the rows; the result proved highly in favour of the consolidating system; that part which had been trodden was not in the least mildewed; the untrodden was very much so. The species of smut called in this county powderbrand or blind ears, though certainly unsightly, is not so injurious as it appears: I do not think it infectious; though I have taken some pains to inoculate good seed with the powder. The first heavy rain generally washes it off the stem on which it was produced. It is more prevalent in white than in red wheat; but it is likewise frequently found both in barley and oats: careful washing in two or three waters will prevent the spread of the disease. I have been induced to send you the above, in the hope, as before observed, that it may lead to discussion and practical observation amongst such of your readers as may have a taste for agricultural pursuits; and believe me to remain, Gentlemen, Bungay, Oct. 22, 1822. Your most obedient humble servant, LXX. Description of Hemipodius nivosus; a new Bird from Africa. By WILLIAM SWAINSON, Esq. F.R.S. and L.S. M.W.S. &c.* THE singular birds forming the genus Hemipodius, are inha bitants of the African and Asiatic continent. Their usual size is so remarkably small, that they may be considered the pygmies of the gallinaceous tribe; between which, and the Gralle they appear to hold an intermediate situation. Like the Couriers (Cursorius) they are destitute of the hind toe, and have the same lengthened legs; but the bill is straight instead of curved, and the nostrils furnished with a convex horny membrane, instead of a depressed naked furrow. Little is known of their manners or œconomy. They inhabit (according to Temminck) the confines of sandy deserts, and the arid tracts of Africa and India, appearing to migrate, two species being known to visit the southern parts of Spain. Their flight is said to be amazingly rapid. Nine species have been described with much accuracy by Professor Temminck in his valuable work on the Gallinacea. Respecting the generic appellation of these birds, much opposition has been evinced by those authors who have noticed them; for no less than eight different generic names have been proposed; among these the priority, I believe, belongs to Brisson, who distinguished them by the name of Coturnix * Communicated by the Author. Y y Vol. 60. No. 295. Nov. 1822. in in his Ornithologia printed in 1763. This name, therefore, should, I think, have been adopted by modern writers; but as Professor Temminck has given such a full account of the species, and proposed another so very expressive as Hemipodius, I think much confusion will be saved by continuing it; particu larly as this has already been done by Cuvier; although Dr. Leach, in transcribing Temminck's descriptions, has adopted the unmeaning one of Turnix as a Latin designation. HEMIPODIUS NIVOSUS.-White-spotted Turnix. SPEC.CHAR.-H. supra ferrugineo varius; mento albescente; jugulo pectoreque pallidè ferrugineis, maculis albis nitidis ornatis; corpore albo; uropygio caudæque tectricibus superioribus rufis, immaculatis. Above varied with ferruginous; chin whitish; throat and breast pale ferruginous with white shining spots; body white; rump and upper tail-covers rufous, unspotted. DESCRIPTION.-Size of a lark. Total length about five inches. Bill dusky, half an inch from the angle of the mouth to the tip; compressed the whole length, but not so much elevated at the base as about the middle, where it slightly rises, and the culmine (or dorsal ridge) forms a gentle curve to the tip, which is not, however, either bent down or notched: the under mandible is straight. Nostrils large, placed in a groove, which reaches to more than half the length of the bill, and there terminates in a point; it is defended above by a protuberant, convex, horny covering, which nearly reaches to the end of the groove; the nasal aperture is by a lengthened marginal slit at the base of the protuberance, and close to the margin of the bill. Upper plumage reddish brown, striped with whitish fawn colour, and freckled transversely with blackish . on the back and scapulary feathers; this whitish colour borders the sides of each feather, and has an internal narrow edging of blackish brown, while the shafts are crossed by short blackish lines: the sides of the head are not spotted, but an obscure whitish band seems to pass both above and below the ears; the back, rump and upper tail-covers are rufous, and likewise unspotted; the lower half of all the wing-covers are white, the upper half ferruginous with white spots and margins. The Wings are rounded, the three outer quills progressively longer; the fourth very short, and the fifth surpassing in length all the others*: the lesser quills (nearest the shoulder) are formed like the scapulars and are remarkably long, far exceeding in length all the greater quills: the three exter* A singular formation, which I have not the opportunity at present of comparing with other birds of this genus. nal nal quills are white, with the tips and base black; the remainder, together with the lesser quills, are black with white tips; the Tail is nearly hid by its covers, and just exceeds the length of the wings when closed; the feathers are fasciculated, very short, and fawn-coloured, transversely marked with waved bands of dark ferruginous, edged with black. Spurious quills black. Of the under plumage, the chin is nearly white, changing gradually to ferruginous; each feather on the neck and breast being spotted with white, which spots possess the singularity of being in some lights almost invisible, but in others of a pure shining snowy whiteness; from the breast to the vent all the plumage is white. Legs yellow, one inch and a quarter from the naked part of the thigh to the heel; all the toes are cleft to the base, and the inner one smallest. The birds of this genus have such a general resemblance in the markings of their variegated plumage, that a minuteness of description, although objectionable on most occasions, here becomes absolutely necessary. This description was framed from a specimen belonging