BEING THE ANNUAL HALF-VOLUME OF THE MEMOIRS AND FROCEEDINGS

OF THE ROYAL ASTRONOMICAL SOCIETY.

LONDON:

PRINTED BY

GEORGE BARCLAY, CASTLE STREET, LEICESTER SQUARE.

1859.

ROYAL ASTRONOMICAL SOCIETY.

VOL. XIX.

November 12, 1858.

No. I.

Dr. LEE, V.P., in the Chair..

Cyril C. Jackson, Esq., Grand Cairo; and

John Nicholl, Esq., LL.D., Professor of Astronomy in the

University of Glasgow,

were balloted for and duly elected Fellows of the Society.

On the Distribution of the Solar Spots in Latitude since the Beginning of the Year 1854; with a Map. By R. C. Carrington, Esq.

I had fully hoped that by the time when the Society would meet again in the month of November I should have been able to present the members with a tolerably complete discussion of the series of solar spot observations which I have now kept up at Redhill for nearly five years; but a family loss by the hand of death has for the last three months deprived me of the leisure I had counted on, and compels me to confine the present paper to the publication of a single feature which the assembling and comparison of results has brought to light. It will be found to be another and instructive instance of the regular irregularity and the irregular regularity which, in the present state of our knowledge, appear to characterise the solar phe

nomena.

In the briefest form of statement, the result is, that throughout the two years preceding the minimum of frequency in February 1856, the spots were confined to an equatoreal belt, and in no instance passed the limits of 20° of latitude N. or S.; and that shortly after this epoch, whether connected with it or not, this equatoreal series appears to have become extinct, and in seeming contradiction to the precept, Natura non agit per saltum, two new belts of disturbance abruptly commenced, the limits of which in both hemispheres may be

roughly set at between 20° and 40°, with exceptions in favour of the old equatoreal region. The tendency at the present time appears to be to contraction of the parallels.

The method of reduction employed having already been explained and sufficiently illustrated in these pages, it is only necessary on this occasion to explain the arrangement of the accompanying map.

In a mean solar day the sun rotates through an angle of 14° 11′ very nearly, and the heliographical longitudes of spots, as compared with that of the centre of the disk, increase by the synodic quantity corresponding. If an observer plots down on each day the positions reduced to noon of the spots recorded on the 180° viewed, and lays the successive sheets so as to superpose the positions of the same spot, his plotting sheets will advance daily to the left by 13° 12′ nearly. And if he then agrees to adopt one figure of a spot as typical, to be laid down on a single continuous sheet, he will obtain a result such as I have deduced by computation (with the exception that for convenience my map is reversed left for right), and such as might be supposed to be produced by imagining the sun to be the central cylinder of one of Applegarth's printing-machines. In this state the graphical result would be of too extreme dimensions in length for the eye to take it in as a whole; and, accordingly, in the map lithographed the scale in longitude is reduced in the proportion of 72 to 1, as compared with the scale in latitude, and the delineations of spots compressed to mere vertical lines. The uncertainty of the exact period of rotation affects the result only in this way, that if the true period be somewhat longer than that adopted, the vertical lines which indicate the commencement of successive rotations, should be drawn somewhat wider apart, and vice versâ; a matter of no importance, obviously, for our present purpose.

The variation of the limiting parallels being established, the inquirer next desires to turn back to such past records as may throw light on their changes and their relation to epochs. In this respect I would call attention to a short, but very condensed and important paper, communicated to me by Dr. C. H. F. Peters, formerly of Naples, and lately of Albany, and published, I believe,* by the American Association for the Advancement of Science. Dr. Peters observed the sun with an object and purpose very similar to my own, from September 1845 to October 1846 inclusive, and obtained 813 places of 286 spots, which he subsequently reduced with a skill and exactness in which I place great confidence. He has given a plate exhibiting the gross distribution in latitude during the period of his labours, in which I find the limits laid down as 40° N. and 30° S. with a desolate region from 8° N. to 5° S., and with, on the whole, a preponderance of action in the north

* I have by me only the sheets of the volume containing this particular paper, sent by post.