftulous opening in the ftomach. By G. Burrowes, M. D.

This paper adds one to the cafes on record of wounds in the ftomach remaining unclofed without any irremediable inconvenience. The fubject of the cafe was a man who received a wound from a blunt-pointed wooden inftrument, between the cartilage of the 8th rib on the right fide, and the navel: and which penetrated the ftomach. Much fever and inflammation fucceeded; after which a fiftulous orifice remained, which was kept ftopped with a plug. He lived during 27 years in this ftate, though extremely irregular in his habits; and he ate with good appetite and digeftion. If the plug was withdrawp, the liquids which he had fwallowed partly efcaped through the opening; and, when his ftomach was empty, a fweet whitish fluid adhered to the plug. He had no pain, and no kind of food difagreed with him. After his death, the wound was found to have penetrated the ftomach in the centre of the greater curvature. From the adhefions which it had formed with the liver, colon, and integuments, a ftricture was produced, giving to the ftomach the appearance of a double bag, with the fiftulous opening in its middle. The duodenum was enlarged beyond the fize of the colon, and feemed to have performed fome of the functions of a fecond ftomach. The colon was firmly attached to the ftomach by a ligamentous fubftance.

A cafe of enlarged spleen is next related by the fame writer. It occurred in a man 44 years old, who died of fever with vomiting fix days after admiflion into an hofpital, into which he was taken for a fuppofed dropfical fwelling in the abdomen. On opening, the ftomach and inteftines were found all thrown to the right fide, while the left was entirely occupied by the fpleen, which was neither indurated nor difcoloured, but enormoufly enlarged. When taken out, it measured 14 inches long, and weighed 11 pounds 13 ounces. It does not appear that any fymptoms, befide thofe which were merely owing to weight and preffure, accompanied the amazing increase of this organ. The foft and equable feel of the abdomen might have led even an experienced furgeon to suspect water, and to proceed to tapping; which, Dr. B. properly obferves, would have caufed a fatal hæmorrhage.

The