xlviii NOTES. 



might be assumed for the entire heavens, would thus be 1st mag. 20, 2d 

 mag. 65, 3d mag. 190, 4th mag. 425, 5th mag. 1100, 6th mag. 3200, 7th 

 mag. 13000, 8th mag. 40000, 9th mag. 142000 ; making together, from the 

 1st to the 9th magnitudes inclusive, 200000 stars. If you should object to 

 me, that Lalande (Hist, celeste, p. iv.) gives the number of stars visible to the 

 naked eye, observed by himself, at 6000, I should remark in reply that there 

 are amongst them very many observed more than once ; and that, omitting 

 these, we arrive approximately at only 3800 stars for the part of the heavens 

 comprised by Lalande's observations i. e. between 26 30' and +90. 

 As this is 0'72310 of the entire heavens, the resulting number of stars visible 

 to the naked eye throughout the firmament would again be 5255. A review 

 of the Uranography of Bode, composed from very heterogeneous elements 

 (17240 stars), after deducting nebula and smaller stars, as well as stars of 

 6'7 magnitude raised to the 6th magnitude, gives not above 5600 stars from 

 the 1st to the 6th magnitude inclusive. A similar estimation for the whole 

 heavens, corresponding to the number of stars from the 1st to the 6tb magni- 

 tude inclusive, registered by Lacaille, between the South Pole and the 

 Tropic of Capricorn, confirms also the mean result previously given to you, 

 since it falls between the limits of 3960 and 5900. You see that I have 

 willingly endeavoured to fulfil your wish for a more thorough investigation of 

 the numbers. I may add that Heis, of Aix-la-Chapelle, has been for several 

 years engaged in an exceedingly careful revision' of my Uranometrie. 

 According to the portion of this work which is already completed, and accord- 

 ing to the considerable augmentations which have been made to my Urano- 

 metrie by an observer gifted with more acute vision, I find for the Northern 

 Hemisphere 2836 stars from the 1st to the 6th magnitude inclusive : and 

 hence, on the assumption of equal distribution over the whole firmament, we 

 have again 5672 stars visible to highly acute unassisted vision" (MS. 

 communication from Professor Argelander, March 1850). 



( 171 ) p. 90. Of stars down to the 6th magnitude, Schubert reckoned the 

 number-for the whole heavens at 7000, almost the same as the number 

 assumed by me in the first volume of Cosmos (English edition, p. 140), and 

 for the horizon of Paris above 5000 ; and down to the 9th magnitude inclusive 

 for the whole sphere, 70000 (Astronomic, Th. iii. S. 54). All these numbers 

 are considerably too high. Argelander finds, from the 1st to the 8th magni- 

 tude, only 58000. 



( 172 ) p. 90. " Patrocinatur vastitas cocli, immensa discreta altitudine, in 

 duo atque septuaginta signa. Usec sunt rerum et auimantium effigies, in 



