374 



KNOWLEDGE. 



September, 1910. 



¥F4 



too late again; so neither the priority- of the 

 theoretical nor the \-isual discovery could be placed 

 to the credit of this country — though England 

 participated in it in some degree. 



^ In the Ast. Nadu, No. 2134 (for 1877) Galle has 

 given a historical account of the visual discovery. 

 He said that in 1845 he had sent Le Verrier a copy 

 of his dissertation, just printed for his doctor's degree'; 

 to this Le Verrier did not reply until he wrote in 

 1846, September 18th, and suggested that Gallc 

 should use the large 

 equatorial and search for 

 the unknown bod\-, and 

 that he would probabI\- 

 detect it by its disc. This 

 letter reached Galle on 

 September 23rd, and he 

 determined to look for it. 

 It was fortunate that the 

 Berlin Observatory pos- 

 sessed a cop\- of the 

 newly - published map — 

 being Bremiker's map for 

 R.A. XXI". Its use was 

 in aiding the almost 

 immediate discover\- of 

 the planet, and, accord- 

 ing to some accounts, 

 it was suggested b^- 

 D'Arrest. Galle used the 

 9J-in. telescope, whilst 

 D'Arrest checked off the 

 objects as Galle observed 

 them. On the evening 

 of September 2ird Galle 

 very soon observed an 

 object, equal to an eighth 

 magnitude star, which 

 was not on the Berlin 

 Academy's charts ; he, 



and Encke afterwards, measured its distance from 

 the surrounding stars and made its diameter to be 

 2"7, which agreed very closely with that calculated 

 by Le Verrier. The longitude heliocentric from 

 observation on September 23rd was 326° 57', and 

 that calculated from Le Verrier's elements was 

 326" , being less than one degree in error — a 

 wonderful accomplishment. Observations bv Galle 

 on September 24th and 25th established beyond an\- 

 doubt the planetary character of the bodv. 



In the same year, 1845, Challis had Iseen stirred, 

 by the public, tion of Le Verrier's memoir in June 



wiM(H.irni'Ly.\K.\DJ'anKDrai>ns&T<:xst'ii.wTKX 



FiGURK 1. 

 Portion of the Berlin Cliart, by means of wtiicli Neptune was 



discovered bv Galle. 



to repeat the process at intervals and compare the 

 results. In this way he hoped to detect anv strange 

 object. On July 29tli he scrutinized the region 

 calculated by Adams, also on July 30th. August 4th, 

 August 12th and later days, but he delayed the 

 comparison of his observations. Oh ! these fatal 

 delay's. Some time later, when the comparison was 

 made, he found that he had actually observed the 

 planet on August 4th — only five days after starting 

 the search — and again on August 12th, of the eighth 



magnitude. He said that 

 he would have undoubted- 

 1)' detected the planet 

 sooner and in a far less 

 laborious manner had he 

 had an}' map with which 

 to compare his observa- 

 tions. Again, on Septem- 

 ber 29th, he observed the 

 planet for the third time, 

 and that time more con- 

 scioush', as he noted one 

 among the 300 stars 

 observed " seems to have 

 a disk," and that was 

 before he had received 

 any intimation from the 

 Continent that the planet 

 had actually been dis- 

 covered by Galle on 

 September 23rd. If 

 priority of publication is 

 to be the ruling spirit in 

 scientific discoveries then 

 England cannot claim, 

 unfortunateh'. mainlv 

 through the action of 

 two men.Airy and Challis, 

 the honour of either 

 discovery just discussed. 



Galle \'isuall\' disco\'ered Neptune. 

 The planet had, however, been observed as a 

 fitar by Lalande so long before as 1795. May 8th 

 and 10th, and by Lamont in 1845, October 25th, 

 and 1846, September 7th and 11th. Correspondence 

 and notes concerning the part that D'Arrest 

 took in the discover\- ma\' be found in the volumes 

 of the Ast. Nach. and CoperJiiciis. 



The planet was not at first called Neptune, but 



Le Verrier, after its discoverer. Galle, in a 



letter to Le Verrier, suggested that the name should be 



Janus. Le Verrier replied that " Le Bureau des 



to use the telescc;je to search for the object, and the Longitudes s'est prononce ici pour Neptune, le signe 



scrutmv was actuallv commenced on July 29th, un trident," and continued " Le nom de Janus 



though, had Adams' calculations been treated more 

 respectfull)-, there is no adequate reason why the 

 search should not have commenced in 1845 

 (September), with the most probable result of Le 

 Verrier and Galle being forestalled both in the theor- 

 etical and visual discovery. Challis's method was to 

 note down the approximate position of all stars in the 

 selected region to the eleventh magnitude, and then 



indiqueroit que cette planete est la derniere du 

 systeme solaire, ce qu'il n'y a aucune raison de 

 croire." 



As mentioned at the beginning of this note 

 (p. 314), J. G. Galle was born on June 9th, 1812, at 

 Pabsthaus b\' Grafenhainichen. between Wittenberg 

 and Bitterfeld, where his father carried on a tar-kiln 

 business. Galle was the eldest of seven children, and 



