ASTRONOMY AND METEOROLOGY. 365 



precision as observation would give. M. Leverrier asserts that theory 

 alone does not suffice to represent the total of observations made dur- 

 ing the century just ended, not even if account be made of the 

 influence of all the known masses of our planetary system ; so that to 

 make the new tables accord with the reality of facts, he has been 

 obliged to correct the tables empirically, which operation corresponds 

 to an influence whose real cause has not yet been discovered. " I 

 think I have ground to conclude," said M. Leverrier, " that besides 

 the movement whose cause is known to us, the solar perigee under- 

 goes an oscillation whose amplitude is 60, and the period 66 f years. 

 When we do not stop at the observations of 1755, 1801, and 1845, but 

 consider besides the intermediate determinations, it will be seen that 

 the greatest equation of the centre also presents a slight secular varia- 

 tion ; and further, that the secular variation of that element cannot be 

 entirely produced by the masses at present admitted into the reckon- 

 ing." M. Leverrier thinks the time has not yet come to indulge in 

 conjectures as to the cause of these errors. Other researches, which 

 demand a great deal of time, and which are already commenced, are 

 indispensable to the clearing up of this subject. It may be that we 

 know only a small part of the matter contained in the celestial regions. 



ADVANTAGES OF THE CLIMATE OF PERSIA FOR ASTRONOMICAL 



OBSERVATIONS. 



The following extracts are derived from a letter written by the Rev. 

 Mr. Stodclart, an American missionary, to Sir John Herschel, dated 

 Oroomiah, Persia, October, 1852. " Xo one has ever travelled in this 

 country without being surprised at the distinctness with which distant 

 objects are seen. Mountains fifty, sixty, and even a hundred miles 

 off, are projected with great sharpness of outline on the blue sky : and 

 the snowy peak of Ararat is just as bright and beautiful when two hun- 

 dred miles distant, as when we stand near its base. This wonderful 

 transparency of the atmosphere frequently deceives the inexperienced 

 traveller ; and the clump of trees, indicating a village, which seems to 

 rise only two or three miles before him, he will be often as many hours 

 in reaching. In this connection you will be interested to know that 

 the apparent convergence of the sun's rays, at a point diametrically 

 opposite its disc, which, if I mistake not, Sir David Brewster speaks of 

 as a very rare phenomenon, is here so common that not a week passes 

 in summer, when the whole sky at sunset is not striped with ribbons, 

 very much like the meridians on an artificial globe. But it is after 

 nightfall that our sky appears in its highest brilliancy and beauty. 

 Though accustomed to watch the heavens in different parts of the 

 world, I have never seen anything like the splendor of a Persian sum- 

 mer evening. It is not too much to say that, were it not for the inter- 

 ference of the rnoon, we should have seventy -five nights in the three 

 summer months, superior for purposes of observation to the very finest 

 nights which favor the astronomer in the New World. AVhen I first 

 came here I brought with me a six-foot Newtonian telescope of five 



