previously cooled in mixtures made of marine acid with vitriolated natron, muriated ammonia, and nitrated kali, in the proportions mentioned above, this being much cheaper than thofe made with diluted nitrous acid, and very nearly equal in effect,'

Our author has found, that the beft proportions of the mixed powder of crude fal ammoniac and cubic nitre, with water, are 5 to 8. It finks the thermometer from 50° to 11°.

Art. XX. Catalogue of a fecond Thaufand of new Nebula and Clusters of Stars; with a few introductory Remarks on the Construction of the Heavens. By William Herfchel, LL. D. F. R. S.-Mr. Herschel continues his defcription of the nebula, and endeavours to prove that these groups cannot have been ac cumulated accidentally. The greater number of nebulæ are round, gradually increafing in brightnefs towards the center, and feemingly confifting of ftars uniformly fcattered, and regularly approaching each other. The fmaller and less refolvable nebula seem to confift of ftars at a greater diftance from us. Even thofe nebula, which appear irregular, have a brighter part at fome distance from the circumference. Thefe confiderations lead our author to fuppofe, that they are grouped by regularly acting powers, which he ftyles central ones, and those more clofely clustered feem to have been long fubjected to the action of these powers, while the more irregular nebulæ appear to be actuated by the fame tendency, though the fuperior power, or more active energy of some stars have preffed laterally on the others, and impelled them from their places. This is nearly our author's outline, which he has formerly given, and has in this paper added to a little, while he has contracted other parts of it. At the end he announces his discovery of the fixth fatellite of Saturn, revolving round it in about 32 hours 48 minutes. Its orbit is faid to lie exactly in the plane of the ring. and within the orbit of what has been hitherto styled the first fatellite.

Art. XXI. An Attempt to explain a Difficulty in the Theory of Vifion, depending on the different Refrangibility of Light. By the rev. Nevil Maskelyne, D. D. F. R. S. and Aftronomer Royal.It was fuppofed by Euler that the errors of vision, arifing from different refrangibility of the rays of light were corrected in paff. ing through the eye by the proportional denfity of the different humours, without reflecting, that the refractions being made all one way, the indiftinctness must be increased rather than diminished. In order to fee what the indiftin&ness really is, Dr. Maskelyne examines the denfity of the humours, and the neceffary errors of refraction: he finds the angle of ocular aberration, from this caufe, to be about 15'; or every point in an object will appear

to

to fubtend an angle of this magnitude, which is four or five times lefs than the aberration in a good telescope produces, though it does not affect the diftinctness of the object. Distinctnefs therefore is not materially affected by the angle being so finall, yet, as even its magnitude is partly compofed of the lefs luminous rays, which are not fufficiently impreffive, if allowance be made for thefe, the angular aberration will be reduced from 15 to 3'18". To the angular aberration is owing that the fixed flars have an apparent diameter; and this disappears in a telefcope, as in the firft inftance the angle is in proportion to the diameter of the pupil, and in the fecond to the pencil of rays.

Art. XXII. Experiments and Obfervations on Electricity. By Mr. William Nicholfon; communicated by Sir Jofeph Banks, Bart. P. R. S.-Mr. Nicholfon's paper depends fo much on mifcellaneous experiments and defcriptions, which will not admit of abridgment, that we can only catch a few of the outlines, and thefe will probably lead our readers to attend more clofely to this ufeful article, which every experimental electrician will find truly valuable. The first fection is on the excitation of electricity; and our author employed the filk flap, extending from the cushion half round the cylinder. He found the filk not only prevented the return of the electricity to the cushion, as fome have fuppofed, but was a chief inftrument in the excitation; the cushion chiefly fupplying the electricity, and increafing the preffure. The filk principally acts by compenfation, in the way of a charge, fince it is always negative. The line of light, between the cylinder and cushion, in weak excitations, Mr. Nicholfon thinks is owing to the cyFinder not having been fufficiently fupplied during the rubbing, and confits of added, not returning electricity. The internal furface of the cylinder, inftead of giving out electricity, during the rubbing, attracts it; while in plates, no advantage is gained by rubbing both furfaces, except in fome particular circumftances. The following experiment, with the remark, is of too much importance to allow of an abridgement:

If a piece of filk be applied to a cylinder, by drawing down the ends, fo that it may touch half the circumference, and the cylinder be then tur..ed and excited by applying the amalgamed leather, it will become very greedy of electricity during the time it paffes under the filk. And if the entering furface of the glafs be fupplied with electricity, it will give it out at the other extremity or contact; that is to fay, if infulated con ductors be applied at the touching ends of the filk, the one will give, and the other receive, electricity until the intenfities of their oppofite ftates are as high as the power of the apparatus can bring them; and thefe ftates will be inftantly reverted by turning the cylinder in the oppofite direction.

As this difcovery promifes to be of the greateft ufe in elec

trical experiments, because it affords the means of producing either the plus or minus states in one and the fame conductor, and of inftantly repeating experiments with cither power, and without any change of pofition or adjustment of the apparatus, it evidently deferved the most minute examination.'

We fhall add alfo our author's own recapitulation of the refults of the fubfequent experiments:

1. The line of light on a cylinder departing from a fimple cufhion confifts of returning electricity; 2. the projecting part of the cushion compenfates the electricity upon the cylinder, and by diminishing its intenfity prevents its ftriking back in fuch large quantities as it would otherwife do; 3. that if there were no fuch compenfation, very little of the excited electricity would be carried off; and, 4. that the compenfation is diminished, or the intentity increafed, in an higher ratio than that of the distance of the compenfating fubftance; because if it were not, the electricity which has been carried off from an indefinitely fmall distance, would never fly back from a greater distance and form the edge of light.'

