A 11^11 st 30, 1877] 



NA TURE 



36: 



tenacious resistance of the great majorily of the Spanish pro- 

 fessors. 



Some champions of modern ideas are happily not ^vantini; in 

 Spain. Among them is one of the most distinguished members 

 of the Madrid Observatory, Sr. Jimenez, who has written an 

 interesting volume on the theory of numbers, which obtained a 

 prize from the -Spanish Academy of Science. Sr. Jimenez 

 began to publish a few years ago a theory of light in com- 

 pliance with the most authorised physico-mathematical doctrints. 

 A man of immense and varied intellect, as a dramatic poet, as 

 an engineer, as a mathematician and economist, and one of the 

 principal men of the revolution, Sr. Echegaray has done much 

 to popularise the modern theories of physics, by a volume 'dedi- 

 cated to the General Public, and also by his elementary treatise 

 on thermo-dynamics. lie is now publishing some studies on light 

 in a scientific review, which are chiefly intended to extend these 

 studies in our scientific circles. Dr. Vicuna, Professor of Mathe- 

 matical Physics at the M.adrid University, endeavours to do the 

 same by his teaching, and by means of the articles and memoirs 

 which he publishes from time to time. Of these may be men- 

 tioned his theory and calculation of steam-engines in accordance 

 with thermo-dynamics. 



The scientific instruction which is given to the young men who 

 attended the upper school at the Observatory of Marino, at Saii 

 Fernando, near Cadiz, is much commended. Every day foreign 

 books are more universally read, translated, and understood, the 

 most popular being thofe by Tyndall. Prof. Karreda, Felin, 

 Ramos, v. Chamorro are great advocates of modern science. 

 Sr. Escrig y Mieg, the professor at the Institute at Guadalajara, 

 has set up some interesting scientific apparatus there, and has 

 introduced in the pneumatic machine an improvement wliich 

 reduces the injurious space. The barometer constructed by .Sr. 

 Torres, the inventor of probably the most accurate barometer 

 known in European meteorology, merits special mention. It is 

 much to lie regretted that owing to special circumstances, his 

 instrument could not figure at the interesting exhibition at 

 South Kensington. 



At the Free Institution, lately established for teaching at 

 Madrid, by private enterprise, which the readers of Nature 

 have already seen referred to in jour columns, there is a class of 

 experimental physics, according to the Litest development of this 

 science. On the evening of January 28, a series of public 

 lectures were begun, with the object of popularising science in 

 Spain. Dr. Simarro, a young professor at this institution, gave 

 the first lecture on light, and repeated some of Tyndall's most 

 remarkable experiments. 



Most of these efforts are, however, still limited to the attempt 

 to spread in Spain a knowledge of the actual state of physical 

 science from other countries which are in a more advanced con- 

 dition, rather than to contribute to general culture works of 

 original investigation. The interesting studies of Prof. Serrano 

 Faligate, on general and biological physics, some of which have 

 been noticed by English reviewers, are almost the only works on 

 the subject which can Dc mentioned of importance. It is indeed 

 to be hoped this will no longer be the case when these studies 

 are more generally developed, and act as a stimulant to the 

 genius of the Spanish people. 



Madrid Francisco Ginez de los Rios 



OUR ASTRONOMICAL COLUMN 

 The Rotation of Saturn. — In N.^ture (vol. .w. 

 p. 243), reference was made to the discovery by Prof. 

 Asaph Hall of a small, well-defined, very white spot upon 

 the disc of Saturn just below the ring, and to observations 

 which were in progress to ascertain, by means of it, the 

 period of the rotation of the planet upon its axis. Prof. 

 Hall succeeded in following up this spot which was from 

 2" to 3" in diameter until January 2, when the weather 

 having become unfavourable, the planet low, and the spot 

 faint and indistinct, observations were discontinued. 

 From a thorough discussion of the observations at 

 Washington and elsewhere in the United States, Prof. 

 Hall finds for the mean time of the rotation of Saturn — 

 loh. i4ni. 23s'S ± 2;'3o. 

 It has been necessary to assume that the spot had no 

 proper motion upon the surface of the planet, which ii a 

 point on which the observations throw no light. 



