Mr. Herschel on Reflecting Telescopes. 293 



whose position and distance are stated at 45° 27 / sf and l".957 

 respectively, while Mr. South's recent measures, which appear 

 entitled to preference, being the results of 19 measures of angle 

 and 10 of distance taken on 4 different nights, and agreeing well 

 together, make the mean result as follows. 



Position 33° 14' sf; Distance l".447; Epoch 1825.59. It seems 

 certain therefore that an error of 10° must have been committed 

 in the reading off of the printed angles. Granting this, the re- 

 maining error of 2° 1 3' would be pardonable in so very close a 

 star as the result of a single set of measures. 



In the remarks I have thought it necessary to make on that 

 part of Mr. Fraunhofer's memoir which refers to the action of re- 

 flecting telescopes, I should be very sorry to have expressed myself 

 in any way capable of being construed in a controversial sense, or 

 as intended to give the slightest personal offence to its celebrated 

 author, who as an artist must surely be ever regarded as a bene- 

 factor to astronomy, while optical science is no less indebted to 

 him as a philosopher, for his beautifully delicate experiments on 

 the constitution of the prismatic spectrum, which have given a 

 degree of precision to optical determinations hitherto unheard of, 

 and shewn the practicability of placing the construction of tele- 

 scopes on purely scientific grounds, while they have unfolded phe- 

 nomena of the highest interest in a speculative point of view. 

 Nor can I help feeling that I should ill requite his liberal and 

 friendly reception during a visit to Munich, which I shall ever re- 

 collect with pleasure^ and in which I had ample opportunity to 

 admire both the resources of his genius and the simplicity of his 

 manners, by a word calculated to give pain or excite unpleasant 

 feelings, 



■ quod vitium procul abfore chartis 



Atque animo prius, ut si quid promittere de me 

 Possum aliud, vere promitto. 



J. F. W. Herschil. 