to Mr. Leadbeater, who received it from Africa; another I have since seen in the well-known Museum of Mr. Brookes. LXXI. A Letter from JOHN POND, Esq. Astronomer Royal, to Sir HUMPHRY DAVY, Bart. President of the Royal Society, relative to a Derangement in the Mural Circle at the Royal Observatory*. THE MY DEAR SIR, HE interest which the Royal Society has always taken in every thing relating to this Observatory, and to which may be attributed its present prosperous condition, will, I trust, render unnecessary any apology for this communication. I wish to make known to astronomers, as soon as possible, a derangement that has for some time past existed in the mural circle, and of which I have not, till lately, been able to ascertain the cause with certainty. This derangement began, I believe, about the autumn of the year 1819; the position of the telescope was then changed; and from that time the error has been gradually increasing till last summer, when the cause was distinctly ascertained, and the proper remedy applied. In the Preface to the Greenwich Observations for the year 1820, now printing, I shall have an opportunity of stating the * From the Philosophical Transactions, Part I. for 1822. Y y 2 amount ap amount of this error, and the correction which should be plied to the observations made within the two last years. At present it will be sufficient to mention, in as few words as possible, the cause of this error. Those who are acquainted with the construction of the Greenwich Mural Circle, are aware, that though the telescope may be applied to every part of the circle, yet, when fixed for observation, the principle of the instrument requires that the tube, especially at its extremities, should be so firmly fixed to the circle as to form one piece with it: to accomplish this, connecting braces are attached at each end of the telescope. It now appears that these braces have, in progres of time, become insecure, owing to the screws which fastened them having given way. The effect of this will be, to permit the ends to bend from the centre instead of retaining, as they ought to do, an invariable position with respect to the circle. Under these circumstances, when the telescope is directed to the zenith, the position may be considered as free from error; but when the instrument is moved either towards the north or south horizon, should either extremity bend more than the other, an error will take place, and will increase from the zenith towards the horizon, but in what exact proportion, remains to be determined by future observations. The cause of this error being thus ascertained, Mr. Troughton has applied additional braces to connect the telescope with the circle, sufficiently strong, I should conceive, to prevent the possibility of such an accident for the future. This alteration has already produced such an improvement in the observations, as prove sufficiently that the source of error has not been mistaken. Of the published Observations, only those made in the three last months of the year 1819 are affected by this error, and that in so very small a degree, as must have entirely escaped notice, had it not afterwards increased. During the year 1820 the error increased; but did not, I believe, in the distance from the pole to the equator amount to two seconds; at altitudes lower than Sirius, and at the altitude of the sun at the winter solstice, the error may have been greater than two seconds, but did not exceed four. But after the month of February 1821, the error rapidly increased; and this ultimately led to a discovery of the cause. My present object in this letter, is simply to state these circumstances to the Society. I shall defer a more detailed account of the nature of this derangement, and of its effects, till I shall be enabled, by a sufficient number of observations made. with the instrument in its improved state, to ascertain, with some some degree of certainty, at what period the derangement took place, and what corrections are required to be applied, till the instrument was restored to its perfect state. I have the honour to be, my dear sir, With the highest regard, Your most obedient humble servant, Royal Observatory, Nov. 21, 1821. JOHN POND. LXXII. On the Subsidence of Aqueous Vapour; and its Repose on the Beds of Rivers. By JOHN MURRAY, F.L.S. M.W.S. &c. &c. To the Editors of the Philosophical Magazine and Journal. GENTLEMEN,-THE President of the Royal Society has ingeniously ascribed the formation of mists in particular situations, to the superior temperature maintained by currents of water from below, these supplanting the superficial wave and supplying its place, when cooled down by radiation. This movement and interchange would continue so long as any part of the mass remained above 45°. On this principle the air incumbent on the bosom of the river would, having its loss by radiation thus compensated for, remain at a higher temperature than that reposing on the banks of the river which can have no such compensation. The cooler atmosphere of the latter would therefore move towards the former, and mingling with it, mist would be formed. Now, though the currency of a rapid river, as the Rhone for instance, might, prima facie, seem to disturb the rise and fall from below and above, still it must be confessed that the view sustained, is every way worthy of its distinguished author. My own experiments on the Seine and the Po seemed not to harmonize with these views; but the thermometer might be in fault, and I was willing to cede the point. On the 3d instant a fine opportunity was afforded me for ascertaining the question with exactness and precision. The numerous repetitions of the experiments, and the great extent of surface examined thermometrically, with the extreme delicacy of the instrument, enable me to submit the results to you with unusual confidence. Rain obtained in the early part of the day, and the sky was dark and lowering. The horizontality of the clouds, with their parallelism in the distant sky, seemed to indicate the prevalence of electric influence. Toward the afternoon, mist formed |