On the first detection of this spot on December 7, with 



the view to secure assistance from other observers in 

 noting its central passages on the disc, an ephemeris was 

 circulated from Washington, in preparing which the time 

 of rotation was taken at loh. 29m. i6'Ss., given, as Prof. 

 Hall remarks, " in nearly all the modern text-books as Sir 

 W. Herschel's last and most accurate determination ; " 

 notwithstanding this it appears certain that Sir W. 

 Herschel never assigned this period, and its adoption in 

 the Washington epheineris was so far unfortunate as it 

 may have rather hindered than assisted observations ; 

 indeed " through this mistake several observers failed 

 to see the spot." 



It is very probable that Prof. Hall has suggested the 

 real cause of the introduction of this erroneous value for 

 the time of Saturn's rotation into so many of the so-called 

 " text-books," the compilers of which rarely concern 

 themselves with references to original authorities, and 

 yet in this case the erroneous value has been given by 

 writers, whom it might well be supposed it was safe to 

 follow. In the Exposition dii Sysihjie dii Monde, the 

 first edition'of which appeared in An. IV. of the French 

 republican era, Laplace says that Saturn rotates in o'428, 

 and the ring in o'437, these figures being decimals of a day ; 

 they correspond to loh. i6m. i9'2s. and loh. 29m. i6'Ss., 

 the former expresses therefore the Herschelian period of 

 rotation (loh. i6m. o'4s.) to the nearest decimal in the 

 third place, and the latter is the \alue for rotation of 

 Saturn given in so many astronomical works. Hence 

 Prof. Hall thinks that some one early in the century 

 copied and converted the wrong number from Laplace 

 and " the book-makers h.ave faithfully copied this 

 mistake." 



Hansen in his "Allgemeine Uebersicht des Sonnen- 

 systems " gives loh. 29m. 17s. for time of rotation both of 

 Saturn and his ring ; Madler, " LTeber die Weltstellung 

 der Korper unsers Sonnensystems," has loh. i6m. for the 

 globe and loh. 29m. 17s. for the ring, but in the early 

 editions of his treatise on Astronomy (as in that of 1S49, 

 pp. 251 and 254) he assigns loh. 29m. 17s. for the globe, 

 and loh. 32m., after Herschel, for the ling, adding 

 " wahrscheinlich ist sie der des Saturn selbst gleich und 

 beide sind etwa loh. 30m. in runder Zahl." Sir John 

 Herschel, in the first edition of his Treatise on astronomy 

 in Lardner's " Cabinet Cyclopjedia" published in 1833, 

 gives I oh. 29m. 17 s. both for Saturn and the ring, and he 

 probably followed Daily's " .\stronomical Tables and 

 Formula;" which appeared in 1S27, and where we find at 

 pp. 39 and 59 the same period loh. 29in. i6'S5. assigned 

 lor both rotations, and Baily expressly states that "the 

 elements of the system are taken for the most part from 

 the Systhnc du Monde o( M. Laplace (fifth edition, 1S24), 

 so that it is possibly to this work, which was one of 

 general reference for many years, that the original over- 

 sight suggested by Prof. Hall is to be traced. Sir W. 

 Herschel in the Pltilosophical Transactions, 1790, p. 480, 

 states that his observations of lucid spots upon the ring, 

 supposing them to adhere to it, would be explained 

 by "admitting a revolution of the ring itself in 

 loh. 32m. I5'4s., and \n the volume for 1794, p. 28, he 

 finds for the rotation of the globe of Saturn, loh. i6m. 

 o'44s., which are the only values th.at bear his authority. 



Prof. Asaph Hall's value must now be taken as un- 

 doubtedly a very close approximation to the true period 

 in which Saturn rotates. According to it, the planet's 

 year consists of 25.217 Saturnian days. To the rarity of 

 spots upon the disc of so small and well-defined a 

 character as that which has been recently observed to 

 such useful purpose at Washington, is perhaps to be 

 mainly attributed the want of an e.irlier reliable deter- 

 mination of the rotation period in confirmation of Sir W. 

 Herschel's, made upwards of eighty years previously. 



The Comet of 1812. — In anticipation of the return of 

 this comet to perihelion within the next few years. Prof. 

 Winnecke has published ephemerides to facilitate its 