Mr. Nicholfon obferves that, in our prefent improved machines, we produce forty times the intensity which our forefathers obtained by the hand alone; and eighteen times the prefent intenfity will equal the utmost we can now condense on ftrong glass, even in the form of a charge.'-It is fome confolation to reflect, that we have ftepped over more than of

our way.

The fecond fection is on the luminous appearances of electricity, and the action of points. The forms of electrical light cannot be defcribed, except in the author's own words, and thefe depend on the plates for their elucidation. On the subject of points, our author obferves, that, as in our machines we can make a ball of 14 inch diameter act like a point, and the contrary; as our conductors are not greatly elevated and the balls propofed by fome as terminations, are fmall, the late difputes on this fubject are of little importance. He confiders it as a general law, that, in any electrified conductor, the tranfition or escape of electricity will be made chiefly from that part of the furface which is most remote from the natural state.'

The laft fection is on compensated electricity,' or the electricity which becomes latent in confequence of the equilibrium. The uncompenfated part which explodes, and is generally in proportion to the charge or the compenfated part in equilibrio, is greatly increased when a series of jars are made to charge each other. Breaking of jars is owing to this furplus, and confequently Muscovy talc, which confiits of plates, in oppofite ftates, will bear large charges without fplitting.

་་་་

Art. XXIV.

Art. XXIV. On the Production of nitrous Acid and nitrous Air. By the Rev. Ifaac Milner, B. D. F. R. S. and Prefident of Queen's College, Cambridge.-In our records, we have feen that the volatile alkali has been produced by means of the nitrous acid; but it is Mr. Milner's object to prove the converfe of the propofition, and to produce the acid by means of the alkali. Paffing the vapour of acid through iron tubes filled with turnings of iron, he produced phlogifticated air, and he thinks the feries is, firft, nitrous air; fecondly, dephlogisticated nitrous air; and then phlogisticated air. But, on paffing the dephlogisticated nitrous air through a red hot barrel, filled with turnings of iron, it changed indeed into phlogisticated air, and appeared turbid, with the evident smell of volatile alkali.

Thefe facts led our author to reverfe the experiment, and impelling alkaline air through a gun-barrel filled with manganefe, he produced nitrous air. Green vitriol calcined had the fame effect, but red lead and alum produced inflammable or hepatic air. The phlogisticated air of the volatile alkali combines with the pure air of the manganefe, while the phlogiston unites to the calces. There feems not to be enough of the pure air to form the acid, probably because its progress through the tube is too rapid.

The volume concludes with the ufual lift of donors and donations.

Afiatic Refearches; or, Tranfactions of the Society, inftituted in Bengal, for inquiring into the History and Antiquities, the Arts, Sciences, and Literature of Afia. Vol. I. 410. 21. 25. Beards. Elmly.

WE

E had long ago an opportunity of mentioning the inftitution of this Society, in our review of fir William Jones's very able and animated difcourfe addreffed to the members (Crit. Rev. vol. lix. p. 19.); and we have formed the higheft expectations from their labours. Sacred and profane history may probably be illuftrated by the productions and cuftoms of a country, which feems to have been inhabited from the earlieft ages; fcience and philofophy may be elucidated by circumftances arising from the fpot which gave them birth; arts and manufactures may be improved by the natural history of a climate congenial to the moft ufeful and ornamental productions of nature. It is not an object of the least confequence, that, by this means, we may be taught the real value of the rare pretenfions of the Bramins, and the numerous important fecrets fuppofed to be concealed under the venerable veil of the Sanferit. But we muft not anticipate the curiofity of our readers: we fall therefore turn to the volume.

The

The difcourfe prefixed we have had formerly occafion to mention: next follows the prefident's very curious and important essay on the orthography of Afiatic words in Roman letters. To afcertain the fubject more precifely, the prefident examines the formation of the fimple founds with more precision and clearness than any author we have seen, and establishes, under each found, the analogous founds of the different Afiatic letters. It is impoffible to abridge this analysis; but we may remark, that fir William Jones follows the letters, not the pronunciation, and marks the short vowels only with the usual short profodical diftinction, while the long and the accented vowels he diftinguishes, like the Italians, by an accent. His method seems very accurate and perfpicuous; and we have little doubt of its being generally adopted, and giving fome confiftency to an orthography hitherto unpleafing to the eye, and difficult to read. The poems, inserted as illustrations, are tranflated: perhaps we may be allowed to felect a part of a very beautiful one : it is the ftory of the Romeo and Juliet of the Eaft, and is a defcription of madnefs highly fublime and admirably painted.

When the prince looked at him, he beheld a wretch in bondage to the mifery of delire.

Madness had fixed her abode on his head: he was clothed, as with a vest, with the wounds of separation.

His locks flowed, like a mantle, over his body: his only fandal was the callus of his feet.

In his hair ftuck a comb of Arabian thorns: a robe of fand from the defert covered his back.

O thou, faid the prince, who haft been loft in the valley of forrow; dost thou not wish me to give thee the object of thy paffion,

To exalt thee with dignity and power, to bring Laill before thee gratifying thy foul?

No, no; anfwered he, far, far is it from my wish, that an atom should be seen together with the fun.

Speak truly, replied the prince, art thou not willing to recreate thyself on the fmooth plain of that beautiful cheek? • Or haft thou no inclination to enjoy her charms? I adjure thee by the foul of Lailì, to declare the truth!

He rejoined: O chief of men with generous hearts, a particle of duit from thy gate is a diadem on my head.

The pain of my love for Laili is fufficient for my heart: a with to enjoy her prefence thus would be injustice.

To gratify this contemptible foul of mine, a fingle ray from that bright luminary would be enough.

He fpake, and ran towards the defert, his eye weeping, and his eye-lashes raining tears.'

Art. II. Aftronomical Obfervations in Fort William, and

7

between