EDITOR'S TABLE. 



745 



thetic cooperation. "When the differ- 

 ent races and nations come into rela- 

 tion in the sphere of politics or religion, 

 antagonisms, discords, jealousies, and 

 hate, are almost inevitably engendered. 

 But, when these are put aside, or kept 

 out of view, and the object to be at- 

 tained is simply to extend the knowl- 

 edge of Nature, the better elements of 

 humanity begin to be recognized and 

 asserted. As a striking illustration of 

 this, we have the curious fact that, with 

 reference to the approaching eclipse, it 

 is not the Europeans, but the " King 

 of Siam who has taken the initiative 

 in inviting astronomers to his domin- 

 ions, and providing for their entertain- 

 ment while there." On the 9th of last 

 October, his Siamese majesty, through 

 his private secretary, Bhashakarawang- 

 se, extended this courtesy to the Royal 

 Astronomical and Boyal Societies, and 

 to any astronomers they might accredit 

 to him for the purpose of utilizing the 

 coming opportunity. The English Gov- 

 ernment sends out an expedition ; and 

 an expedition by the French Govern- 

 ment goes under the control of !M. 

 Janssen. Dr. Hermann Vogel, the emi- 

 nent Berlin astronomer and photogra- 

 pher, will join the expedition of Jans- 

 sen at Singapore, and Prof. Tachani 

 will represent the Italian observers. 



An intelligent writer in the Herald, 

 in the full account which he gives of 

 the preparations for the coming eclipse, 

 thus describes an instrument which has 

 been recently constructed to facilitate 

 observation, and from the use of which 

 much aid is to be expected : 



" The siderostat was devised to enable 

 the observer to escape the inconvenience 

 and often the impossibility of changing his 

 position to follow the eye-piece of his tele- 

 scope, when turned upon the moving sun or 

 star. With the best telescopic mountings 

 and arrangements which have heretofore 

 been employed, the observer is put fre- 

 quently in the most uncomfortable posi- 

 tions, and his work subjected to those er- 

 rors irreparable from the nervous handling 

 of his glasses at the exciting and critical 

 moment of the eclipse. The ingenious sci- 



entist, Foucault, the perfecter of the side- 

 rostat, aimed to give the equatorial the power 

 of making the entire heavens pass before the 

 observer without his having to disturb him- 

 self or to displace the instrument. The 

 siderostat, as arranged by him, is, therefore, 

 a telescope fixed horizontally in an invari- 

 able position, before which a plane mirror 

 brings successively the various points of the 

 sky. The whole rests on a brass stand, sup- 

 ported by three screws, with two levels and 

 a regulating azimuth movement. The plane 

 mirror is carried by an horizontal axis on the 

 top of two vertical supports, which revolve 

 round a centre, the movement being per- 

 fectly effected by small wheels at thd foot 

 of the supports. By the employment of the 

 isochronous regulator of Foucault, placed at 

 the foot of the instrument, a motion sensibly 

 equal to the diurnal motion is communicated 

 to the plane mirror, so that the heavenly 

 bodies maintain invariable positions in the 

 field of the horizontal telescope, in front of 

 the apparatus directed toward the mirror. 

 This clock-movement, which has been ap- 

 plied to equatorials, is perfectly regular, 

 and won for its inventor the grand prize iu 

 the mechanical arts at the Universal Exhi- 

 bition of 1867. The apparatus gives perfect 

 steadiness in experiments for measuring the 

 position of spectrum lines and of the dis- 

 placement of the lines by means of large 

 fixed spectroscopes. Its adaptability has 

 been tested during the recent photographic 

 experiments in connection with the transit 

 of Venus, and with the greatest ease it com- 

 bines with the observing telescope the ap- 

 paratus necessary for the work of celestial 

 photography for photometric researches. 

 The complete instrument, telescope and 

 siderostat, placed in the plane of the me- 

 ridian, may also be regarded as a meridian 

 instrument, so that it is, perhaps, the most 

 powerful weapon of modern astronomy ; 

 and, when desired, spectroscopes and pho- 

 tographic apparatus can be attached to the 

 eye-piece of the telescope, of a size even 

 larger than the telescope itself." 



THE LITERATURE OF EVOLUTION. 



A correspondent applied to the 

 editor of the Nation asking " for infor- 

 mation on books relating to the devel- 

 opment or evolution theory, especially 

 for the book ' which is not too partisan 

 or too technical, but gives the facts and 

 reasonings with reference to it on both 



