The Disparition of Saturn's Ring, Observed by Joseph Varelaz, Lieutenant of the Royal Navy of the King of Spain, and Professor of Mathematics, in the Academy of Guard-Marine at Cadiz. In a Letter to Dr. Morton

XIII. The Disparition of Saturn's Ring, observed by Joseph Varelaz, Lieutenant of the Royal Navy of the King of Spain, and Professor of Mathematics, in the Academy of Guard-Marine at Cadiz. In a Letter to Dr. Morton. Translated from the Spanish. Cadiz, October 12, 1773. SIR, Redde, Dec. 23, 1773. It has been my luck to observe the celebrated phenomenon of the round phase of Saturn, which was so much recommended to Astronomers, in the Gazette of France of July 23. From the 24th of September to the 4th of October, I saw, clearly and distinctly the two ansæ of the ring; but with this particular circumstance, that the occidental ansa appeared more strongly illu- --- Cadiz, 12 de Octubre de 1773. Muy Senor mio, ACABO de observar el celebre fenomeno de la fase redonda de Saturno, que tanto se recomendó á los Astronomos en la Gazeta de Francia de 23 de Julio de este ano. Desde el dia 24 de Septiembre hasta el 4 de Octubre he visto clara y distintamente las dos ansas del anillo, aunque con la particularidad de que el ansa occidental parecia mas bien iluminada que illuminated than the oriental. The atmosphere was thicker on the 5th, and I could only see the occidental. The 6th, I thought I could discern some faint remains of the ring; but that might be a deception of my sight, because the atmosphere remained very thick, and the planet could not be seen well terminated. On the 7th, the atmosphere being more transparent, and the heavens clearer than I have ever seen them, I observed the total disappearance of the ring; and, having repeated the same observation the following day, I was convinced that this famous phenomenon took place the 6th day of the month, in which determination I have all the exactness, which can be expected in observations of this kind. The most striking circumstances of this phenomenon were the following; 1. The occidental ansa constantly appeared more bright than the oriental. 2. On the disc of the planet, one could clearly distinguish the line of the shadow projected from the que la oriental. El dia 5 estaba la atmosfera algo densa, y solo pude distinguir el ansa occidental. El dia 6 me pareció haber percivido algun vislumbre del anillo, pero tal vez seria una ilusion de mi vista, porque estaba la atmosfera sumamente densa, y no se podia ver el planeta bien terminado. El dia 7, con la atmosfera mui limpia y el cielo mas claro que he visto jamas, observé la total desaparicion del anillo, y habiendo repetido la misma observacion al dia siguiente, me aseguré en que esta celebre phase se havia verificado el dia 6 de este mes, en cuya determinacion hay toda aquella exactitud de que son susceptibles estas observaciones. Las particularidades mas notables de este fenomeno han sido las siguientes. 1. El ansa occidental parecia siempre mas bien iluminada que la oriental. 2. En el disco del planeta se distinguia claramente la linea de la sombra que pro- the thickness of the ring. 3. On the extremities of this, some luminous points were perceived, which reflected the light more strongly than the others. 4. I did not observe a sensible variation in the apparent diameter of the ring. I made use, for this observation, of a five-feet reflector of Mr. Short, of another of four of Mr. Nairne, and of an excellent acromatic telescope of Mr. Dollond, to which I applied one of the strongest and brightest magnifiers. I assure you, Sir, that I have given to this observation all the attention, which the importance of the matter required; and this joined to three others, form a set of observations on the planets, the occultations of fixed stars by the moon, and the Satellites of Jupiter. I shall send you a copy of the whole, if you think proper to present them to the Royal Society, and will accept of my correspondence. Don yecía el espesor del anillo. 3. En los extremos de este se percibían unos puntos luminosos que reflejaban la luz con más viveza que los otros. 4. En el diámetro aparente del anillo no hubo una variación sensible. Me serví para esta observación de un telescopio de 5 pies de Mr. Short, de otro de 4 de Mr. Nairne, y de un excelente anteojos acromático de Mr. Dollond, al cual apliqué uno de los tubos más fuertes y claros. Aseguro a vm. haber hecho esta observación con toda la prontitud, que pide la importancia de la materia, y con la misma tre formado un Quaderno de observaciones sobre los planetas, occultaciones de estrellas fijas por la Luna, y Satélites de Jupiter. De todo embiaré a vm. una copia, si gustare presentarla a la Sociedad Real, y admitir mi correspondencia. Dn. Don Vincent Tofino Captain of a frigate in the King's fleet, and Director of the Academy of the Guarde-marines, has had a great share in these observations. He is no less desirous, than myself, that they should be communicated to the Royal Society: for which purpose, I request an answer from you, which you will please to address to, SIR, Your most humble obedient servant, JOSEPH VARELAZ, Lieutenant in the Royal Navy, and Professor of Mathematicks in the Academy of Guarde Marines. Dn. Vincente Tofino, Capitan de Fragata de la Rl. Armada, y Director de la Academia de Guardias-Marinas, ha tenido mucha parte en estas observaciones. Desear como yo comunicarlas á la Sociedad Real, á cuyo fin suplico á vm. que me responda, y que me mande como á Su mas rendido y obediente servidor, JOSEF VARELAZ. Teniente de Navio de la Real Armada y Profesor de Mathemathicas en la Academia de Guardias Marinas.