170 



KNOWLEDGE. 



[July 1, 1897. 



is, as we shall presently see, the theatre of vast and almost 

 continual chanf,'es. . ,, . 



Owing to its remarkable dimensions the Syrtis Major was 

 the first markmg ever detected by man on Mars. The 

 honour of this discovery belongs to Christian Huyghens, 

 the distinguished discoverer of Saturn's ring, and ingenious 

 deviser of the first pendulum clock. The accompanying 

 woodcut (Fig. 1) is a facsimile 

 reproduction, after M. Terby, 

 of Louvain (Belgium),* of 

 Huyghens' original sketch, dated 

 1659, November 28th, 7 o'clock 

 P.M. By following the motion of 

 this spot, Huyghens concluded 

 that the rotation of Mars on its 

 axis ought to take place in about 

 twenty-four hours. 



For one hundred and twenty 

 years following Huyghens' dis- 

 covery, areography made almost 

 no progress whatever ; but in the 

 years 1777, 1779, and 1781, Sir 

 William Herschel made a fine series of drawings of Mars, 

 which, in reality, constitute a very marked advance of our 

 knowledge of the planet's surface. The Hourglass Sea was 

 drawn with its true outline, while Herschel's views show 

 at the same time that great inlet which was later named after 

 Nasmy th, and now is more commonly known as the Nilosy rtis. 

 A careful examination of Herschel's drawings excites the 

 suspicion that a notable change may have taken place 

 on the western shores of the Syrtis, towards the southern 

 extremity of Schiaparelli's Aeria, where Banks Cape or 

 Hammonis Cornu was probably considerably more con- 

 spicuous in 1781 than it at present is. Schroeter's drawings, 

 however, made twenty years later, give but little support to 

 this view. 



The observations of Beer and Maedler (1830-18411 do 

 not increase our knowledge of this part of the planet. 



Fig. 1. — The Hourglass 

 Sea on Mars, as drawn by 

 Huyghens two hundred and 

 thirty-eight years ago. 



very fine view of the Hourglass Sea, with its northern mlet, 

 the Nilosyrtis, forming, where it curves westward, a round 

 dark spot, to which Schiaparelli gave the name of Coloe 

 Palus in 1879. The white region at the top of the drawing 

 is not the south polar snowcap, but rather the island of 

 Hellas (Lockyer Land), belonging to that peculiar class of 

 "lands" on Mars which appear of a dull, ruddy hue 

 when near the centre of the disc, but which increase in 

 brightness in the vicinity of the limb, appearing occasion- 

 ally in this position as bright as the polar snowcaps them- 



In 1858 Secchi undertook a series of observations of 

 Mars which led to the discovery of a considerable number 

 of what are now so familiar 

 to us as "canals." We 

 choose from Secchi's 

 collection his drawing of 

 .June 15th, 1858 (Fig. 3), 

 in which our sea is likened 

 to a scorpion — a certainly 

 not unhappy comparison. 



The year 1862 will re- 

 main for ever memorable 

 in the history of areo- 

 graphy by the excellent 

 observations of Mr. 

 Lockyer, who gave us the 

 first really truthful repre- 

 sentation of the planet. 

 Mars was then at one of 

 its perihelia oppositions, 



consequently almost at its minimum distance from the 

 earth, but unfortunately unfavourably situated to European 

 astronomers ou account of its great southerly declination. 

 Lockyer's drawings of the Hourglass Sea region, of which 

 Fig. 4 is one of the best, estabUsh that in 1862 the coast 



Fig. 2.— The Hourglass Sea on 1856, Ain-il 20th. (W. de la Rue.) 



In 1856 Warren de la Rue made some very interesting 

 drawings of Mars, one of which, dated April 20th, 1856 

 (Fig. 2),t is particularly remarkable. Here we have a 



* ArcoqrapUe (Acadtmie de Belflitjiie, 1875, p, 8). . , ■ 



t We have extracted all the nine woodcuts accompanying this 



paper from M. Flammarion's admirable monograph, " La Planete 



Mars." (Paris : Gauthier Villars, 1892.) 



Fig. 3. — The Hourglass Sea on 

 1858, June 15th. (Secchi.) 



Fig. 4.— The Hourglass Sej, on 18G2, October .3rd. (Lockyer.) 



of Libya and the eastern shores of the Hourglass Sea were 

 very much like what they were in 1877. Libya seemed 

 somewhat dusky to the south-west, while some very con- 

 spicuous features on its surface are the three shadings 

 extending from .r to '/. These constitute the first proper 

 view of the round dark spot called the Main Sea, and 

 which Schiaparelli has christened by the name of Mojns 

 Lacus. It is possible that this " lake " was triple in 1862, 



