NATURAL PHILOSOPHY. 179 



stereoscope showed the moon as a sphere. Our readers will under- 

 stand how such a remarkable result has been obtained, by considering 

 that binocular pictures of a statue may be taken with a fixed camera, 

 by making it move round its axis through the binocular angle, and 

 taking the two pictures in succession. Now, though the moon has not 

 a motion of rotation relative to the earth, yet it has a libratory motion 

 through an arc of twenty-one degrees, which is more than sufficient to 

 give a right and left eye picture of it ; and Mr. De La Rue, having 

 taken photographs of her at two epochs of maximum libration, has 

 succeeded in producing the wonderful result of exhibiting the moon 

 in the stereoscope with all the roundness of a sphere. As the stereo- 

 scope has the remarkable property of exhibiting effects which are not 

 seen in the single picture, several of the radiating lines in the single 

 moon's disc have been found by Mr. De La Rue to be furrows, one of 

 which, extending from Tycho, is fifty miles wide. 



Mr. De La Rue has also taken photographs of Jupiter, which 

 " show the configuration of the belts sufficiently well to afford the 

 means of producing stereoscopic pictures." In the space of twenty- 

 six minutes, the planet will have rotated through the binocular angle. 

 Mars will rotate through the same angle in sixty-nine minutes ; and 

 as the markings are very distinct, Mr. De La Rue hopes to obtain 

 stereoscopic views of that planet. From the opening and closing of 

 Saturn's ring, Mr. De La Rue expects to obtain a stereoscopic picture 

 of him, having already obtained an approximate result from the union 

 of two drawings which he had made in November, 1852, and March, 

 1856. 



In the photographs of the sun obtained by Mr. De La Rue, the 

 faculse and the spots, with their penumbras, are finely seen. When 

 the collodion is over-exposed, the faculae first disappear, then the 

 penumbrae, and then the spots. The spots and faculag bear a magni- 

 fying power, and show details not visible to the unassisted eye. Good 

 binocular pictures, taken at the interval of a day, when united, show 

 the sun as a sphere in the stereoscope. 



In 1858, Father Secchi, of Rome, sent to the Academy of Sciences, 

 in Paris, a photograph of the moon, eight inches in diameter, in the 

 seventh day of her age, having taken her picture in various other 

 phases. He obtained, also, a photograph of Jupiter, which showed 

 his belts very distinctly, and also traces of some of his satellites. It 

 took twice as long time as the moon the day after the full, so that the 

 force of light (actinic rays only) in Jupiter is greater than that of 

 the moon, seeing that their distances from the sun are as five to ten. 

 Father Secchi sent also to the Academy, in the same year, a photo- 

 graphic atlas, in which the moon's diameter was eight inches, from 

 negatives about two inches in diameter, enlarged with a great solar 

 microscope. He had obtained, also, an excellent photograph of Sat- 

 urn, which, though only the twenty-fifth of an inch in diameter, not 

 only showed the black spaces between the planet and the ring, but 

 the shadow of the planet on the ring. It bore to be magnified to a 

 diameter of one and a half or two inches, and established two remark- 

 able facts : first, that the planet was " more sombre " than the ring ; 

 and, second, that the light of the planet (the actinic rays only) was 

 stronger in proportion than that of the moon ; for the full moon was 



