50 Statement of. a Plan for 



Committee ; who, alter having examined and approved of it, 

 will cause it to be engraved and published, without waiting 

 for any others. The name of the author will be engraved on 

 it, and any observations that he may have had an opportunity 

 of making, — such as errors of the pen, or of the press, in lists 

 of observations, — on stars observed, but no longer existing, — 

 on variable stars, &c. &c. — will be published in the Memoirs 

 of the Academy. 



The Academy entertain no doubt that the fact of being able 

 to promote, without any expensive apparatus, such a great 

 and useful undertaking, as well as the prospect of discovering 

 new planets even during the construction of the charts, will 

 be sufficient to excite the friends of astronomy to participate 

 in it. Nevertheless, it has been thought proper to announce 

 a reward of 25 Dutch ducats for the author of every chart 

 made according to the plan. 



As the Academy enjoy the privilege of free postage within 

 the limits of the Prussian post, astronomers in addressing 

 the members of the Committee or in sending in their charts, 

 may take advantage of this circumstance. 

 Berlin, Nov. 1, 1825. 



Letter from M. Encke, to J. F. W. Herschel, Esq. 



Berlin, May 19, 1826. 



I hasten to answer the letter of the 29th of April which you 

 were so good as to send me. 1 set too great a value on the in- 

 terest which the Astronomical Society takes in our plan, to delay 

 for a moment giving you all the explanation that you wish for. 



The principal object of the Academy is to procure a know- 

 ledge of the heavens as perfect as the present instruments will 

 enable us to obtain. If in Flamsteed's time we might content 

 ourselves with possessing maps of all the stars as far as the 5th 

 and 6th magnitude, it appears that at the present period we 

 cannot even limit them to those of the 7th and 8th magnitude, 

 but ought to extend them, so as to include in the same sheet 

 all the stars of the 9th magnitude. Or at least, the continual 

 use we make of such stars renders it desirable to possess ob- 

 servations sufficiently correct of all the stars as far as the 9th 

 magnitude inclusive. If we wish to observe such stars in the 

 same manner as Lalande has done in his Histoire Celeste, or 

 Bessel in his Zones, we could never be certain of having ob- 

 served them all, their number being too great. It seems, then, 

 that we should first of all endeavour to procure a knowledge 

 of the whole of the above-mentioned existing stars, more de- 

 tailed 



